JOINT ARMY-NAVY INTELLIGENCE STUDY OF SOUTHWEST JAPAN:

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• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP79-01144A001500010002-3
• Release Decision: RIPPUB
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• Document Creation Date: December 16, 2016
• Document Release Date: December 10, 2004
• Sequence Number: 2
• Publication Date: August 1, 1944
• Content Type: STUDY

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JANIS 84
CHAPTER II
SAKHALIN
OREA
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JOINT ARMY-NAVY INTELLIGENCE STUDY
OF
SOUTHWEST JAPAN:
KO:Ishii, Shikoku, and Southwestern Honshu
MILITARY GEOGRAPHY
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Cover Page
List of Effective Pages and Table of Contents,
Chapter II (inside front cover)
Text and Figures
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List of Effective Pages, Chapter II
SUBJECT MATI'ER
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Table of Contents amid and imprint ( inside back cover, reverse blank) Original
20. INTRODUCTION
21. RELIEF
unnumbered
pp. II - 1 to II - 42
p. II - 43
Figure II - 53
Figure II 54
Figure II - 56
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Figure II 62
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Figure II -80
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Figure II -84
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Table of Contents
Note: This chapter is based upon material available in Washington, D. C., on 1 AuAust 1944.
Page
i:t- 1
II- 1
A. General: II - 1
B. Relief regions: Kyfishu II - 1
) Southern KyUshfi Lowlands and Highlands II- 2
(2) Central Kyushu Mountains II - 3
(3) Northern Kyfishia Lowlands and Highlands II - 5
(4) Northwestern Kyushu Broken Lands II - 7
C. Relief regions: Shikoku II - 8
(1) Southwestern Shikoku Broken Lands
? II- 8
(2) Central Shikoku Mountains
? II 8
(3) Kochi Plain II - 9
(4) Eastern Shikoku Plain II - 9
( 5 ) Northern Shikoku Lowlands II - 10
D. Relief regions: West Central Honshii II - 10
(1) Kii-hanto Mountain Land II - 11
(2) Kinki Region Lowlands and Highlands . . . II - 11
(3) Ise-wan Lowlands . . . H - 16
(4) Hainamatsu-Toyohashi Coastal Lowland . . II - 17
(5) Central Honshil Rugged Highlands II - 18
E. Western Honshu
(1) Tamba Broken Plateau . . .
(2) Maisue-Tottori Coastal Lowlands .
(3) Western Honshii Rugged Highlands
(4) Western Honshu Broken Lands
(5) Himeji-Yashiro Lowland
22. DRAINAGE AND WATER SUPPLY
A. General
B. Rivers
(.1) Upper reach
(2) Middle reaches
(3) Lower reach
(4) Canalization
C. Lakes
23. SOIL TRAFFICABILITY
Speentiat
"C
A. General factors affecting soil trafficability
B Soil trafficability by regions and seasons
(1) Kyushu
(2) Shikoku
II - 26
(3) Western Honshi) south of central mountain ranges II - 26
(4) Western Honshti north of central mountain ranges 11- 26
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II - 22
II - 22
II - 22
II 23
II - 23
II - 24
II -24
11-24
II - 24
II - 25
II - 25
11 -26
IT '?6
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Chapter II
Page 11- I
MILITARY GEOGRAPHY
20. Introduction
This chapter describes the terrain of Southwest Japan,
emphasizing the influences such terrain would have on military
operations. The principal topics discussed are relief, drainage,
soil trafficability, and vegetation. Because of the diversity of
the terrain, particularly relief, in Southwest Japan, the topical
paragraphs which follow, with the exception of drainage, are
treated regionally. The regions (EIGuRE II - 107) have been set
up in 3 rough categories:
AREAS IN WHICH MOVEMENT IS LEAST DIFFICULT. This type of
region includes plains and associated basin and valley networks
more than 5 miles in extent. Movement to most parts is over low
grades, less than 10%. In the uplands which surround the tribu-
tary valleys and basins there are many commanding heights which
overlook the lowland strips. Passes in these highlands are gener-
ally below 1,500 feet elevation.
AREAS IN WHICH MOVEMENT IS DIFFICULT. These regions con-
sist of many basins and valleys but are. without large plains. In
some places the valleys form complete nets. Most of the area has
slopes exceeding 30%, but some routes with less steep slopes are
available. These routes are few in number, are restricted, and have
many commanding heights. Passes are generally above 1,500 feet.
AREAS IN WHICH MOVEMENT IS VERY DIFFICULT. Rugged up-
lands predominate, with only single or short disconnected valley
and basin routes available. Nearly all of the area has slopes in
excess of 30%. Passes are generally above 1,500 feet.
A brief summary of the terrain characteristics of the entire
area is given in CHAPTER I, TOPIC 2. Somewhat more
detailed information can be obtained in the "A" or general
sections of TOPICS 21, 22, 23, 24, 26, and 27 which follow.
TOPIC 25 is a summary table giving the bare essentials of the
terrain for each terrain region and sub-region.
Much detailed terrain information may be derived by careful
use of the hypsometric map (PLAN 38), the slope maps.
(PLANS 39 and 40), and the vegetation maps (PLANS 41 and
42). The slope and vegetation maps contain a detailed natural
drainage pattern. Canals and irrigation ponds are not shown on
these maps, but can be located on individual Japanese General
Staff topographic maps, scale 1:50,000. Additional textual de-
scriptions of certain areas can be obtained from the sources
listed in Paragraph 28, and from other chapters, particularly
Chapters IV, VII, and IX.
21. Relief
A. General.
The relief of Southwest Japan* is characterized by great
variety of landforms and complex arrangement. Most of the
area has rugged or steep-sided block uplands, difficult to pene-
trate. Scattered among and at the borders of these uplands are
small basins or coastal lowlands. These lower lands contain the
main settlements, and are the main military objectives in South-
west Japan. Most of these lowland pockets are protected from
surface attack by great outer barriers of highland. Only those of
southeastern Kyushu, southern Shikoku, and southern Honshu
There may be some difference between spellings of place names in
the text and on maps. Correct spellings are given in the Gazetteer, Chapter XV.
east of the Kii-hantO ( peninsula) are exposed to direct am-
phibious attack from the Pacific. The Nagoya Plain of Honshu
is the largest of these exposed lowlands, but is somewhat pro-
tected by the shallows of Ise-wan (bay), and the hills which
overlook the mouth of the bay. East of Nagoya, the Hamamatsu
coast is entirely exposed. Because of the ruggedness of the up-
lands and the small size of the scattered lowlands, there is only
limited room for deployment; cross-country movement is diffi-
cult everywhere except on the larger plains. Even on the plains,
however, mobile operations are handicapped seriously by the
muddy rice fields, and the numerous streams and farm hamlets.
Most valleys and other natural passages between the larger
lowlands are difficult to traverse, and have numerous places
where strong defense lines could be established.
The major relief features of Southwest Japan are arranged
roughly in 3 parallel lines which extend southwest - northeast
following the main trend of this part of the Japanese Islands.
The 2 outer lines are predominantly uplands; the inner line is
largely a series of basins and small plains. Sections of the
northern and southern uplands, together with the central part
of the lowland belt, have sunk below sea level thus forming
the Inland Sea and separating Kyushu and Shikoku from Hon-
shu. East of the inland Sea, another low break in the southern
upland belt is occupied by Ise-wan. The eastern and western
sections of the interior belt of lowlands, in northern Kyiishii
and west central Honshu, consist of numerous small coastal
plains and basins separated by low but rugged uplands. These
basins are the most extensive lowlands in Southwest Japan and
are densely settled and intensively developed. Small coastal
plains are scattered along the outer flanks of the 2 great up-
land belts, and a few small basins are found within the high-
lands. Few of these lowlands are interconnected by easily pass-
able natural routes. Landforms within the upland belts vary
from low rugged hills of 600-1,000 feet to plateaus and moun-
tains of 2,500-5,000 feet, with some peaks reaching 8,000-
10,000 feet (PLAN 38). Most hills and mountains are rela-
tively steep-sided and sharp-crested although some, especially
in central Kviishii, have smoother surfaces of lava or volcanic
ash. Almost all uplands are forested, or arc in grass and scrub.
All lowlands and most valleys and flattish uplands arc inten-
sively cultivated. Wet rice fields occupy a large part of the
crop area on the plains and in the larger valleys.
In the following sections the terrain regions of Southwest
Japan are grouped into 4 divisions (FIGURE TT - 107) : KyUshil,
Shikoku. West Central Honshu (cast of line from Kobe to
Tsuruga) and Western Honshu (west of the Kobe-Tsuruga
line). Within each of these divisions the major regions are
described in an approximately counter-clockwise order. Each
major region is 'first treated as a whole, then the more critical
areas are discussed in greater detail.
B. Relief regions: Kyushu.
KyUslyil and its western fringe of smaller islands form a
quadrangle 200 miles north - south by 120 to 160 miles east -
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MILITARY GEOGRAPHY onfideptial
west (FIGURE Ii - 108). On the northwest the Goth-retta
(chain) extends an additional 35 miles westward. Central
Kyushu is occupied by rugged barrier mountains of moderate
height which are part of the southern upland belt of Southwest
Japan. This highland belt extends southwest - northeast across
the island between 32?N and 33? N. To the north and south
of the central mountains, small plains and basins alternate with
low rugged mountains, hills, and steep-sided plateau blocks.
Most of the small plains are interconnected by narrow lowlands
or relatively smooth upland strips, but no easily passable nat-
ural routes extend north - south across. or around the central
mountains. Several sections of the central mountains, and large
parts of the regions to the north and south are covered with
a thick layer of volcanic ash. The ash cover smooths some
slopes, but even small streams cut deep, steep-sided valleys in
the light material. These numerous valleys greatly increase the
difficulty of cross-country travel.
( I ) Southern Kyushu Lowlands and Highlands.
The Southern Kyushu Lowlands and Highlands I.ie south of
a line extending northeast from the Sendai-kawa (river) on
the west coast to Nobeoka on the east coast (FIGURE II 1 (7 ) .
Within the regions are 3 large lowlands, described in some
detail below, and many small basins. The 3 large lowlands are
the Makurazaki-Kushikino Coastal Plain on the west, the
Ariake-wan (bay) - Miyakonojo Lowland on the south, and
the Miyazaki-Nobeoka Coastal Plain on the east (FIGURE
Ii - 107) These large lowlands are from 3 to 10 miles wide and
20 to 50 miles long; they are connected by a series
of fairly level but narrow and winding valleys and flat
ridge tops which form an irregular line around the northern
end of Kagoshima-wan (bay) and eastward through the Miya-
konojCi Basin to-the Miyazaki Plain. The passageways between
lowlands are 1../Z to 5 miles wide, and 10 to 50 miles in length.
Upland areas of Southern Kyushu vary in form but are
mostly low, rugged mountains and hills, and flat-topped, steep-
sided ridges and plateau blocks. Elevations of mountains and
plateaus are from 1,500 to 2,500 feet, but a few peaks, -mostly
volcanoes, reach 3,500 to -5,500 feet (FIGURE II - 1). These
upland areas, although numerous, are individually small,
FIGURE II- 1. Kirishima volcano. Southern Kyushu.
Kirishima volcano, rising above the plateau of Southern Kyrishil.
Note bare slopes in background and scrub vegetation in
fo::eground. Dry stream bed in middle foreground.
March 1914.
usually less than 25 miles in extent. Some of the uplands con-
sist mostly of granite and have a rounded appearance.
A layer of volcanic ash, 10 to 100 feet thick, covers much of
the western part of Southern Kyushu. Railways and roads are
cut down 6 to 20 feet into this loose material and the cuts have
almost vertical side walls. Other soils on the uplands are rocky
with some clay on the more nearly level areas. The non-ash
lowland soils, found chiefly in the east, are largely loam and
clay.
Vegetation on the lowlands is a mixture of wet-field rice,
dry-field crops, and strips of woodland. The uplands have
patches of dry-field crops on the lower flatter areas, and have
forests of mixed broadleaf-needleleaf trees on the remainder.
Peaks above 4,000-5,000 feet have some bare slopes. Under-
growth is dense in some of the forested sections.
(a) Makurazaki-Kushikino (Satsuma) Coastal Lowland.
This lowland belt consists of 2 small coastal plains joined by 2
low narrow valleys. One plain extends 11 miles east from Ma-
kurazaki town along the south coast of the Satsuma-hant6
(peninsula). The other plain extends 24 miles south from
Kushikino village along the west coast of the peninsula. The
connecting valley sections, north of Makurazaki, are only 6
miles long (Route 11).* The southern, or Makurazaki, Low-
land is triangular, and varies from 2 to 6 miles in width; it is
flattish to gently rolling. The Kushikino Plain, farther north-
west, is long and narrow, it has scattered sand dunes along the
coast; at its northern end hill spurs approach to within a few
hundred yards of the sea. Both plains are in crops, chiefly wet-
field rice on the western plain and dry-field crops on the south-
ern. Inland, separating the 2 lowlands from Kagoshima-wan
(bay), are rugged hills 300-800 feet high; these are penetrated
by narrow winding valleys (RouTE 10). Surface materials on
the plains are chiefly volcanic ash and clay loam; on the hills are
clay and loose rock. Hill lands have a dense forest of mixed
broadleaf and conifers. The plains and valleys have patches of
woodland among the cultivated fields and on the sand dunes.
Cross-country movement is relatively easy across the plains.
except on the rice fields when they are flooded from May to
August. The dune areas along the west coast, and the hills back
of the plains offer poor possibilities for movement due to the
steep slopes and loose sand-ash soils.
(b) Ariake-Miyakonojo Lowland. The main parts of this
area are 2 small lowlands lying respectively west and north of
the head of Ariake-wan (bay) and connected by narrow val-
leys. The western or Ariake Coastal Plain is nearly square, 10 by
10 miles. From its northeastern corner narrow valleys lead
northward through low hill land to the Miyakonoji5 Basin
which is 6 miles wide and 10 miles long (RouTE 1). Both
lowlands have floors which consist of a series of flat terraces.
Major streams have cut valleys 20-100 feet deep across the ter
races thus dividing them into large level blocks which average
to 2 miles in width. These flat areas are in crops, chiefly v,,2t-
field rice in the Miyakonoja Basin and dry crops on the Ariake
Plain. Deployment and movement is easiest on the level areas
in the lowlands from late August to early May, when the rice
fields are not flooded. Patches of woodland are scattered
throughout the plains, and dense forest covers the surrounding
The index to natural routes is shown in FIGURE II - 53. Details for
individual routes are given in FIGURES II - 54 through IT - 106.
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hills and low mountains. Although part of the Ariake Plain has
clay-sand soils, most of it, as well as all of the Miyakonoyi
Basin and the uplands to the north and west, are mantled with
a deep layer of loose, medium-textured volcanic ash.
The western gateway of the Ariake Plain is difficult to use
because a narrow, 1 to 4 mile, belt of hills separates the low-
land from the east shore of Kagoshima-wan (bay). Low nar-
row valleys leading from the plain to the bay are the only
means of exit, because the hills are 200 to 500 feet high and
have steep sides covered with loose ash. The best western
approach to the Ariake-Miyakonojo Lowland is by way of the
flat-topped, ash-covered ridge which occupies most of the area
between Miyakonojo Basin and the head of Kagoshima-wan
(ROUTE 2). The central 4 miles of this 12 mile passageway
is obstructed by rugged hills, 500 to 1,000 feet high. Several
deep narrow valleys cross the hills. Movement is easy on the
flat ash ridges but is moderately difficult in the winding valleys
of the hilly areas. Many parts of the valleys are within machine
gun range of adjacent hills. A northeastern gateway connects
the Miyakonojo Basin and the south end of the Miyazaki-
Nobeoka Coastal Plain (ROUTE 1). Across this route is a
I 0- to 12-mile belt of low, moderately steep, heavily forested,
ash-covered hills. These rise 600 to 700 feet above the valleys.
The railway and most roads avoid the deeper valleys and cross
the hill divides by means of tunnels or deep cuts in the volcanic
ash. Cross-country movement is difficult.
(c) Miyazaki-Nobeoka Coastal Plains. These coastal
plains are almost adjacent to each other, and extend along the
southeast coast of Kyilshil from 31050'N to 32?35'N, nearly
52 miles. The 2 plains are separated by a 12-mile belt of low
hill land north of Mimizu village, 32?20'N (RouTE 1). Each
plain has good beaches, level areas covered with wet rice fields,
and valleys leading inland to difficult passes in the central
mountains (ROUTES 3 and 4). Thus, although the plains are
accessible, and are large and flat enough to permit limited de-
ployment and cross-country movement, they do not have good
outlets inland across the Central Kyushu Mountains.
The Miyazaki Plain is triangular, 33 miles long, and from
5 to 6 miles wide in the south, and 1/2 to 1 mile wide in the
north. Its floor consists of a series of fiat terraces 1/2 to 11/7
miles wide and aligned north - south, the highest terraces being
farthest inland. The terraces are cut into 1- to 2-mile blocks
by streams from the highlands on the west. The wider stream
valleys and most of the flat blocks are covered with paddy
fields which are flooded most of the time from May to August.
Edges of terraces and hill spurs which project onto the plains
are covered with mixed grass and woodland. Farther inland are
low mountains, 1,000 to 2,500 feet in elevation, and covered
with dense forest. Soils in the Mivo7q14 Plain ore chiefly loom
and clay on the flats, with sandy and rocky soils on the hilly
areas.
The Nobeoka Plain is a small triangle 3 by 7 miles, com-
posed of the combined deltas of the Gokase-gawa (river) and
the Kita-kawa. On the deltas are numerous flat wedge-shaped
areas, 1/2 to 1 mile wide, which are separated by the lower
channels of the rivers. Wet rice fields occupy almost all the
flat areas; small grassy glades and dense woods occupy the re-
maining delta land and the surrounding hills. Soils, chiefly clay
and clay loam, are sticky when wet.
The southern outlet, between the Miyazaki Plain, and the
Miyakonojoi Basin has been discussed in connection with the
latter lowland (Route 1). The only western outlet of the Miya-
zaki Plain which is even moderately passable is the Hitotsuse-
gawa valley which connects with the Hitoyoshi Basin in the
Central Kytashil Mountains (ROUTE 3). The Hitotsuse-gawa
valley is very narrow, 500-800 feet, and has many sharp bends.
Commanding heights rise 200 to 1,000 feet above these turns.
Another route follows the winding Gokase-gawa valley west-
ward from Nobeoka. This route is similar to the Hitotsuse-
gawa valley but is slightly wider, 1,000 to 1,200 feet (RouTE
4). Northward from Nobeoka the narrow, irregular Kita-kawa
valley leads through low mountains; it affords a poor passage-
way to Saeki on Saeki-wan (ROUTE 1). The railway which
follows this route uses numerous short tunnels in crossing the
rougher part of the uplands.
(2) Central Kyishii, Mountains.
This region consists of a southern belt of moderately high,
rugged mountains, aligned southwest - northeast across the
island between 320 and 33 'NT, 'and a northern area of slightly
lower and less rugged plateaus and hills, which extend almost
to the northern end of the island (PLAN 38). Although the
uplands are not high, averaging 3,000 to 4,000 feet in the
south and 1,800 to 3,000 feet in the north, they are serious
barriers to cross-country movement. Even the best natural
passageways through the mountains have many places where
strong defensive positions could be established. No easy, or
only moderately difficult, natural routes entirely cross the moun-
tains from northwest to southeast. One moderately difficult
passageway crosses the upland from west to east by way of
Aso-zan (mountain) crater and the Ono-gawa (river) valley
(ROUTE 5). This passageway follows the dividing line be-
tween the mountainous section and the rugged plateau and
hilly section.
Within the southern, rugged mountain section of the Central
Kyushu Mountains deployment and cross-country movement
are extremely difficult except in the isolated Hitoyoshi Basin
on the upper Kuma-gawa. Almost all conditions of the terrain
handicap these operations. Slopes everywhere are steep. Except
in the Hitoyoshi Basin, flattish areas are few and tiny. Stream
valleys are crooked and narrow; and many commanding heights
rise 1,000 to 1,600 feet above the valley bottoms. Most peaks
reach 3,500-4,000 feet, and a few, mostly volcanoes, reach
5,000 feet. The southwestern and northern flanks of the south.
ern rugged mountains are covered with a deep, 50 to 100 foot,
layer of loose volcanic ash. Other surface materials are chiefly
loose rock on the highest slopes and rock mixed with clay on
the lower slopes. A dense forest with heavy undergrowth occu-
pies all but the northern slopes and highest areas, as well as
the area around Aso-zan (mountain) where coarse grass grows
on the fresh ash (FIGURE II - 2).
The Hitoyoshi Basin is an oblong depression which trends
roughly east - west along the upper Kuma-gawa. (river). The
basin is 7 miles wide and 18 miles long, but only the 3- to 4-
mile-wide belt south of the river has a flat surface. Here the clay
and loam soils are planted chiefly with wet-field rice, but there
are small areas used for dry crops. Tributary streams have cut
shallow valleys in the basin floor, dividing it into flat blocks
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MILITARY GEOGRAPHY
Vitality, 11- 2. Aso-zan, Central Kyrtsbit.
Much 4 the land near Aso-zan is suitable for military operations;
slopes are low and vegetation is mostly coarse grass.
measuring I to 2 miles across. Landing strips might be con-
structed on these blocks. The lower Kuma-gawa, below the
outlet from the basin, runs througlt a deep, narrow, winding
valley which has numerous commanding heights and extreme
narrows ( RouTF, 3).
The Aso-zan - Ono-gawa (rifer) passageway across the Cen-
tral kyitsina Ntountains is the least difficult route through the
upland (ROUTE 5). The western part of the route, leading into
and through the crater of Aso-zan, is level or gently sloping
and is fairly wide (FIGURE II - 2). This section is well-drained,
except for the rice fields on the crater floor. These rice fields
are flooded from .lune to August and are muddy all the year
(1,1fctuttE U- 3). The steep grade up the east wall of Aso-zan
crater is very difficult for several miles. The long outer eastern
slope of the crater is gentle, but is covered with fresh loose ash
on which a coarse grass grows. Many valleys are cut deeply into
this ash slope but are parallel to the route. This drainage pat-
tern blocks extensive deployment on either side of the route,
but does not interfere seriously with cast - west movement
.dong the route. East of the outer ash slopes of Aso-zan, the
Ono-gawa valley ( Ft0uRt, Ti - 4) extends northeastward to
Beppu-wan (bay). The Ono valley, only moderately wide at
the bottom, is fairly deep, and winding. Several strong defen-
sive positions may be set up facing either up or down stream
FIGUEE Ti - 5). These could take advantage of commanding
heights and of forest cover. Most of the Ono valley slopes and
the surrounding hills are covered by a deep ash soil. Coarse
grass is the chief type of vegetation. Rice fields and woodlands
occupy roost of the lower Ono valley and the small Beppu
coastal plain. A railway follows the Aso-zan - Ono-gawa route
all the way:, and a road parallels the railway.
The northern arm of the Central Kyushu Mountains is a
series of broken lava plateaus of moderate height, 1,500 'to
3,000 feet, with scattered volcfnic peaks which reach 4,000 to
i,000 feet, Most valleys are cut down 800 to 1,000 feet below
the adjacent plateau masses. Few of thc plateau blocks have
flat tops more than a half mile in extent; most of these areas
have been reduced to valley slopes. The valleys arc winding
and narrow at the bottom (FIGURE ti - 6). Movement along
the valleys is difficult and there is no room for deployment
within the uplands. At the northeastern edge of the region are
narrow coastdi plains or sills. Pockets of fairly level alluvium
have accumulated on these narrow plains where rivers come
clown to Beppu-wan (bay) and to the Suo-nada (sea) coast
hicahoi II 3. Aso-2an. Central Kyiti-hn.
Cultivated land at the foot of Aso-zan.
FiGuRE II -4. Beppn, Central KyRshrt.
Beppu is located on a small plain backed by steep hills and mountiens.
The OnaLgawa valley leads from this plain southwestward
through he mountains to Aso-zan. Looking NW, 1935.
FiGuRii II - 5. Beppa, Central Kyrishrt.
Looking SE. Rice field on upland behind Beppu. Enemy positions
established on such terraces would be difficult to reach.
Note abrupt coastline in background.
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FIGURE II - 7. Dazaita, Northern Kyrishri.
Near Entsukaichi, Kyfishit; showing terrain on the best
route between Fukuoka and Saga.
FIGURE II - 6. Yabakei, Central Kyfishft.
Typical valley route in Kyfishil Such routes can be blocked easily
and the road destroyed. Note highway tunnels at right, and
railroad bridge in middle background.
near Nakatsu and Nagasu. Each compartment of these tiny
coastal lowlands is less than 5 miles across and is broken by
stream channels and ditches leading to the wet rice fields.
Moderately heavy forest covers most of the area which is not
in crops, although a belt of grassy uplands extends northeast-
ward from Aso-zan to Beppu-wan. The southern part near Aso-
zan (mountain peak) has a deep volcanic ash soil. Elsewhere
rocky clay soils prevail in the uplands, and clay and loam in the
larger valleys and on the coastal sills.
(3) Northern Kyushu Lowlands and Highlands.
This is a long narrow region, 100 by 25 miles, lying north
and west of the Central Kyushfi. Mountains and extending
northeast - southwest from Shimonoseki-kaikyo (strait) to the
head of Yatsushiro-wan (hay). Dominant types of relief are
low rugged mountains and hills, and flattish lowlands.
The most significant terrain areas are a series of intercon-
nected lowlands aligned north - south through the center of the
region and flanked on the northeast and northwest by low but
rugged uplands. Short but strategic valleys penetrate the north-
eastern upland; and narrow but equally significant coastal low-
lands separate it from Shimonoseki-kaiky6 (strait). The larger
lowlands are the Kumamoto and Saga Coastal Plains on the
south, and Fukuoka Plain facing Fukuoka-wan (hay) on the
north.
FIGURE II - 8. Karatsu, Northern Kyushu.
Road mounting steep slope in Northern Kyushfi. Note flooded
paddy fields in background, and sparsely forested slopes.
The Saga and Kumamoto Lowlands are exceptionally large
for Kyushu. Deployment is possible and cross-country move-
ment is relatively easy within the lowlands and along the sev-
eral passageways which connect them. These southern plains
arc roughly quadrilateral; the Kumamoto Plain measures 26
by II miles and the Saga Plain is 31 by 16 miles. The Saga
and Fukuoka Lowlands are joined by a corridor at Futsukaichi
(ROUTE 10b and FIGURE II - 7 ) . The Fukuoka Plain and the
Fukuoka-Saga corridor are connected with the narrow Yawata-
Shimonoseki Coastal Lowland and the Onga-kawa (river) basin
by short but steep and crooked routes across spurs of the north-
eastern highland (RourEs 7 and 10). These routes follow
flat valleys most of the way but can be blocked easily in the
rugged sections.
The northwestern or Seburu upland is a low rugged broken
hill and mountain land. Its numerous valleys are narrow and
crooked. From them steep slopes rise to sharp crests, 1,500 to
3,000 feet high. Many roads and trails cross the upland north -
south but all have sharp bends and steep grades, and may be
blocked at many points (FIGURE Ii - 8). Most of the surface
material in the northwestern, or Seburu, upland is clay mixed
with sand and loose rock. The vegetation is dominantly forest
in the eastern half of the upland and coarse grass in the west.
Wet-field rice and some dry crops occupy the valleys and small
basins.
The northeastern, or Chikuh6 upland, consists of irregular
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and widely spaced ranges of low mountains between which are
lower, scattered ranges of hills. Many flat-bottomed valleys
deeply penetrate, but do not cross, the hill belts. Elevations
reach 600 to 1,000 feet in the hills, and 1,600 to 2,500 feet
in the mountains. Most mountain slopes are steep? but the
hillsides have only moderate inclinations. Both these types of
terrain have rocky,. sandy soils and forest cover with scattered
grassy areas. Valleys have clay and loam soils, which are inten-
sively cropped. Wet-field rice predominates. Deployment with-
in this area would be limited to the broader valleys, such as
the upper Chiku.gii and lower Onga, which are 1 to 3 miles
wide. Cross-country movement is difficult on the sloping, for-
ested, high ground., but is relatively easy in the valleys, par-
ticularly when the rice fields are driest, from October to late
June or July. The broader valleys do not extend entirely across
the region. Upper sections of the valleys, near passes, although
nearly level and straight, are also narrow. Commanding heights
rise 600 to 1,000 feet above these narrow valleys.
(a) Saga Plain. This is the largest lowland on Kyushu
Island. It extends 31 miles northeast - southwest, from the
Futsukaichl corridor past Saga city to the head of Ariakeno-
umi (sea), and 16 miles northwest - southeast along the cast
side of Ariakeno-umi. Inland near Kurume city the plain nar-
rows to 6 miles, but widens to 12 miles farther northeast.
The plain is nearly flat, and is divided into 1/2- to 2-mile
blocks of wet rice land by a complex grid of stream channels
and artificial ditches. 'The larger ditches and streams are signifi-
cant barriers at all seasons, and would have to be bridged in
order to handle most types of field equipment. On the rice paddy
fields between these barriers deployment and cross-country
movements are easiest from September to June when water and
mud are at a minimum. Operations also would be influenced
somewhat by the small settlements of farm dwellings which are
scattered over the plain at intervals of l/2 to 3/, mile. Each
hamlet contains 10 to 40 dwelling units (house with attached
buildings) made chiefly of wood and averaging 15 to 20 feet
in height.
Chief land gateways to the plain are the Futsukaichi cor-
ridor to the Fukuoka Plain on the north, and winding valleys
through low but rugged hill land southward to Kumamoto
and westward to Sasebo (ROUTE'S 9, 10, 10a, and 101)). The
Futsukaichi corridor has been discussed under the Northern
Kyushu Lowlands and Hills Region (R.ouTE lob). The
southern gateway consists of a narrow coastal plain or sill,
along Ariakeno-umi (sea), and 3 alternate inland routes
through rugged hills. The length of these routes varies from
30 to 5 miles. The coast route deviates inland just north of
Kumamoto city to avoid an isolated mass of low, 2,000 feet,
mountains which reach the coast at that point (ROUTE 10a)
North of this upland mass the coastal plain is 11/2 to 1. 11/2 miles
wide, flat, covered with wet rice fields, and crossed by many
streams (FrsuRE 1.1-9). The inland routes follow valleys
which vary in width from 400 feet to 2 miles (Rou'rE .10).
The narrow sections of these routes are winding, and a few
parts are steep. The adjacent heavily forested heights rise steeply
-400 to 1,000 feet above the valleys..
The western outlet of the Saga Plain leads westward across
the narrowest part of the plain from Saga to Ushizu and from
there extends west 35 miles to Sasebo in Northwestern Kyia-
sir(' (ROUTES 8 and 9). The first 12 miles west of Ushizu,
as far as Takeo, is along the flat, mile-wide valley of the Rok-
kaku-gawa. Westward from Takeo the route leads 23 miles
through the low but rugged hills of Northwestern Kyushu,
A second narrow passageway leads northwestward from
Ushizu to Karatsu through similarly rugged country.
FIGURE II - 9. Baramanda, Northern Kyrish.
Looking E. Part of coastal route between Saga and Kunlamoto.
Note low hills rising out of plain at right.
(b) Kumamoto Plain. This lowland extends 25 miles
north - south and 11 to 12 miles east - west. North of Kuma-
moto city it is separated from Ariakeno-umi (sea) by a south-
ern extension of the rugged lands between Saga and Kumamoto
Plains. South of Kumamoto the plain faces Ariakeno-umi for 6
miles. South of Udo village a 5 mile wide coastal plain forms a
short, 18 mile, corridor along the east side of Yatsushiro-wan
(RouTE 10). This Yatsushiro corridor ends abruptly against
the northern flank of the Central Kyushu Mountains.
Yatsushiro corridor and the coastal delta area southwest of
Kumamoto city are flat and covered with a grid of wet rice
fields separated by streams and drainage ditches, as in the Saga
Plain to the north. Near Kumamoto, however, the streams
are even more numerous, and the flat areas are only 1/2' to 11/2
miles across. Farm hamlets are I/2 to :3/;, mile apart as on the
Saga Plain. Soils of the southern Kumamoto Plain are sandy
clay with much volcanic ash intermixed. The central section of
the plain, north and east of Kumamoto city, is part of the long,
gentle* western slope of Aso-zan (mountain). (FIGURE II - 2).
This gently sloping, ash-covered part of the plain is cut into a
series of almost flat-topped, fan-shaped segments by the broad
shallow valleys of streams flowing down Aso-zan. The valleys
are 11/4 to 1 mile wide and their flat bottoms are in wet-field
rice. Much of the volcanic ash surface of the dry flats between
streams is covered with trees, but other parts of these inter-
stream areas are in grass and dry-field crops and are suitable
for cross-country movement. Almost all the farm hamlets are
found in or near the shallow valleys. At the northern end of
the _Kumamoto Plain wet rice fields occupy a large area in the
broad valley of the upper Kikuchi-gawa (river). Flat segments
of ash-covered plain which lie between branches of the river
are planted with trees and dry-field crops.
The only short and easily traversed gateway to the Kuma-
moto Plain is the multiple route north to the Saga Plain
(ROUTES 10 and 10a). This route has already been discussed
in connection with the Saga Plain. The only other approaches
to the Kumamoto Lowland are 2 mountain valley and basin
' See slope scale on PLAN 39.
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routes across the rugged Central Kyushu Mountains. These 2
difficult passageways are the Ono-gawa - Aso-zan route from
the east and the Kuma-gawa - Hitoyoshi Basin route from
the south (ROUTES 3 and 5). Both have been treated in con-
nection with the Central Kyushu Mountains.
(c) Northeast Coastal Lowlands and Hills. This narrow
interrupted belt of lowlands includes the Fukuoka Plain on the
west, and curves around the northern end of the Chikuhb up-
land to include the small Yukihashi coastal plain on the Sub-
nada (sea) arm of the Inland Sea. The lowland strip varies in
width from 9 miles at Fukuoka-wan (bay) on the west to an
average of I/2 to 1 mile at the industrial-urban belt between
Wakamatsu and Kokura (in the center) and then widens to 5
miles at Yukihashi on the east. At 2 points, the base of Moji-
hantii (peninsula) and between Tobata city and the Onga-
gawa (river), the lowland lies inland behind the coastal hill
ranges. Low hill spurs cut completely across the lowland at
several points in the section between Fukuoka-wan and the
mouth of the Onga-gawa. To avoid these, the main highway and
the railway follow a series of transverse valleys 4 to 5 miles
inland (RouTE 8). The Northeast Coastal region, though
small and broken, is important. It contains the largest region
of heavy industries in Japan (Yawata-Tobata district); it con-
trols the western, or Shimonoseki-kaikyo (strait), entrance to
the Inland Sea; it is one of the nearest points to the Asiatic
mainland, in Korea; and its western section has one of the
largest groups of good landing beaches in Kyushu. This is one
of the critical areas of Southwest Japan.
The westernmost, or Fukuoka, plain and the easternmost, or
Yukihashi, plain are occupied almost completely by wet rice
fields. These flat fields are flooded or have deep mud from July
to October. The rice field areas are divided into blocks 1 to 2
miles in extent by streams which flow out from the uplands.
Most of the lowlands between Fukuoka and Yukihashi are
narrow but are covered also with wet rice fields. Exceptions arc
the sand dune areas on the beaches which have coarse grass
or small needleleaf trees, and the built-up urbanized strip be-
tween Yawata and Kokura. Lower hill slopes are terraced and
occupied by dry-field crops and some irrigated rice; upper hill
slopes are in forest with open grassy areas. Soils are mostly
clays and clay barns.
Chief land approaches to the North Coastal Lowlands are
westward along the Sub-nada coast from Nakatsu and north-
ward through the natural Futsukaichi corridor from the Saga
Plain. The approach from Nakatsu is a narrow coastal plain
4 to 5 miles wide, occupied by wet rice and dry crop fields, and
cut transversely by many streams from the mountains. A rail-
way and highway use this route (RouTE 1). The easiest and
most used gateway is the Futsukaichi corridor (ROUTE 10 and
0b). This passageway narrows to 3/, mile near Futsukaichi
village but widens rapidly north and south to 5 miles. The cor-
ridor has a flat floor of loamy soil which is occupied almost
completely by wet rice fields (FIGURE II - 7). Two railway
lines and 2 highways use the passageway and all pass through
Futsukaichi. Hills on either side of the corridor rise 300 to 900
feet within 9 miles. They are covered with grass and some
patches of woodland. A highway and a railway turn north from
a point near Futsukaichi and cross the hills and low mountains
to the upper Onga-gawa valley (ROUTE 10). These routes are
much used but do not afford a good military passageway be-
cause they have many turns and steep grades in the rugged
10-mile section across the divide. The railway uses several tun-
nels; one, under the divide, is nearly a mile long.
The only other approach to the North Coastal Lowlands is
the road and rail route eastward along the seacoast from Ka-
ratsu to Fukuoka (RouTE 8). A large part of this route is a
1- to 5-mile wide coastal plain covered with wet rice fields, and
is similar to the coastal lowland east of the Fukuoka Plain.
The chief handicap is a 5-mile section east of Hamasaki. There
steep slopes and cliffs rise 300 to 500 feet above the shore. The
road and rail beds are cut through numerous rocky headlands.
Seven short tunnels are used by the railway in passing this
5-mile section.
(4) Northwestern Kyfishfi Broken Lands,
This region includes the long irregular peninsula north and
west of Ariakeno-umi (sea), and the adjacent islands. The
main islands and groups of islands arc the Amakusa-jima and
nearby islands on the south, the Goto-retto (chain) on the
west, and iki-shima on the north. The peninsula, with its imme-
diately adjacent islands and its inshore waters, extends 70 miles
north - south by 40 miles east - west. The Amakusa group
measures 40 miles along the northeast - southwest axis and
averages 18 miles in width (northwest - southeast). Similar in
orientation, but of less width, is the Goto-rettO, 57 by 11
Iki-shima, 16 miles offshore, is nearly square, 11 miles
north - south by 9 miles east - west.
The major landforms in this irregular-shaped region are
flat-topped, steep-sided, lava-covered highlands of 800 to 2,000
feet elevation between which are belts of rugged hill lands of
only 300 to 600 feet elevation. Many shallow but narrow and
winding valleys run through the hill belts, and numerous side
valleys cut back into the lava uplands. A few higher peaks,
mostly volcanoes, rise above the uplands and reach 3,500 to
4,000 feet. Soils of the valleys and lower slopes are mostly clay
and loam; upland soils have more sand and loose rock.
FIGURE II - 10. Nagasaki, Northwestern Kylish'fi.
Terraced hillsides rise steeply from the waters edge in much
of the Nagasaki area.
Wet-field rice covers most of the narrow valley bottoms. In
many areas wet-field rice also occupies the terraced lower
slopes and small flattish areas in the lava highlands (FIGURE
11 - 10). The rice fields are flooded and are deep in mud from
late June until September, and are wet throughout the year.
Patches of dry-field crops and large areas of woodland and
grass occupy the higher parts of the hill belts and most of the
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higher uplands. The highest and steepest slopes in the uplands
are in scrub forest or are bare.
Wide deployment is almost impossible in the region. Cross-
country movement is possible but difficult in the hill belts,
and very difficult in the highlands.
The 2 chief land passageways within the northern part of
the region lead from Ushizu on the Saga Plain, one westward to
the Sasebo Naval Base on the west coast? the other northwest-
ward to Karatsu port on the north coast. These routes follow
narrow winding valleys in the low (200 to 500 foot) hilly
areas. Deployment and cross-country movement are very diffi-
cult in this low but rugged country.
Low, broken hill country is the dominant type of terrain on
the route southward from Sasebo to Nagasaki. This passage-
way is usee by a railway which, extends along the eastern and
southern sides of Omura.-wan (bay)._Most of the way the rail-
way is built across small coastal flats or through rough, forested,
hill country of cnly 200 to 300 feet elevation. At 2 points the
line crosses high rugged areas of 800 to 1,200 feet elevation.
The first is a 3- to 4-mile section north of Sonogi village on
the northeastern side of the bay. There, 600- to 1,500-foot
ridges reach the sea, and the rail line is carried through. these
by means of deep cuts and short tunnels. The second high
rugged area is immediately northeast of Nagasaki where the
railway crosses a low mountain mass? of 800 to 1,000 feet
elevation, by means of many turns and several tunnels.
The terrain of lki-shima, the Goth-rettO, the Amakusa-jima,
and nearby islands is similar to that of the peninsula. Chief
relief forms are rugged hills of 300 to 800 feet elevation, with
a few high peaks of 1,800 to 2,000 feet. The Amaku.sa-jima
and nearby islands are hilly throughout, but the Got6-retta
and lki-shima have a few small plains 1 to 3 miles in extent.
These plains have some flat areas used for rice fields, but are
otherwise moderately rolling. Upland areas on the islands, like
those on the peninsula, are covered with forest in which are
scattered grassy openings.
C. Relief regions: Shikoku.
Shikoku is located northeast of Kytisha and south of West-
ern Honshu. It is a large island with the long axis extending
northeast - southwest for 138 miles. The island is narrower in
the center than at either end. The western enlarged portion has
a maximum width, north - south, of 95 miles. The eastern
portion has a maximum width, also north - south, of 80
miles. The slender central neck of the island is 35 miles across,
north - south, and extends only 33 miles along the main north-
east southwest axis (PLANT 40).
Shikoku is mountainous throughout with the exception of
a series of narrow plains along the north and northeast coasts
and a group of tiny lowlands around Kechi in the central part
of the south coast. On the 2 northern peninsulas the highlands
are rounded, steep-sided ridges and blocks, oriented in various
directions. In the small northwestern peninsula (between Mat-
suyama arid imabari) a large irregular highland mass reaches
4,000 feet, but on the broader northeastern peninsula only a
few of the scat xired hills and ridges reach 1,600 feet. In con-
trast, the rugged, sharp-sided, folded mountains of central and
southern Shikoku, which are oriented chiefly northeast - south--
west, reach 3,500 to 4,500 feet, and many peaks attain 5,000-
6,000 feet. Long, narrow, deep, winding valleys are aligned
northeast - southwest between the ridges, and in many places
cut through the ridges in almost impassable gorges. Most of
the major valleys are 2,000 feet below the adjacent ridge tops.
In the southwestern peninsula several of these valleys combine
with narrow interior basins to make a series of difficult passage-
ways, -not true corridors, through the mountainous interior
(RourEs 13, and 15 ).-These routes lead across the penin-
sula roughly from east to west. There is no combination of low-
lands leading north - south across the island. The only north -
south railway connecting the northeastern coastal lowland to
the Kr&hi Plain on the south is forced to use several long tun-
nels in order to get through the divides (RouTE 17).
Soils in Shikoku are chiefly clay-loam and clay on the small
plains and coastal valleys, and. clay-loam in the mountain val-
leys of the interior. Upland slopes have thin sand or clay soil,
with much loose rock on the slopes.
Vegetation in the lowlands is dominantly wet-field rice,
with small areas of dry crops on the coastal strips; in the moun-
tain valleys the cultivated lands are mostly .in dry crops, but
with some rice. Most of the upland areas are forested, but ex-
tensive grassy areas appear on the west-- and north-facing slopes
of the southeastern and central highlands, especially north of
KOchi and south of Mishima.
) Southwestern Shikoku Broken Lands.
This rugged highland region includes the southwestern pen,
insula and all adjacent lands southwest of a line from Susaki on
the south coast to the Matsuyama lowland on the northwest
coast.
In this region, sharp-crested, steep-sided ridges with thin,
rocky soils and heavy forests rise 1,000 to 2,000 feet above
narrow winding valleys. Paddy fields occupy the few narrow
coastal flats and the clay loam soils of the larger interior valleys.
Dry-field crops, particularly mulberry .groves, are on lower
slopes.
Deployment is almost impossible in this mountainous region.
Cross-country movement is difficult in the narrow valleys, in
which allowance must be made for deep stream crossings; wet,
muddy rice fields; forests; and high, steep, commanding heights.
Cross-country movement outside the valleys is extremely diffi-
cult, due to the unbroken succession of high, steep, forested
slopes.
There are no good natural land gateways to the region. One
railway enters the northwestern corner by a series of narrow
coastal plains and valleys (ROUTE 20). A highway enters from
the KOchi plain by way of Susaki, but it is forced to cling to
the sides of coastal headlands and valley slopes in many places
( FIGURE II - 111. This region is distinguished from the Central
Shikoku Mountains region chiefly because several combinations
of valleys, coastal sills and interior basins form narrow, deep,
difficult, but nevertheless usable passageways across the south-
western peninsula. The more significant of these passageways,
including those from Shimoda to Sukumo and Shimoda to Ya--
watahama are utilized by ROUTES 3 and 1-4.
(2) Central Shikoku Mountains.
These rugged, forest-covered highlands of 3,500-4,000 feet
elevation, and their sparsely inhabited, deep narrow valleys,
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FIGURE II - II. Central Shikoku.
Typical road in Central Shikoku. This road is on a narrow bench
on a valley side, with steep slopes above and below.
have already been described in the introduction to Shikoku
Island. They are like the Southwestern Shikoku Broken Lands
except that trans-peninsular or trans-regional natural passage-
ways are lacking. Cross-country movement is difficult in the
valleys, due to the swift streams, the forests, and the numerous
commanding heights. In moving across a divide from one
valley system to another a climb of 1,000 to 2,000 feet must
be made over a steep, narrow, timbered ridge. The few roads
over these divides have many deep cuts, high fills, tunnels and
sharp turns (FIGURE II- 12). The lower Naka-gawa (river)
valley provides a short passageway into the region from the
Kii-suido coast on the northeast. Broad, low, easily traversed
gateways do not exist (ROUTE 18). The difficulty of using
existing mountain routes of travel through the Central Shikoku
Mountains is shown on studies of ROUTES 16, 17, and 18
( FIGURES II - 75, 76, and 77).
FIGURE II - 12. Central Shikoku.
Near Yamada, Shikoku. Road and railroad find scant space in
the narrow valleys of Shikoku.
( 3) Kochi Plain.
This lowland is really a series
floored valleys separated by low
lowlands merge along the lower
east of KOchi and reach the sea
central lowland extends 14 niilo
of parallel, cast - west, flat-
but rugged hill ridges. The
Monobe-gawa valley south-
along an 8-mile front. The
P2stward from KOchi to the
FIGURE Ii - 13. KOchi Plain, Shikoku.
The southern coast of Shikoku is mostly steep and rocky. Looking E.
river and then 8 miles southward to the sea. The east - west
part is 2 miles wide, and the north - south part is 4 to 8 miles
wide. Other lowlands, each V? to 1 mile wide and several miles
long, branch from the central plain, chiefly to the east and
west. Where hill ridges reach the sea the coast is rocky (FIG-
URE II- .
The flat valley areas have deep alluvial loam soils, and are
devoted almost entirely to wet rice fields. These fields remain
muddy throughout the year. A few small areas of mulberry
groves and other dry crops occupy slightly raised sand and
gravel areas and lower hill slopes in the northern and western
parts of the region. Deployment and cross-country movement
are possible on the central KOchi Plain and the larger valleys
nearby, but are handicapped by wet rice fields, by farm hamlets
at 3/4-mile intervals, by streams and canals, and by hill.
ridges which form commanding heights of 500 to 1,000 feet
elevation. Cross-country movement is very difficult across the
hill ridges, and over the forested higher mountain ridges to the
north.
There are no natural gateways. A highway follows the coast
eastward and westward from the region, but is forced to use
many sharp turns and deep cuts. A railway tunnels and cuts
through the ridge to the north of Kochi in a series of S-curves
(FIGURE - 12).
(4) Eastern Shikoku Plain.
The heart of this region is a long, narrow, wedge-shaped low-
land, 46 by 4 miles, drained by the deep, east-flowing Yoshino-
gawa (river). The remainder of the region is a 14-mile strip
of coastal flats and hill land which extends south along the
Kii-suido coast. This extension is only 1 to 2 miles wide.
Major landforms in the lowland are flat-topped terraces along
the north side of the Yoshino basin, and low deltaic flats in the
coastal section. Along the Yoshino-gawa is a low 1/4 to 1/2 mile
wide belt of coarse sand and gravel which is subject to flood,
and is left in wild grass. The delta areas along the coast, and the
terrace flats in the Yoshino basin are cropped intensively. Most
of the crop area is in wet rice fields, although mulberry groves
and areas of other dry crops are scattered throughout the low-
land. The steep, 800- to 1,800-foot uplands which surround the
narrow lowland are forested.
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Deployment would be localized on the various delta and
terrace fragments. Cross-country movement would be possible
throughout the lowland, but is handicapped by the wet rice
fields, steep slopes along terrace margins, the meandering
stream channels, and the forested commanding heights. There
are no natural gateways to the region, but the south coast high-
ay enters the coastal strip, and 2 railways, one at either end,
cross the high ridge which forms the region's northern borde.
( RourEs 17 and 19). All of these routes use hairpin turns,
fills, cuts, and, in the case of the railways, tunnels in order to
maintain usable grades through the uplands.
(5) Northern Shikoku. Lowlands.
These lowlands rim the north coast of Shikoku for I 30 miles
but extend inland only 2 to 8 miles. Exceptions are the Nyii-
gawa anci Matsuyama plains on the northwestern peninsula,
which extend inland 6 and 10 miles respectively (FIGURE
ii - 14). Rounded and flat-topped forested hills rise out of the
8-mile wide plain on the northeastern peninsula. Elsewhere
there are fiat plain surfaces and flat-topped terrace remnants
near the highland margins. All of these are intensively cropped..
Wet rice Fields dominate, although patches of dry crops are near
the numerous villages, and mulberry groves and orchards oc-
cupy some of the lower hill slopes (FIGURE II - 15).
Thictitill, 11- 14. Matsuyama Valley, Northern Shikoku.
The extzmsive terracing near Matsuyama reflects the overcrowding
of the small:. Pits of level land suitable for crops. Commanding
Feights are available almost everywhere along the routes
of Southwest japan.
FIGURE II - [5. Northern Shikoku.
Small patches of lowland are backed by steep slopes in many parts
Of Northern Shikoku. Forest plantings can be seen fringing
much of the dry-crop area. About 1925.
Soils are chiefly clay and clay loam, with sandy dune areas
along the beaches. Upland soils are thin, with much sand and
some loose rock. Upper hill slopes and the highland margin to
the south are forested. These uplands rise 1,500 to 3,500 feet
above the coastal plains.
Local deployment in various segments of the lowland is pos-
sible but is handicapped by wet rice fields, numerous streams,
canals, villages, and possibilities of enemy fire from command-
ing hills or marginal ridges. Cross-country movement is fairly
easy if the hills are avoided but it suffers the same general
handicaps as deployment.
Good natural gateways to the region are lacking. The va-
rious rail and highway routes which enter the region from the
interior of Shikoku must use sharp turns, tills, and deep cuts,
in order to cross the unbroken ridges which limit the region on
the south (ROUTES 14, 17, and 20). The railways employ
numerous tunnels.
D. Relief regions: West Central Honshih
West Central Honshu is a rough quadrilateral extending
nearly 200 miles northeast - southwest and 100 miles north-
west - southeast. It includes that part of Central Honshu west
of 138"E (FIGURE II- 107). The western boundary extends
northward through Kii-suido (channel) and Osaka-wan (bay)
to Kebe city, and then northeastward past Biwa-ko (lake) to
the head of Tsuruga-wan (hay) on the north coast. The
northern boundary is fixed arbitrarily at 36'N. On the south,
the area fronts on various arms and embayments of the Pacific
Ocean. Centrally located in West Central Honshu are the
Osaka and Nagoya Lowlands which together comprise one of
the two critical areas of Southwest Japan.
Relief features of West Central Honshu are diverse in type
and irregular in form and distribution (PLANS 38 and 40).
Deployment is possible in the interior basins, and on 1 narrow
coastal plain, but no broad corridors connect these lowlands.
Movement is limited to a series of relatively small separate
compartments and narrow passageways. Cross-country move-
ment is easy on the lowlands and in the larger valleys when
the rice fields are relatively dry and firm (October to May), but
is difficult on the upland areas at all times.
Rugged hills and mountains form a barrier of varying
effectiveness across the north side of the region. These high-
lands increase in height and width toward the northeast. They
vary from 2,500 feet elevation and a width of 12 miles, north
of Biwa-ko (lake), to 9,000 feet elevation and a width of 75
miles near the eastern boundary (138?E). Equally rugged but
less elevated highlands dominate the Kii-hanto (peninsula)
on the south, or Pacific face, of West Central Honshu. This
southern highland does not extend across the area but is cut
off on the east by Ise-wan (bay), and on the west by the Kii-
suidei - Osaka-wan waterway. Between the Kii-hantei (penin-
sula) and the northern uplands is a series of small lowlands
separated by low but steep-sided ridges and blocks. These low-
lands and highlands extend across the area from Osaka Plain
on the west to the Nagoya and Hamamatsu Plains on the east.
One interior basin is almost completely occupied by Biwa-ko
(lake); the others have a few wet areas or smaller lakes. All
have several levels of terraces, and have loam and sandy soils
which are intensively cultivated except on parts of the higher,
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rougher terraces. Wet rice fields predominate but dry crops are
also important, especially on parts of the higher and more dis-
sected terraces. Rougher lands or terraces, together with the
rocky ridges which separate the lowlands, are covered with for-
est, much of it small second growth. Denser forests of larger
trees cover the Kii-hantO (peninsula) uplands and most of the
highlands along the northern border of the region.
(I) Kii-hantO Mountain Land.
The Kii-hantO (peninsula) is a large triangular region of
rugged highlands. The region extends 105 miles east - west,
along the northern, or base, edge of the triangle, and 60 miles
south from that base to the triangle point at Shiono-misaki
(cape). The peninsula forms a seaward barrier between any
invading force and the highly developed, densely populated
basins between Osaka-wan (bay) and Biwa-ko (lake)
( PLAN 40).
The Kii-hantO (peninsula) mountains are of moderate eleva-
tion but have steep sides and narrow winding valleys. Average
peaks near the coast are 1,500-1,800 feet high. Heights increase
inland and reach 5,000-6,000 feet in the west central section
(PLAN 38). Almost all mountain slopes are greater than 30`,/,-'
from the horizontal. There are a few pockets of nearly level
land along the coast and in the larger valleys. Wet rice fields
and dry crops occupy most of the flat or nearly flat areas in
these small lowlands.
The only extensive areas of level or nearly level land in the
Kii-hantO Mountain Land region are at the eastern and western
ends of the northern boundary. The northeastern lowland faces
Enshii-nada (sea). There the uplands give way to scattered
hill ranges of less than 1,000 feet elevation. Within this hilly
area the valleys are 1/2 to 3,4 mile wide and are nearly level.
None of these valleys cuts entirely across the upland, but a
narrow level coastal route winds around the eastern headlands
at Toba ( ROUTE 28). Secondary roads cross to Uji-Yamada
village by means of narrow tributary valleys which lead to low
passes at 800 to 1,000 feet elevation (RouTE 28).
The northwestern lowland consists chiefly of the Kino-kawa
(river) basin. It is a long narrow cleft between the main Kii-
sammyaku (mountains) on the south and the boundary
(Izumi) range on the north. The lowland is 5 miles wide on
the Kii-suidO coast at Wakayama city, but narrows rapidly to
11/2 miles at Kokawa, 16 miles inland. This width diminishes
upstream (eastward), and the lowland becomes a narrow valley
1/2 to 1 mile wide. At GojO, 33 miles inland, 2 narrow
passageways lead northward through the Izumi Range to Gose
and Takatori in the southern part of the Nara Basin (RouTE
30). Passes on these routes are only 500 to 600 feet above sea
level, but commanding heights rise 2,000 to 2,500 feet on
either side. Similar heights rise 1,200 to 1,500 feet above the
wider section of the Kino valley below Kokawa. Most of the
wide part of the lowland is made up of a series of flat terraces
less than 1/2 mile wide and cut into small lA to 11/2 mile blocks
by streams from the mountains. Deep loamy soils cover most
of the terraces. Wet rice fields occupy the flatter blocks near the
streams; dry crops and farmsteads crowd against the slopes on
either side. A sandy, barren, frequently flooded strip parallels
the banks of the Kino.
Vegetation on the Kii-hanto Mountains is a dense forest of
FIGURE II - 16. West Central flonsh
Cable car road to Hiei-san, near Kyoto. Patchy forest and grass
are found on the rugged slopes of the mountains
surrounding the Kinki Basins.
needleleaf and broadleaf trees. Much timber is cut from these
forests.
(2) Kinki Region Lowlands and Highlands.
The Kinki Lowlands and Highlands lie north of the Kii-
hantO and extend eastward from Osaka-wan (bay) to include
the Kasagi Highlands and Suzuka-sammyaku (mountains)
southeast of Biwa-ko (lake) (PLAN 38). Dominant land-
forms within the region are 4 large, flat-floored basins sepa-
rated by low, but steep-sided, hard rock ridges, and overtopped
on the east by the Kasagi Highlands and Suzuka-sammyaku.
Numerous low, narrow passageways which cut through the va-
rious highlands connect the basins with each other and with the
surrounding regions.
The Kinki Lowlands, together with the Nagoya Plain on the
east, contain 4 of the 6 great cities of japan: Kobe, Osaka,
KyOto and Nagoya. The Nara and KyOto Basins are 2 of
the fountain heads of Japanese history and culture.
The highlands of Kinki are of moderate elevation and have
rounded or flattish tops, steep slopes, and deep, well-developed
valleys. On the east, overlooking the Ise-wan (bay) lowlands,
the Suzuka-sammyaku (mountains) have an average elevation
of 2,000 to 3,000 feet (FIGURE II - 16). A few peaks reach
4,000 feet. Ridge tops are rounded, and slopes are steep; a thin
rocky soil, with sparse forests, covers the surface. Farther west
(south of Biwa-ko) the Kasagi Highlands are lower, 1,500 to
2,800 feet, and have flatter tops, but they have similarly steep
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slopes and thin soil with a sparse _forest cover. Passageways
through the Suzuka and Kasagi Highlands form the eastern
gateways to the Khaki Basins and are discussed in connection
with those low lands. The ridges and blocks which lie between
the Kink:. Basins are the lowest in the region, 1,200 to 2,500
feet. They are not easily surmounted, however, because side
Slopes are steep.. These ridges, like the highlands farther east,
have a thin soil, a sparse forest cover arid rounded tops.
(n) Osaka Plain. The Osaka Plain is a large horseshoe-
shaped lowland at the head of Osaka-wan (bay). The prongs
of the horseshee extend southwestward around the bay, and the
rounded toe of the shoe is drawn out northeastward almost to
a point. The plain measures 35 miles southwest - northeast
along the northern arm and 43 miles along the southern arm.
Maximum width is 24 miles, northwest - southeast, at the head
of the bay.
The Osaka Plain has 3 levels. The first is a narrow, 1 to 11/2
mile wide belt of recent alluvium along the shore. This belt is
particularly well-developed along the north shore, west of
Osaka city. Most of this strip is planted with garden vegetables
in dry fields. The second level is 35 to 60 feet above the first
and extends back over most of the lowland. This level is de-
voted largely to wet-field rice. The third level is an old terrace
which has beer. dissected, and now consists of a series of flat-
topped d irt hills which rise 80 to 120 feet above the second
level, Valleys within this hilly belt are cut down 40 to 60 feet
and seriously ir.terfere with _movement from one flat ridge top
to another. Wet rice fields occupy the valleys between the
ridges, and dry-field crops occupy many of the flat ridge tops.
Hill slopes are in second growth timber or grass.
Deployment is easy on the flat first and second levels, but
is restricted on the third, or hilly level. Cross-country movement
is fairly easy on the first 2 levels, from late September to
May, when the rice fields are not flooded or soaked. Other bar-
riers to easy cross-country movement are the urban centers, the
numerous farm villages, averaging -'),4 mile apart, and the
major streams and irrigation canals. Cross-country movement
in the hilly borderland is greatly handicapped by the strips of
wet rice fields in the valleys, and by steep, forested slopes.
Movement along the valley roads between the hills is made
difficult due to wooded commanding heights on either side.
Chief gateways of the Osaka Plain are: westward along the
bay shore to Kobe, northwestward to Ikeda, northeastward
along the Yodo-gawa (river) to the KyOto Basin, eastward
through the Yamato-gawa (river) valley to the Nara Basin,
and southward along the bay shore to Wakayama. Some of
these passageways are utilized by closely parallel routes. Such
alternate ways are discussed along with the main routes.
The coastal route westward from Kobe- to Akashi is a narrow
flat strip, a few hundred feet wide, at the foot of low hill spurs
(R.ouTE :33). The hills rise 200 to 700 feet above the coastal
strip. This 7-mile passageway is used by a Japanese standard
gauge (3'6") railway, a small "special" railway, and a highway.
Houses and small urban units occupy any additional flat space
and fill the lower parts of small valleys which cut back into the
hills. West of Akashi village the route enters a wide coastal
lowland area which extends as far as Himeji, 2 l miles farther
west.
The route northwestward up the Mu.ko-gawa (river ) gorge
from Ikeda on the northern edge of the plain is even more
restricted than the coastal route west of Kobe. The narrow,
winding gorge of the Muko is only Y8 mile wide at the top
and is cut down 700-800 feet below the adjacent flat-topped
plateau remnants. Sides of the gorge are covered with rock
debris and sparse forest. Only 1 transport line, a railway, uses
the gorge, and it has many turns and one or two tunnels per
mile in the 10-12 mile section below Sanda. North of Sancta
the valley widens to ? mile at the bottom and the railway
uses fewer turns and tunnels.
A second route leads almost due north from Ikeda, and par-
allels the upper part of the Ikeda-Sanda railway route. This
second route uses the shallower, but steeper and equally crooked
valley of the Ina-gawa (river), and is occupied by a highwa.y
only. Forest-clad, rocky slopes rise 200 to 300 feet above this
route. Both of the passageways from Ikeda north into the
Tamba Plateau lack room for deployment and are easily
blocked at many points. Two more highway routes, relatively
steep and crooked, lead northward over the Tamba Plateau from
the northwestern rim of the Osaka Plain. Both lead to the
Kameoka Basin, where they join the main passageway leading
northwestward from Kyoto to the north coast of Honshu.
The only true corridor leading to the Osaka Plain is the
narrow wide gap at the northeastern apex of the plain,
where the Yodo-gawa (river) breaks out of the KyOto Basin
(ROUTE 24). Even here the river and its low, grass-covered
flood plain occupy /.3' of the gap and crowd the 3 railway
lines and 2 highways onto a few-hundred-foot wide strip
along the northern bank and onto an even narrower ledge on
the southern bank. Forest-covered hill spurs rise 400 feet above
the river on the south side and 700 feet on the north side, and
completely dominate the 11/4 mile length of the gap. The
adjacent towns of Hirose and Yamazaki occupy the widest -part
of the flat area on the north side of the corridor. A parallel
railway route crosses the hilly upland 5 miles southwest of the
Yodo-gawa gap and turns southward onto the southern arm of
the KyOto Basin. This upland railway rises only 75-100 feet
to cross the grass- and forest-covered upland, but it has many
cuts and fills and 1 short tunnel at the divide.
The principal eastern gateway to the Osaka Plain is the
Yarnato-gawa gorge through the low, round-topped ridge be-
tween the Osaka Plain and the Nara Basin (ROUTE 30). One
railway and a highway follow this gorge, and rise only 45 feet
in the 8 miles through the ridge. The gorge is narrow and
crooked, however, and the steep rock- and forest-covered slopes
rise 500-600 feet above the valley bottom. In order to avoid
exceedingly sharp turns, the railway tunnels through several.
projecting spurs. Four alternate parallel routes climb across the
ridge south of the Yamato gap. These routes-2 railways and.
2 highways?are all within 5 miles of the river gateway. These
routes climb 300 to 600 feet to low saddles in the ridge, but
have fewer turns and tunnels than the route through the gorge.
On the south a coastal rail route crosses the low western end
of the lzumi Range south of Fuke and reaches Wakayama in
the Kino-kawa lowland of the Kii-hantO (peninsula). The
low, forest-covered range is crossed by means of numerous
turns but no tunnels are needed. The pass is between 400 and
600 feet elevation. An alternate rail route 6 miles to the east
rises only to 35 feet, but uses a 1 mile tunnel under the divide
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and several other short tunnels in maintaining its relatively low
grade. A highway follows this route and rises to 550 feet on the
divide above the tunnel.
(b) Nara Basin. The Nara Basin is an oblong depression
with irregular boundaries. Its maximum dimensions are 16
miles north - south, and 10 miles east - west. It is southeast
of the Osaka Plain, and south of the KyOto Basin.
Like the Osaka Plain, the Nara Basin has 3 levels. The
lowest level is a flat plain of alluvial material 135-165 feet
above sea level. It is the most extensive of the 3 levels and
covers at least 80 per cent of the basin. This large area is almost
flat but is broken here and there by low mounds and isolated
hills which rise 20 to 250 feet above the plain. The second
level, which is 30 to 60 feet above the first, is a narrow irreg-
ular belt of flat terrace fragments lying along the northern
and northeastern sides of the basin. These remnants of old ter-
races are separated by the steep-sided, flat-floored valleys of
numerous headwater streams of the Yamato-gawa. The third
level is a jumbled mass of hills cut out of old stream deposits.
These low but rugged uplands risc 40 to 80 feet above the
second level and reach elevations of 275 to 300 feet.
The highland rim of the Nara Basin is composed of steep-
sided, round-topped ridges and blocks with maximum heights
of 1,500 to 1,800 feet, except on the southwest where a few
peaks reach 3,000 feet. A thin, rocky soil and a sparse forest
growth cover these uplands. Most of the forest is second growth.
The basin floor, especially the broad lower level, has a loamy
surface over a relatively dense subsoil. The carefully tended
soil is occupied almost entirely by wet rice fields, which are
flooded and muddy from May to September. Much of this area
yields a dry crop after the rice is removed. The second level,
or flat-topped terrace remnants, has wet rice fields in the valleys
and dry crops with some rice on the higher flats between
streams. The hilly (third level) areas of the north and west
have rice and dry crops in the larger valleys, and woodland on
the hill slopes.
The flat floor of the Nara Basin is broken by a network of
streams and irrigations ponds, by scattered earth mounds,
and by isolated hills. The flat areas between larger
streams and large ditches average not more than 1 to 11/2
miles across. Small, compact agricultural villages are distrib-
uted evenly over these flats. The average distance between
villages is 1/2 to 3/1 mile.
Large-scale deployment is relatively easy on the flat lower
level, except from early May to September, when the rice fields
are flooded. Local, small-scale deployment is possible on the flat
terrace remnants of the second level, but is difficult in the
valleys between the flat fragments. In the rugged hills of the
third, or highest level, deployment is almost impossible. Cross-
country movement is possible on the flat lower level, but is
handicapped by the muddy fields, scattered mounds and hills,
and the numerous ditches, ponds, and hamlets. The greatest of
these handicaps is the water and deep mud in the wet rice fields,
from May to September.
Principal natural passageways which connect the Nara Basin
with other lowlands are: southward through the Izumi Range
to the Upper Kino-kawa (river), westward along the Yamato-
gawa to Osaka, northward through the Nara Hills to Kyoto.
and eastward up the Hatsuse valley and on past Ueno to the
Ise-wan Lowlands.
The 2 parallel southern routes through the Izumi Range to
Gojo on the upper Kino-kawa (river), and the western route
to the Osaka Plain have been discussed in connection with the
Kii-hanti5 (peninsula) and the Osaka Plain (ROUTE 30).
The northern routes between the Nara Basin and the south-
ern or Kizu-gawa (river) arm of the KyOto Basin cut through
a 2-mile wide belt of low hills (RouTE 31). These hills are a
segment of the third or highest level of the basin deposits.
Two railways and 2 highways are carried through this rugged
area by means of cuts and fills. Roadbed levels rise only a few
feet in making the passage. Nevertheless the hills are a con-
siderable handicap to movement because they are irregular,
have steep sides, and rise 60 to 150 feet above the roadbeds.
The eastern gateway of the Nara Basin follows the Hatsuse-
gawa (river) from Sakurai in the southeastern part of the
lowland. The route turns northeastward near Haibara, and,
after crossing a low divide, enters a shallow basin and joins
the east - west Kizu-gawa passageway at Ueno (ROUTE 26).
The route is used by a railway and a highway, both of which
have only moderate grades and turns except at the divide west
of Haibara. There both rail and road have several sharp turns
and the railway has several tunnels. Commanding heights rise
1,200 to 1,500 feet above the roadbeds at many points.
Deployment is either impossible or very difficult within any
of the gateways of the Nara Basin, and cross-country movement
in the low, but rugged uplands along these routes is also
difficult.
(c) KyOto Basin. The Kyoto Basin proper is an oblong-
shaped depression 14 miles north - south by 5 miles east -
west. A narrower arm, the Kizu-gawa (river) corridor, extends
miles southward from the southeastern corner of the region
to the Nara Hills at the northern end of the Nara Basin. This
corridor is only 11/2 to 2 miles wide (ROUTE 31). A smaller
lowland, the .Daigo pocket, projects northeastward 5 miles
from the eastern side of the basin toward the southern tip of
the Biwa Basin, but is separated from that lowland by a narrow
rock ridge. A smaller, lower ridge separates the Daigo pocket
from the eastern outskirts of Kyoto city.
Landforms of the Kyoto Basin are much like those of the
Nara Basin; therefore only outstanding differences will be dis-
cussed in detail. The Kyoto Basin has the same 3 levels: a
broad young alluvial floor, surrounded by fragments of low
flat-topped terraces, which are backed in turn by a wider belt
of rugged dirt hills. Hard rock ridges and low mountains rise
above the hill belts and form the rim of the basin (FIGURE
II - 17 ) . Average elevations in the 3 basin levels and of the
highland rim are successively: 60 feet, 95 feet, 260 feet, and
1,600 feet.
The broad lower level is covered with wet rice fields; and the
second or fiat terrace level is occupied by dry crops and some
rice. Tea bushes, 3-5 feet high, comprise much of the dry-crop
area (FIGURE ii - 18). As in the Nara Basin, the dirt hills and
highland rim are covered with thin forests. Soils on the broad
lower level are chiefly loam. On the flat terraces and hill levels
clay, sand, and gravel predominate (FIGURE II - l 9).
The nearly level surface of the broad low first level of the
basin favors deployment and cross-country movement, but
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Ficaria: 11- 17. Khaki Region. livm- Central Honshu.
'NonTern KyOto Basin from Hiei-san, looking SW. The northern
part of the KyOto Basin is invaded by low, but steep outliers
of the surrounding mountains. Part of the city of
KyOto is in the background. Prior to 1933.
FiGuRE B - 18. Kinki Region, West Central Honshu.
1.'m bushes on the Hat surface of a low terrace in the east
central KyOto Basin. Looking NE, 1933.
these are handicapped by flooded and muddy rice fields, from
May to '.ate September, also by numerous streams and villages,
and by I large, shallow, swamp-bordered lake, Okura-ike, which
is 2 to 2 [A miles in diameter. Okura-ike is located in the east
central parr of the Kv-Oro Basin. An additional large barrier is
KyOto city which occupies almost the entire northwestern end
ot the basin ( FIGURE Ii - 20). On the intermediate terrace
level, deployment and cross-country movement are relatively
easy on the flat surfaces, but are greatly handicapped elsewhere
by rice fields in the valleys, and by dense woods and steep
slopes on terrace margins. The long, steep slopes of the hilly
borderland and the highland rim, covered with loose, rocky
soil and sparse forest? are even greater handicaps to military
operations.
Chief natural gateways of the Kyoto Basin are the southern
or Kizu-gawa corridor to the Nara Basin, the southwestern or
Yodo-gawa gap to the Osaka Plain, the northwestern or Ka-
meoka route to the north coast, the northeastern tunnels (a
triari-made route) to the Biwa Basin, and the southeastern or
Kasagi route to Ueno and Ise-wan (bay). '
The Kizu-gawa corridor is a fiat-floored southern extension
of the main Kyoto Basin which connects with the Nara Basin.
across a 2-mile belt of hills as explained in connection with the
Nara Basin (RouTE 31). The Yodo-gawa (river) gateway to
the Kyeito Plain was discussed in connection with the Osaka
Plain (RouTE 24).
FIGURI II - 19. Kinki Region, West Central Honshu.
Terrace bank near Uji, KyOto Basin. Sands and gravels make up
the soil of the terraces which rim parts of the Kinki Basins.
Three-inch hand compass used for scale. 1933.
FIGURE 11 - 20. Kinki Region, West Central HonshR.
Kyoto city from Hiei-san. Looking SW. KyOto city lies on the
flat floor and lower hill slopes of the northern
KyOto Basin. Prior to 1933.
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The northwestern outlet of the Kyoto Basin penetrates the
broken Tamba Plateau and eventually reaches the north coast
at Maizuru (ROUTE 32). Most of the route is along narrow
winding valleys 800 to 1,400 feet below the rugged plateau
remnants. The most difficult stretch is the 61/2-mile gorge of
the Katsura-gawa, west of KyOto city. Here the gorge is so
narrow and winding that the single railway which follows the
route is carried through by means of notch-like cuts in the
steep side slopes and by tunnels through projecting hill spurs.
The upland slopes are forested along most of the route, but
north-facing slopes near the Japan Sea are in grass. Wet rice
fields and some dry crops occupy the floors of wider valleys
including the 2-mile wide Kameoka Basin.
No natural corridor connects the Kyoto Basin and the Biwa
Basin. They are separated by a steep-sided, forest-clad ridge
which blocks the head of the tributary Daigo pocket east of
KyOto. This ridge is 2 miles wide at its narrowest point and is
1,000 to 1,500 feet in elevation. The Seta-gawa, which drains
Biwa-ko cuts across the ridge by an indirect, 13-mile long
route, and its canyon is so deep, 800-1,100 feet, and has such
steep sides that only parts of it are followed by a road. The
central part of this road between the basins climbs out of the
canyon and follows the ridge top and several small tributary
valleys. An additional handicap of the Seta-gawa route is the
swampy nature of the soil where the river enters the Kyoto
Basin at Uji. Most of the traffic between the Kyego and Biwa
Basins moves directly east from Kyoto city across the 2
forest-clad ridges on either side of the Daigo pocket, and
reaches Biwa-ko at Otsu (ROUTE 24). One railway, 1 high-
way, and 2 aqueducts from Biwa-ko follow this route. In order
to surmount the ridges, which are 1 [,/2 to 2 miles wide and 500
to 800 feet high, the highway has many sharp turns and 1
short tunnel. The railway and aqueducts have straighter courses
but use tunnels as much as 11/2 miles in length. Deployment
and cross-country movement would be very difficult on the
ridges but fairly easy in the Daigo pocket.
The only natural passageway eastward from the Kyoto
Basin follows the upper Kizu-gawa valley after it turns east-
ward at the southern end of the KyOto Basin. The passageway
continues eastward through a series of valleys and basins to
Kamcyama in the Ise-wan Lowlands (ROUTES 25 and 27)
Most of the valleys followed by this 40-mile long route are
1,000 to 1,200 feet below the adjacent uplands, and are less
than 1/2 mile wide. The Ueno Basin is wider, 11/7 to 21/2 miles,
but extends only 6 miles along the route. Wet rice fields oc-
cupy the floor of this basin and most of the level spots in the
narrow valleys. Other parts of valley floors and adjacent up-
lands are in forest. Deployment would be possible along this
route only in the Ueno Basin and smaller basins along the
upper Kizu-gawa. Cross-country movement along the passage-
way would be moderately difficult, and movement on the adja-
cent rugged uplands would be very difficult.
(d) Biwa Basin. This large basin extends northeast from
the latitude of Kyoto city to within 10 miles of Tsuruga-wan
(bay) on the north coast. The Biwa Basin has the shape of a
wedge with its base to the south. It is 39 miles long northeast -
southwest, 26 miles wide east - west at the base, and 15 miles
wide east - west near the apex (north). The western and
northern parts of the basin are occupied by Biwa-ko. This
leaves a 17- by 33-mile triangle of lowland southeast and east
of the lake. In addition there are small scattered bits of gently
sloping land along the western and northern shores of the lake.
On the western side of Biwa-ko these scattered lowlands are
small deltas which extend out 1 to 2 miles into the lake and
are 2 to 5 miles broad. Small sections of the deltas are in wet
rice fields; the remaining surface is forested. These small low-
lands are separated by rocky spurs from the Tamba Upland
to the northwest. The spurs rise 500 to 1,500 feet above the
deltas. Farther inland are forest-clad ridges which rise an addi-
tional 1,500 to 2,000 feet. Deployment and cross-country
movement are possible on the separate deltas, but such opera
tions are extremely difficult on the steep, rock-covered ridges
between the deltas.
East of Biwa-ko an almost solid fringe of deltaic material
slopes up gently from the shore. One to 2 miles inland the
slopes give way to broad terraces at levels 40 to 50 feet high.
The terraces in turn rise even more gently to meet and pene-
trate between the earth hills and low rocky ridges which form
the highland border to the south and east. The hills and ridges
rise 900 to 1,200 feet above the flat terraces. Spurs and isolated
ridges and hills extend westward into the lowland and reach
the lake shore at several points. Between these upland spurs
long streamers of flattish lowland reach back 10 to 15 miles
from the lake shore. Near the lake the ridges and hills are
discontinuous and the lowland areas are connected north - south
by numerous flat strips.
The terraces are dissected little by streams from the high-
lands. On the deltas the major streams have built up their beds
until they form elevated barriers 20 feet or more above the
delta level. In places roads and railroads tunnel under the
rivers.
The deltas and lower terraces have mixed loam and clay
soils devoted almost entirely to wet rice fields. The rugged
earth hills have much sand and gravel mixed with finer soil
material. The higher uplands which surround the basin have
a thin. sandy, rocky soil. Forests on these uplands and the hilly
lands in the basin have been thinned by repeated cutting; as a
result, the soil has been deenly eroded on many slopes.
Chief gateways of the Biwa Basin are: southwestward from
Otsu to the Kyoto Basin. northward from Kinomoto village to
Tsuruga on the north coast. eastward through the Sekigahara
gap to the Nagoya Plain, and southeastward to Higashitsuge
on the Ueno-Kameya ma route to Ise-wan (bay).
The southwestern outlet to the Kyoto Bisin his been dis
cussed in connection with that area (RouTE 24). On the north
a railway and a highway follow separate deco, narrow, winding
valleys from Kinornoto to the north coast of Honshu at
Tsuruga (RouTE 23). A second highway follows similar nar-
row valleys northward from Imazu, west of the like, and joins
the first 2 routes near Tsuruga. The total road distance on
each of these routes is 14-15 miles. All 3 routes have many
sharp turns, and the railway has several ninnels. One railway
tunnel, under the divide, is nearly a mile long. Steen. forested
slopes rise 1,000 to 2,000 feet above the narrow valleys and
provide numerous commanding heights and potential road
blocks on all 3 routes.
The eastern gateway of the Biwa Basin is the Sekigahara
gap, in the Suzuka-sammyaku (mountains); this gap leads to
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the Nagoya Plain (RouTEs 23 and 24). The main route
through the gateway varies from I/2 to 2 miles wide throughout
14 miles of its length, but shrinks to a few hundred feet in the
3-mile section at the divide. This route has a railway and high-
way. Both rise less than 500 feet to the pass, where the railway
uses a short tunnel. Fields of wet rice and dry crops (mostly
mulberry groves) occupy the broader flat areas along the
route. Forest covers the ridges and spurs, which rise 800 to 1,000
feet above the roadbeds. A second route, occupied by a high-
way, follows the same general course and crosses the main
route from southeast to northwest. This second route is similar
to the first, except that almost half of its length is through
narrow, relatively steep valleys with abrupt, forested, side
slopes. The routes cross in the small, 1 by 11/4 mile, Sekiga-
hara basin, the key section of the Sekigabara gap.
On the southeast, 2 parallel routes follow branches of the
Yokota-gavva (river) above Ishibe village and cross a low divide
to join the west - east Tien? basin-Kameyama passageway
( Rptirt 25). These routes are in broad fiat-bottomed valleys
until they reach the divide north of the Ueno-Kameyama route
where narrow, winding, steep-sided valleys arc used. The west-
ernmost of these 2 routes has only 4 miles of these narrow
valleys, but the easternmost route has nearly 9 miles of such
constricted t-xissage. Slopes above the valleys rise 600 to 1,000
feet and are heavily forested. Wet rice fields occupy the larger
lower valleys; the higher narrow valleys are forested.
The tleno-Kameyama passageway through the Suzuka-sam-
rnyaku (mountains) has been described in connection with the
Kyoto Basin (RouTEs 25 and 27).
(3) Ise-wan Lowlands.
The Ise-wan (bay) region is a large? horseshoe-shaped low-
land which curves around the western, northern and eastern
sides of the bay. The bay and lowland form an eastern approach
to the strategic Kinki Basins (Biwa, KyOto, Nara, Osaka). The
western arm of the Ise Lowlands extends 48 miles southward
along the bay and is 9 to 11 miles wide. The eastern arm of
lowland extends 24: miles southward from Nagoya, at the
head of the bay, to the north shore of Atsumi-wan, a small
tributary bay. This eastern arm is irregular in shape, as it in-
cludes a large bay and peninsula (Chita-wan and Chita-hanto).
The arm varies from 8 to 20 miles in width. North of the bay
is the Nagoya Plain which is 32 miles long north - south and
has an average east - west width of 24 miles. The inland mar-
gins of the plain are not sharp. Arms of low flattish land ex-
tend back 6 to 15 miles into the surrounding mountains along
the lower courses of the major streams (FIGuRE TI - 21).
The Ise-wan Lowlands have several levels similar to those
in the Kinki Basins. Along the bay shore there are low, flat
lands less than 25 feet above sea level. These extend back 2
to 5 miles from the western and eastern shores of the bay
and 15 to 20 miles from the northern or Nagoya shore. Inland
from these low deltas are older higher sediments rising 50 or
60 feet above sea level. A gentle, continuous, smooth slope
connects the 2 levels. The higher flat lands are 5 to 10 miles
wide. They are bordered inland by highly dissected terrace rem-
nants which form hilly areas 100 to 200 feet above the flat
lowlands. These steep-sided dirt hills give way in turn to the
hard-rock ridges and spurs of the surrounding highlands. These
rise sharply 500 to 2,500 feet above the hilly areas. A few high
peaks near the margin of the Ise Lowlands reach 3,500 to 3,800
feet.
Rugged hilly land is almost continuous back of the deltas
along the western arm of the lowland, south of -Kuwana.
This hill belt is 2 to 8 miles wide and merges into the western
highland rim. Only a few scattered hilly areas lie against the
northern upland rim. A 3- to tO-mile wide hilly zone borders
the eastern side of the Nagoya Plain, however, and extends
southwestward to cut the coastal delta lowland in two and form
the Chita-hanto (peninsula ) . This low but rugged hill barrier
separates the small Okazaki Plain from the Nagoya Plain.
FIGURE 11 - 21. Ise-wan Lowlands. West Cental flon.rh'R.
Seki village. Level, rice-covered alluvial bottom land; lower slopes
in dry crops; middle and higher slopes in forest; an elongated
village, innumerable telephone, telegraph, and electric
lines?a typical Japanese basin or valley
landscape. 1931.
Only 1 ridge from the surroundings highlands reaches far
out into the plain. This highland block extends southeastward
from the Sekigahara passageway and reaches the upper end of
the Kiso-gawa delta above Kuwana. Dissected terrace foot-
hills which surround the ridge reach to within 2 miles of the
bay shore at Kuwana.
Soils of the lowland flats are mostly loam, with sand and
.much clay along the river channels. Hilly areas have sandy and
gravelly soils mixed with clay, and higher uplands are covered
with loose, rocky, sandy soils.
Vegetation on the low -flat plains and river bottoms is
chiefly wet-field rice. Higher parts of the flat land and less
steep slopes in the hill lands are in dry crops. Mulberry groves
dominate these dry-crop areas west of the bay and north and
east of Nagoya. Many orchards are on the flat areas east of
Nagoya. Forests cover the steeply sloping land in the hills and
highland rim.
Deployment is possible on the flat lowlands, including the
larger valleys, but is handicapped by deep mud in the rice fields,
and by the numerous streams, canals, and farm villages. Cross-
country movement is also relatively easy on the broad flat
lowlands, but it meets the same handicaps that affect deploy-
ment. The hill belts have few flat areas, but there are many
narrow valleys interconnected by low saddles. As a result, de-
ployment and cross-country movement are greatly restricted in
these areas. In the rugged highland rim of the region both de-
ployment and cross-country movement are very difficult.
Chief gateways of the Nagoya Plain are the coastal route
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to the eastern end of the Kii-hanto (peninsula) on the south;
the Kameyama and Sekigahara passageways to the Kinki
Basins on the west; and 3 routes to Toyohashi and Hamamatsu
on the southeast. The passageways to the Kii-hanto (penin-
sula) and the Kinki Basins have been discussed in connection
with the Kii and Kinki regions (ROUTES 23, 24, 25, 26, 27,
28, and 30). The railway routes through the high mountains
to the northeast are not natural passageways but are long and
extremely difficult man-made ways along a series of deep, wind-
ing, forested valleys. These routes are not discussed here, be-
cause a large part of each way lies north of 36?N, the northern
limit of this study.
At the southeastern tip of the Nagoya Lowlands 3 routes
cut through the narrow belt of highlands south of Okazaki
and reach Toyohashi in the Hamamatsu-Toyohashi coastal re-
gion. Two of these routes lie inland, the third follows the coast.
The 2 inland routes follow a series of narrow but fairly straight
valleys. The easternmost of these 2 inland routes is the old
TokaidO Road (FIGURE II - 22), now replaced in this section
by a new highway and a light railway (RouTE 22). This route,
the highest of the 3, rises only 330 feet in crossing the upland.
The western inland route, a railway, follows the coast from
Toyohashi city to Gamagori, and then turns north and crosses
the upland with a climb of only 135 feet. A short tunnel car-
ries the road through a small ridge east of Gamagori. The outer
or coastal route, also a railway, follows the shore of Atsumi-
wan (bay) to Ishiki and there turns northward around the
western end of the highland. This route passes through a 24.
milesection of rugged coastal highland east of Ishiki. Corre-
spondingly difficult sections on the other 2 routes are 4 miles
of narrow valleys along the GamagOri railway and 26 miles of
rugged country along the eastern or TOkaido route. Command-
ing heights rise 350 to 850 feet above the narrow sections of
all 3 routes.
FIGURE II - 22. Ise-wan Lowlands, West Central Honshu.
A view of the old Thkaida Road in the vicinity of Nagoya. Trails
somewhat similar to this are found throughout
Southwest japan. 1931.
Wet rice fields cover the floors of all but the narrowest val-
leys. Groves of mulberry and other dry-field crops occupy parts
of lower slopes above the routes. Higher slopes and summits are
forested. Cross-country movement along or parallel to these
routes is made difficult by rugged terrain, forests, wet rice fields,
and many small villages. Deployment is possible only in the
broader northern sections of the central and western (railway)
routes, and is handicapped there by rice fields, streams, and
villages.
(4) Hamamatsu-Toyohashi Coastal Lowland.
This narrow coastal region extends eastward from the mouth
of Ise-wan (bay) past the eastern boundary of the area covered
in this study (138?E). A more detailed study of the entire
region is given in JANIS 85, which covers Central and
Northern Honshu. Only a brief discussion is given here, and
this is limited to the 54-mile long section lying between Ise-
wan and 138?E. This western section is 8 to 14 miles wide
from the Pacific Ocean beaches northward to the rugged foot-
hills of the Central Honshu Highlands.
Major divisions of the region are the river valley and terrace
lands east of Hamana-ko (lake), the hilly lands of Atsumi-
hanto (peninsula) west of Hamana-ko, and the triangular
Toyohashi coastal plain north of Atsumi-hantii.
East of Hamana-ko the 8- to 10-mile strip between the sea
and the mountains is divided almost equally between low flat
river plains and broad terrace remnants which are in various
stages of dissection. Along the coast there are good beaches
backed by lines of sand dunes, 20 to 40 feet high, and several
parallel sand ridges 6 to 10 feet high. Narrow, 1- to 3-mile
wide strips of flat sandy coastal plain lie between these low
ridges and the outer edges of the terraces. These narrow coastal
flats form low east - west corridors between the river plains,
and make possible a continuous east - west lowland route as
far west as Hamana-ko. The 2 flat river plains, Tenryii and
Ota, are respectively 27 miles and 10 miles wide cast - west,
and each extends back 6 to 8 miles from the outer tips of the
terraces. The terraces, which lie between the river plains are
40 to 50 feet high at their outer, or southern, ends, and rise
inland in a series of benches and gentle slopes until they reach
300 to 350 feet at their junction with the foothills. The terrace
surfaces are broken into segments by many long, narrow,
north - south valleys, the floors of which lie 40-100 feet below
the original terrace levels. The flat-topped segments between
the valleys are generally less than 1 by 2 miles wide but on the
large terrace north of Hamamatsu some flat areas measure 21/2
miles.
Soils of the river basins are mostly loam and sand. On the
terraces, the small valleys have sand and loam with some
gravel; the terrace flats are chiefly a fine volcanic ash material
overlying sands and gravels. The large terrace flats north of
Hamamatsu have a compact clay surface soil that is difficult to
break with hand tools even after a heavy rain.
Vegetation east of Hamana-ko (lake) is grass and scrub
pine on the beach dunes and ridges, wet-field rice and some dry
crops in the river plains and coastal flats, and dry crops (chiefly
tea) and thin forest on the terraces. In the Tenryii-gawa (river)
plains most of the dry crops are on small raised sand and gravel
mounds 2 to feet above the surrounding wet rice fields.
Rugged uplands which bound the region on the north have a
cover of thin forest with many grassy openings.
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West of Hamana-ko (lake), rugged hills 200 to 1,000 feet
high are scattered throughout the _Atsumi-ha.nto ( peninsula).
A narrow 1/1 mile belt of sand dunes and sand flats extends
along the north and south coasts and widens to 1 mile on the
west, at the mouth of Ise-wan. Hill spurs break through to the
coast and .Form rocky headlands at a few places. Narrow valleys
and wider pockets of lowland extend inland between the hills
and cross the peninsula in several places. A similar lowland belt
cuts across the base of the peninsula at Futagawa and provides
a narrow but easy passageway between the mouth of Hamana-
ko and the Toyohashi plain (RouTE 22).
Soils and vegetation on Atsumi-hanto (peninsula) are sim-
ilar to those described above. One difference is that on the
peninsula most of the dry-crop area, on .fiats and lower slopes,
is in mulberry groves instead of tea bush.
The small triangular Toyohashi plain north of Atsumi-hanto
(peninsula) forms a flat amphitheater, 7 by 9 miles, at the head
of Atsumi-wan (bay). The plain is mostly clay-sand material
brought down by the Toyo-kawa (river) and several smaller
streams. Almost all of the lowland is in paddy fields. Along
the Toyo-lcawa (river), in the northeastern section, and south
of Toyohashi city, mulberry and other dry crops occupy much
of the :low flat area and some of the lower hill slopes. Most
of the rugged foothills which rise 600 to 1,000 feet above the
plain are forested, but a few slopes are covered with coarse
grass.
Within the Hamamatsu-Toyohashi region deployment and
cross-country movement are least handicapped on the river
plains of the Ota, Tenryii, and Toyo.. More difficulties are en-
countered in the eroded terraces east of Hamana-ko (lake) and
in the low hilly lands of eastern .Atsumi-hantO ( peninsula).
Most difficult are the steep outer slopes of the terraces and the
high rugged hills on western Atsumi-hanto and along the in-
land border of the region.
On the river plains and coastal flats, including the dune areas,
chief handicaps to mobile operations are sand dunes and ridges
6 to 40 feet high, numerous streams and drainage ditches, many
closely built agricultural hamlets, and almost continuous wet
rice fields which are water-soaked and deep in mud the year
around. In the terrace and low hilly areas alternate flat land
and steep. slopes, with wet rice fields on much of the flat land,
greatly imit deployment and cross-country movement.
In the higher areas, deployment and cross-country movement
are limited, both in area and in direction, by steep slopes, by
loose rock, and by scrub forest.
Critical points which must be passed in moving from the
beaches toward the important Ise-wan Lowlands are: the dune
belts back of the beaches; the narrow 1- to 3-mile coastal flats
between the terraces and the sea, south of Hamamatsu and
Nakaizumi; Hamana-ko (lake), which extends completely
across the lowland; and the 5-mile hill belt between the lake
and the Toyohashi plain.
Only 2 natural passageways form land gateways to the Toyo-
hashi-Hamamatsu region. These are the northwestern routes
through the rugged lands north of 'Toyohashi and the eastern
continuation of the Hamamatsu Lowland beyond 138 'E. The
first of these routes northward from Toyohashi has been dis-
cussed in connection with the Ise-wan Lowlands (Rearrii 22).
The second, or eastern, outlet is outside the limits of this study,
and is treated in JANIS 85.
(5) Central Honshu Rugged Highlands.
The rugged highlands north and east of the Nagoya Plain
are part of the extensive mountains of Central Honshu. Only
about half of this great barrier is within the area of this report;
the highland region as a whole is described in JANIS 85.
Measuring 150 miles north to south and 100 miles west to east,
these high rugged mountains occupy the full width of HonshU
and include its highest mountain ranges. They are the major
obstacle to communication and movement between Southwest
and Central Honshu. General elevations increase from west to
east and from south to north, from about 3,000 feet in the
southwest to about 10,000 feet in the northeast. In the east
are 3 major ranges, oriented from north to south, the Hida-
sammyaku, the Kiso-sammyaku, and the Akaishi-sammyaku,
separated from each other by the Kiso-gawa and the Tenryd-
kawa. The Kiso-sammyaku is the only one of the 3 ranges
which lies largely within the area of this report. Northwest of
the Nagoya Plain a 3,000- to 5,000-foot rugged highland ex-
tends westward from the Hida and joins an extension of the
Suzuka-sammyaku north of Sekigahara pass to complete the
encirclement of the Nagoya Plain on its landward side. The ter-
rain throughout the Central Honshu Rugged Highlands con-
sists almost exclusively of a maze of high, sharp-crested, forested
ridges, of steep slopes, and deep narrow canyon-like valleys.
Settlements have avoided the region, and few roads and rail-
ways penetrate or traverse it.
There are 3 lowland areas within the part of Central Hon-
shu Rugged Highlands included in this report. These are the
Fukui -Plain, the Iida valley and the Nakatsu Basin. The
Fukui Plain is the southern extremity of the coastal lowland
of Kanazawa described in JANIS 85. The Iida valley, on the
upper Tenryii-kawa (river) is about 35 miles long, and 2 to
5 miles wide. It is isolated by mountains, and consists of a string
of disconnected, flat, rice-covered river plains, at best a mile
wide, bordered and separated by undulating higher gravel plains
or by low hill ridges 100 to 300 feet above the river plains.
These transverse hills are most extensive on the western side
of the valley. Below Iida the southward draining Tenryu-kawa
crosses the mountainous terrain in a wild, practically inaccess-
ible gorge. The Nakatsu Basin is on the middle course of the
Kiso-gawa. It has strongly rolling hills, 300 to 600 feet high,
and is separated from rhe Nagoya Plain by even higher hills.
The Kiso-gawa flows along the northern edge of this basin
in a narrow gorge 600 to 1,000 feet deep. Within the basin
the valleys arc shallower and wider, movement is easier, and
some roads and settlements have been established.
The Central Honshu Rugged Highlands are an effective bar-
rier between Southwest japan and TOkyo. Land communica-
tion along Honshu's south coast follows the Hamamatsu-Toyo-
hashi Coastal Lowland, but to the east of the area covered in
this report the mountains reach the Pacific Ocean, and roads
and railroads are forced to use steep slopes or tunnels. On the
north (outside the area under consideration) the mountains
reach the Japan Sea, blocking the coastal routes for a distance
of about 15 miles. No good natural passageways go through
the Central Honshu Mountains entirely. The best route through
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part of the region is via the Iida valley, eastward from which
other basins, separated by hill and mountain ranges, could
conceivably be used in an advance upon Tokyo from the west.
Penetration of the Iida Valley from the west, however, would
be a major undertaking. From Nagoya it would be necessary to
cross the rugged hill country of the lower Kiso-gawa to the
Nakatsu Basin, thence over 2 high passes, 4,000 to 4,300 feet,
in the central part of the Kiso-sammyaku. Mountain roads
from Nakatsu to Iida now follow these routes.
E. Western Honshu.
Western Honshu is the long peninsula that extends west-
ward from the Kinki Basins (Osaka, Kyoto, Biwa) to the
Shimonoseki-kaikyo (strait) between Honshu and Kyushu
( FiGuRE II - J 07). Islands fringing the southern or Inland Sea
margin of Honshu are included. Major dimensions of the re-
gion, including the islands on the south are 285 miles east -
west, and 80 miles north - south. On the west, the peninsula
tapers to a width of 33 miles north - south.
Highlands of moderate height, 2,000 to 4,000 feet, dominate
the peninsula (PLAN 38). Gently rounded or flattish crests are
common, but most side slopes are steep. A few small, irregular
plains are scattered along the south coast, and 1 group
of such lowlands occupies the center of the north coast. Scat-
tered hills dot the small plains, and reduce the continuous level
areas to 5 or 6 miles at most. Interlocking nets of valleys pene-
trate the highlands deeply at several points (PLAN 40). Many
other valleys cut far back into the highlands, and at several
places parts of valleys are connected by low passes and form
passageways across the peninsula. All of these passageways as
well as the valley nets are deep, narrow, and crooked throughout
most of their courses, and can be blocked at numerous points.
The islands in the Inland Sea resemble the neighboring main-
land areas, as most of them are hilly with small pockets of low
level land.
Lowland soils are mostly loam in the southeastern section
and clay with some loam in the remaining areas. Upland
slopes have thin soils, mostly coarse sand and rock with some
clay.
Vegetation on the plains and in the valleys is dominantly
wet-field rice. Even the narrow tributary valleys in the higher
uplands have strings of tiny rice fields, most of them soaked
and muddy the year around. Small patches of dry-field crops
are on the unirrigable flat areas and lower slopes near most
villages. Uplands are in mixed needleleaf and broadleaf forest
with many extensive areas of coarse grass on middle and higher
slopes. These grassy openings in the forest are larger and more
widespread toward the eastern and western ends of the region.
Terrain subdivisions of Western Honshu will be discussed in
roughly counter-clockwise order beginning with the Tamba
Broken Plateau on the east and proceeding westward along the
north coast. Only the most significant subdivisions are pre-
sented in any detail.
( / ) Tamba Broken Plateau.
The Tamba Plateau is significant chiefly as a barrier upland
west of the highly strategic Kinki Lowlands of Osaka, Kyoto,
Biwa, and Nara. The plateau is roughly square, 60 miles east -
west by 65 miles north - south. A narrow section, maximum
width 8 miles, reaches southward to the coast west of KObe.
The plateau's most important characteristic as a military topo-
graphic feature is its broken nature; therefore, the western
boundary is placed arbitrarily west of the Maruyama-gawa -
Ichi-kawa passageway across the peninsula (ROUTE 34).
Long, narrow, mountainous Awaji-shima ( island) , 8 by 32
miles, on the south is included as an outlying part of this
region. General statements concerning the region apply also to
the island. Awaji-shima has military significance in that it
separates the waters of Harima-nada, Osaka-wan, and Kii-
suida, and thus dominates the water approaches to the critical
Kinki Basins.
The Tamba Plateau uplands are low, 1,000 to 3,500 feet, are
round or flat-topped, and are cut into numerous ridges and
blocks by narrow, winding, steep-sided valleys, and by larger,
1- to 2-mile wide, basin-like depressions. Several of the larger
valleys from opposite coasts are linked by low passes or interior
basins, and thereby form long, narrow, low, but difficult
passageways across the region. All of the passageways are now
utilized and have either highway or railway lines. The most
important of these routeways have been discussed previously in
connection with the western gateways of Osaka and Kyoto
Lowlands and are discussed further under Topic 27 (RouTEs
32 and 31). None of the passageways is a true corridor; all are
quite difficult in spots, with many narrows and commanding
heights. The routes can be blocked easily at such points.
Soils and vegetation conform to the basic pattern for West-
ern Honshu. Lowlands have mostly clay and loam soils and
uplands have a thin, rocky, clay soil. Vegetation in the valleys
and narrow basins is chiefly paddy rice with some dry crops;
vegetation on the uplands is chiefly forest, with many grassy
areas.
Deployment is almost impossible in this region. Cross-coun-
try movement is least difficult in the valleys and small basins,
but there it is handicapped by muddy rice fields and numerous
farmsteads, streams, and commanding heights.
(2) Matsue-Tottori Coastal Lowlands.
These lowlands, on the north coast, are a series of small
deltas. Some of these deltas are connected by fairly level routes
along the outer slopes of a line of large volcanoes. Low but
rugged hills reach the coast along the south shores of Shinji-ko
and Nakano-umi and near the town of Aoya. These rough
stretches form low but fairly effective barriers between adjacent
delta fiats. The region extends 90 miles east - west and a maxi-
mum of 3 to 6 miles north - south. These maximum distances
reach to the heads of the deltas. At the western end of the region
is the Shinji-Matsue-Yonago trough which lies between the
mainland and a hilly, 43-mile-long offshore peninsula to the
north. Deltaic deposits have filled in the 3-mile wide mouth of
the western embayment of this trough, thus forming a small
plain (FIGURE II - 23). The head of the western embayment,
now blocked off from the sea, forms Shinji-ko. East of this lake
is a rocky isthmus, to the east of which is Nakano-wan and a
long curved sand spit which separates Nakano-wan from Mio-
wan and the Sea of Japan. The sand spit curves northwestward
11 miles from Yonago and is 2 miles wide. Most of the spit area
is nearly flat, and forms a small sandy plain. The 40-foot dunes
on this spit and the 40- to 150-foot coastal dunes south of
Taisha and north of Tottori, are the most notable minor relief
features in the region.
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FIGURE II - 23. NIatsue-Tottori Lowlands, Western Honshri.
Dry crops on Shinji Plain. Looking SW. Note farmstead windbreak,
a..so steep, rugged mountain in background. 1931.
Uplands rise 600 to 1,100 feet in the areas north and
south of the Shinji-Matsue-Yonago trough, and on the land-
ward margins of the other deltas. Between the eastern (Kura-
yoshi-Tottori) deltas, isolated and roughly conical volcanoes
rise 4,000 to 5,000 feet, but the summits are 8 to li() miles
inland. All these highlands have steep middle and upper slopes
covered with forests and patches of coarse grass.
Vegetation of the lowlands is chiefly wet-field rice on the
flatter areas, and dry crops, chiefly mulberry, on the coastal
dunes and lesser sand ridges.
Soils are sandy in the coastal areas and in strips marking old
dune sites farther inland. Other delta soils are .clay and clay
loam. The uplands have thin sandy soils with much loose rock
on the slopes.
The lowlands are so separated by the Shinji-Nakano water
bodies and rocky slopes that only restricted deployment is pos-
sible on the separate low flat areas. Even there, deployment
and cross-country movement are greatly restricted by streams
and large drainage ditches, by numerous farmsteads on the
raised sandy (old beach-dune) ridges, and by the widespread
rice fields which are muddy even in winter. An additional local
handicap to both movement and ground observation is
rn-
posed by rows of 20- to 40-foot high tree windbreaks on the
northern and western sides of farmsteads.
Cross-country movement is even more difficult in the upland
border and high dune areas. There the chief handicaps are
steep slopes, loose sand- and rock-soil? and forest cover.
The Matsue-Tottori Coastal Lowlands have no easily tra-
versed natural gateways (Roums 36, 37, and 40). A first-
class railway and a highway run east and west along the Japan
Sea coast and connect the lowlands with other coastal areas.
These routes use many sharp turns, however, and pass through
numerous cuts in order to get around the rocky headlands. The
railway is forced to tunnel through some of the steeper spurs.
Similar turns, cuts, and tunnels are used by the railways and
roads which lead southward across the peninsula from Shinji,
Yonago, Kurayoshi, and Tottori. These routes can be blocked
easily at many places in the 50- to 60-mile sections which lie
in the more difficult parts of the highlands.
3) Western Honshu- Rugged Highlands.
This region includes the mountainous interior of Western
Honshu westward from the Tamba. Plateau. It reaches only the
north coast, to the west of the Shinji delta area. The highlands
of this region are mostly steep-sided, round- or flat-topped
blocks separated by narrow winding valleys (Fruit:JAE 24).
They decrease in average elevation from around 2,000 feet on
the east to slightly under 1,000 feet on the west. Scattered
peaks, many of which are volcanoes, rise above these levels and
reach 4,000 to 5,000 feet. Although average elevations are not
high, slopes are steep, most of them being well in excess of 30
per cent (PLA N 40).
Most soils are sandy with clay areas in the scattered valleys
and ridge-top flats. Much loose rock is mixed with the thin
soils on slopes.
Vegetation is dominantly forest with many grassy openings,
including recently cleared sections of the flatter ridge tops.
-These open grassy areas are located chiefly on the flat-topped
blocks near the western border. Tiny rice fields occupy the less
steep sections of the valleys and parts of the lower slopes.
-Patches of dry-crop land are on upland flats and near the scat-
tered farmsteads in the valleys.
Deployment is possible to a very limited extent in the few
scattered segments of wide valley bottomland and on some of
the larger of the ridge-top flats. Cross-country movement is
extremely difficult due to steep, -rocky forested slopes, to the
absence of corridor or valley openings longer than a few miles,
and to the presence in the valleys of wet rice fields, numerous
farmsteads, and swift unbridged streams. The routes which cross
this region all have segments of exceptional difficulty (RouTEs
36, 37, 40, 41, 44, 45, and 46).
(4) Western Honshu Broken- Lands.
This region comprises the southern coastal areas, the tribu-
tary inland areas, and the adjacent islands of Western Honshu.
It extends eastward for 225 miles from the narrow water gate-
way of Shimonoseki-kaikyo (FIGuRE II - 25) to the lowlands
FIGURE II - 24. Western Honsha Rugged Highlands.
low but rugged mountains of western Honshu greatly limit
deployment and cross-country movement. 1931.
FIGURE Ii - 25. Western Honshii Broken Lands.
Shim.onoseki-kaiky6, Honshu, looking N. Low, steep, forested hills
of western tip of Honshn rise directly from the
shore of the strait.
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around Himeji (FIGURE II - 26). Including the island groups,
the region varies from 15 to 60 miles in width north - south.
This region is distinguished from the rugged mountains on
the north by numerous flat-floored valleys and small basins
which form complicated nets. These valley nets reach 50 to 60
miles inland and converge to form small spider-like basins
around Miyoshi and Tsuyama. Similar valley groups, plus ex-
tensive delta fills around inshore islands, have produced an ir-
regular hill-dotted coastal plain in the Fukuyama-Okayama
area (FIGURE II - 27 ).
Hills, ridges and upland blocks which surround, and, in
places, invade the lowland are round-topped with smooth,
moderately steep-sided slopes (FIGURE II - 28). Heights range
from 800 to 2,500 feet. The uplands have thin, sandy, rocky
soils, and a spare forest cover, much of which has been cut
over repeatedly by charcoal burners. Grassy openings in this
forest are smaller, fewer, and farther apart than in the higher
uplands to the north. Lowlands have mostly sandy loam and
clay soils in the larger valleys and coastal plains, with some
sandy clay soils. Landforms and soils on the islands are similar
to those just described (FIGURE II - 29), except that lowland
areas consist of coastal strips and pockets rather than valleys,
and only the large eastern and western islands, such as Shodo-
shima and Yashiro-shima, have many heights over 1,500 feet.
Most of the flatter lowlands and parts of the lower slopes
have been leveled or terraced and made into paddy fields. Many
small areas of dry-field crops occupy dry terraces and lower
slopes especially in the central Fukuyama-Okayama area (FIG-
URE II - 30). A special wet-field crop which competes with
rice for space in the flooded lowland fields is "I", the reed
used to make Japanese "tatami" floor matting.
Deployment and cross-country movement are possible in
the plains, basins, and larger valleys but encounter the usual
difficulties found in restricted Japanese lowlands; these are:
flooded rice and "I" fields ( less muddy from September to
May), and numerous streams, canals, and villages. Many
commanding heights overlook the valleys; and outlying hills
furnish potential emplacements even in the larger basins and
coastal plains. Cross-country movement is possible also in the
uplands but is greatly restricted by prevailing steep slopes, loose
rock, forest cover, and commanding heights.
The chief natural gateways of the Western Honshu Broken
Lands are: westward across the narrow Shimonoseki-kaikyo to
FIGURE H - 27. Western Honshu Broken Lands.
Okayama, looking N. Narrow coast strip section of Okayama Lowland,
backed by typical low rounded hills with thin
soil and forest cover. 1919.
FIGURE II - 28. Western Honshu Broken Lands.
Mountains inland from Hiroshima. Cross-country movement is
difficult along routes through the highlands of Western
Honshil. Note rocky soil and thin forest cover.
FIGURE II - 26. Western Honshu Broken Lands.
Himeji Plain, looking N. The Himeji-Yashiro Lowland is a series
of flat strips among hills and ridges. 1922.
FIGURE II - 29. Western Honsha Broken Lands.
Omi-shima. Looking W. Typical cultivated pockets, and barren
hills on islands of Inland Sea. Note wet rice fields and
terraced lower slopes. 1933.
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the Moji-Yawata industrial area of northeastern Kyushu, east-
ward to the Himeji Lowland, and northward to Senzaki on the
northwest coast of Honshu. The Shimonoseki-kaikyo has been
underpassed by railway tunnels, and is now a land as well as a
water link. The eastward outlets to Himeji are 2 winding valley
routes from Tsuyama and Okayama. Railways and high-
ways now use these valleys, but forested commanding heights
up to 1,500 feet make the passageways difficult: as natural
routes. The route northward from 'Ube on the Inland Sea to
Senzaki on the japan Sea, near the western end of Honshu,
passes through similar winding valleys below forested heights
of 500 to 2,000 feet (RouTE 4.6). The higher ridges and nar-
rower valleys are encountered in the northern part of the route
where it leads through the western end of the rugged interior
highlands of Honshil.
FIGURE II - 30. Western flonshri Broken Lands-.
Inland Sea near Tomo. Looking eastward. Dry crops on terraced
lower slopes of broken land along the Inland Sea. Note
rugged islands in background.
(-5) Flinteji-Yashiro Lowland.,
This small, irregular lowland is a series of converging al-
luvial valleys cut back into rugged dirt hills 300 to 600 -feet
high, above which rise low, rounded, rock-ridges and blocks
800 to 2,800 feet high. The lowlands of the region are small
delta plains backed by a close net of flat-floored valleys (FIG-
URE III - 26) . The entire region including hill belts and isolated
heights extends 18 miles north - south and 25 miles east - west.
Its location west of the strategic Osaka Coastal Plain increases
its importance.
Lowlands have mostly loam soils with some sandy areas.
Wet rice fields occupy almost all flat areas and lower slopes.
A few patches of dry crops are near settlements; and thin forest
occupies the hills and rocky uplands. Soils on these uplands
are coarse alluvium on the hills and thin, sandy, rocky types
on the higher ridges.
Deployment and cross-country movement are possible in the
lowlands oat such operations must allow for commanding
heights except along the coast, for rice fields which are muddy
most of the year, and for numerous agricultural hamlets,
streams, and large drainage ditches. Cross-country movement is
also possible in the hill- and rock-ridge areas but is handicapped
by steep slopes, rocky soil, woodland, and commanding heights.
The region has no broad, level, natural gateways; but 3 pairs
of routes, each used by a railway and a highway, lead re-
spectively westward, northward, and eastward ( ROUTE 34 ) .
All of these passageways conform to the main type found in
western Honshu and follow fairly deep, narrow, and generally
winding valleys or coastal sills. These routes are not treated
here because they have already been discussed in connection
with the Western Honshu, Tamba Broken Plateau, and Osaka
Basin regions.
22. Drainage and Water Supply
FIGURE 11 - 109 shows the drainage pattern of Southwest
Japan.
A. General.
There are no rivers in Southwest Japan comparable
to the large rivers of continental areas, as barriers to cross-
country military operations. Drainage has a significant bu.t sec-
ondary influence upon such operations, however, particularly
on the lowlands. The great majority of Japan's rivers have
short courses, and flow through deep, narrow gorges in their
headwater areas, debouching suddenly upon flat to gently slop-
ing coastal plains or interior basins. In their upper, mountain-
ous reaches, the streams are rapid, have a high rate of flow
considering the small size of their catchment areas, and have
rough, rocky stream beds, but they do not present any greater
difficulties than the general terrain through which they flow
(FIGURE Il - 12). In the lowlands, streams normally consti-
tute only minor hindrances to movement, but on occasion they
may become major barriers; there is always the threat of floods
following severe storms in the summer months or following the
destruction of storage or power darns upstream. Few of the
rivers of the plains have deep channels; instead, they tend to
flow in broad, debris-choked beds, with many islands, and sev-
eral ill-defined, shifting channels (FIGURE II - 31). Near the
mouths of the larger rivers, however, particularly in the vicin-
ity of the coastal delta cities, the channels have been canalized,
and few fords are available.
Few of the rivers could be considered as effective water bar-
riers; nevertheless, the dikes and natural levees that parallel
the lowland streams, and the low alluvial terraces that also are
common along many such streams, form natural bunkers.
These are well-adapted for defense against enemy movement
laterally across the lowlands. The rice paddy fields that cover a
large area of lowlands are a drainage element of no
little significance to military operations (FIGURE II - 32).
During -practically all of the year they would be traversable
only by foot troops or by certain types of tracked vehicles. Al-
though most of the irrigation ditches are small and shallow,
and would not hinder troop movement materially, some of the
larger main-diversion ditches would be troublesome (FIGURE
1.1 - 33 ) . Irrigation ponds and "tanks" are common on many of
the larger lowland areas. Their close spacing and depth--com-
monly 3 to 8 feet--would make them effective tank traps,
especially when supplemented by minefields. Some of them are
elevated a few feet above the level of the plains, and if
drained, would provide numerous defensive bunkers.
Swamps and marshes are insignificant areally in Southwest
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FIGURE 11 - 31. Uji-gawa, Kyjto Basin,
Looking SE. Shallow stream with debris-choked channel, at point
where river enters interior basin from mountains. August, 1933.
_FIGURE II - 32. Rice field, Honshu.
Water several inches deep in rice fields will make movement difficult
across most of the lowlands of Southwest japan in summer. Many
of the fields remain muddy throughout the year.
FIGURE II - 33. Main irrigation canal near Ogori.
FIGURE II - 34. Kiso-gawa, Honshu.
Rafts on the turbulent Kiso-gawa.
Japan. Most areas which once were swampy or marshy have
been drained and adapted for rice cultivation.
Abundant supplies of water generally are available in nearly
all parts of the area. The only possible exceptions would be on
small off-lying islands, and in some of the isolated inland basins
during occasional drought periods. The gravels and sands of the
lowlands provide a good supply of water in shallow wells at a
depth of 30 to 100 feet. Such wells supply approximately half
the total population. On the alluvial terraces, wells would have
to be considerably deeper. Municipal water supply systems
utilize artesian wells, springs, rivers, lakes and ponds. Disinfec-
tion of municipal water supplies is not common, filtration
being the principal method of treatment; therefore the danger
of pollution is always present, regardless of source, and all
water should be properly treated.
B. Rivers.
The upper, middle, and lower reaches of most Japanese
streams are in marked contrast, and are here described sepa-
rately.
(1) Upper reach.
The sources of nearly all streams in Southwest Japan
are in the mountainous interior of the islands. Tributaries are
short, and the collecting areas are small. Because of the steep
slopes, run-off is extremely rapid. Stream gradients are steep,
and falls and rapids are common (FIGURE II - 34). Hydro-
electric power resources have been developed extensively in
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Japan. Water storage dams are found on the upper reaches of
most of the larger streams. Besides these, many of the smaller
streams have small clams for use in the rice irrigation systems.
Detailed data on stream flow are available for the upper
reaches of the principal streams. These data indicate some
seasonal as well as regional differences. Selected examples cif
these are given on FIGURE 11- 109. The most consistent sea-
sonal regimes are found on Kyushu and the Pacific side cif
Shikoku. They all show remarkable peak flows during the sum-
mer months, particularly in June, July, and August. These cot-
respond to the unusually heavy rains occurring at that season.
On Honshu, peak flows often occur both earlier and later in
the year, from .April through October. -Also common on Hon-
shin., and mostly absent farther south, is a subsidiary .high water
period corresponding to the cyclonic rains of spring. The winter
months, November through February, are consistently low
water periods throughout Southwest Japan, although the mini-
mum flow may occur in any month of the year. Mean annual
stream flows are fairly uniform, the larger streams on Honshu
showing the greatest variation from year to year. Individual peak
flows, however, vary considerably from year to year. Data on
observations, however, are mostly for only 5- to 10-year pe-
riods, hence should not be considered to be wholly representa-
t ive of average conditions.
(2) Middle reaches.
The larger streams generally pass through 2 successive
reaches below their main catchment areas and before they reach
the coastal lowlands. The first is their passage across the interior
basins, where they temporarily attain many of the character-
istics of the coastal lowland reaches. After leaving the basins,
they flow through winding canyon-like valleys, with only a
narrow strip of valley flat between the towering valley walls.
These narrow valleys, like the upper reaches, have numerous
water storage dams, generally somewhat larger in size.
(3) Lower reach.
This portion of the average river course consists of its pass-
age across the coastal lowlands to the sea. At the upper portion
of this reach, the stream gradient suddenly decreases, and the
river bed becomes choked with sand? gravel, or cobbles. Com-
monly, the river is elevated slightly above the general level of
the plain. More or less paralleling the river course are dikes
which confine the river waters during flood periods. These dikes
ire spaced about 11/2 to 1 mile apart, on opposite sides of the
river. They are usually from 10 to 20 feet high, are wide
enough on the top for single-lane roads, and in -many places
are faced with stone on the river side. A considerable number
of the rivers have fairly consistent average depths exceeding 5
Feet in their main channels (FIGURE - 109), but shifting
sand and gravel bars interfere with river navigation. These
bars, however, provide possible sites for fording ( FIGuRE
11 - 31). In addition, the practice of diverting water from the
rivers to irrigate rice fields causes many of the streams to be
nearly dry during some periods in mid-summer. The boats that
commonly use the rivers of the lowlands are of very shallow
draft, usually about 2 feet. Many such small river craft go far
into the interior on the larger streams (FIGURE II - 35). Many
rivers are used also to float rafts of logs from the forests. AI-
FIGURE Ii - 35. Kiso-gawa, Honshrl.
Boats such as these can navigate stretches of the mountain
streams of interior Honshil.
though many of the streams have an appreciable current on the
lowland reaches, it would not be very difficult to throw pontoon
bridges across them, for the banks are quite firm, and the
gravel, sand and cobbles of the bottom would provide good
anchorage (FIGURE - 36). Muddy banks and bottoms are
unusual in Southwest Japan. Broad, bare, sand and gravel flats
border most of the downstream river courses (FIGURE II - 37 ).
(4) Canalization.
Most of the larger cities of Southwest Japan are ports, lo-
cated on the deltas of the larger rivers. To accomodate the
large volume of shipping that enters and leaves these ports.
many of the multiple river mouths in the vicinity of the ports
have been deepened. These channels are bordered by artificial
levees, commonly faced by stone or by wooden piling. The
numerous channels in or near Osaka, Nagoya, Hiroshima, and
other Inland Sea ports would be effective elements in the de-
fense of these cities. In some of the larger cities of the interior
plains, such as Kyoto, the stream courses have also been deep-
ened, narrowed, and confined.
C. Lakes.
The lakes of Southwest Japan appear to have little signifi-
cance to military operations. Most of them are very small, and
consist mainly of volcanic crater lakes, water reservoirs, or
stream mouth lakes dammed by dunes or beach ridges. Biwa-ko
is the only really large lake in the area, and is located north-
east of KyOto. It is a deep lake, and presumably would be suit-
able for float plane use, although mountains rise steeply on its
western side. The many sheltered harbors along the coast, how-
ever, provide much more suitable seaplane anchorages than do
inland water bodies. The influence of the thousands of storage
ponds of Japan on military operations has already been dis-
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FIGURE II - 36. Bridge at Uji, Kyoto Basin, Ilonsh17.
Bridge over a part of the middle reach of the Uji-gawa. Looking N.
This stream is shallow, but the current is swift. August 1933.
FIGURE II - 37. River in Honshfi.
Wide, shallow lower course of a Japanese river. Note firm
levee bank in background.
cussed. Specific areas where these ponds are especially numerous
are in northeastern Shikoku east and west of Takamatsu, in the
Nara Basin south of Kyoto, on the Osaka Plain, on the Himeji-
Akashi Coastal Plain, on the plain west of Tamashima, and on
Awaji-shima ( island ) in Harima-nada.
23. Soil Trafficability
A. General factors affecting soil trafficability.
Soil trafficability refers to the capacity of soils to support the
movement of military vehicles. It refers especially to cross-
country movement of vehicles and to traffic on unimproved
roads made of local soil, rather than to traffic on improved or
surfaced roads. Soil trafficability is determined by the type of
soil (textural grade, organic matter content, and other profile
features), topography, vegetation, and weather factors. In this
Page II -25
area, the important weather factors are: precipitation (duration,
intensity, and character); temperature as it affects evaporation,
plant growth, and the freezing and thawing of soil; and wind,
cloud cover, and humidity, which affect evaporation of soil
moisture. Weather information used in this section was ob-
tained from Chapter V.
The general soil trafficability is moderately unfavorable in
this area. At most places the precipitation is high, ranging
from 50 to 190 inches annually, with the greater part of the
area experiencing between 60 and 80 inches. That part of the
area south of the central mountain ranges of Honshu experi-
ences a distinct dry period during November through February,
and the consequent concentration of precipitation during the
remaining months results in periods of poor trafficability. Al-
though there is no very marked variation in monthly precipi-
tation in Honshu north of the central mountain range, the ter--
rain is generally less favorable than south of the mountain
ranges, and nontrafficable conditions during the winter months
are more common because of greater total winter precipitation
and snowfall.
The poorest trafficability conditions throughout the area ac-
company the torrential rains associated with typhoons and in-
creased cyclonic activity, particularly during September. During
this period, lowlands are often flooded by stream overflow,
and coastal lands may be swept by extremely high tides which
follow in the wake of typhoons. Rainfall of 8 to 30 inches in
24 hours may occur during the passage of a typhoon, and
vehicular movement is halted.
Over most of the area, precipitation falls on 140 to 220
days a year, and south of the central mountain ranges of
Honshu, rainfall frequencies resemble rainfall amounts in
areal and seasonal contrasts. North of the central mountain
ranges, particularly during fall and winter, precipitation is
usually light but frequent, and the number of days with pre-
cipitation equal to or greater than .004 inch ranges from 14 to
22 a month. Consequently, there is little time for the soil to re-
gain normal trafficability between successive periods of pre-
cipitation.
Moderately high humidity is characteristic of this region in
all seasons and impedes the rapid evaporation of soil moisture.
Relative humidity at all coastal stations ordinarily averages over
70 (); for the months with the lowest humidities, and south of
the central mountain ranges of Honshu it is particularly high
during summer.
In much of the area, snow on the ground is seldom an ob-
stacle to the movement of vehicles. This is particularly true on
the exposed southern coasts where snow usually falls on only
1 to 3 days during each winter. In the central mountain ranges
of Honshu and in the region north of them, snow usually falls
on more than 10 days a month during January and February
and, for short periods, will restrict the movement of vehicles.
The occasional soil freezing that occurs in most of the area
should not affect trafficability except insofar as it disrupts nor-
mal soil drainage. In mountain areas of Honshu, freezing occurs
more frequently, but even there it probably very seldom hardens
the soil sufficiently to support vehicles. If shallow freezing
occurs when the soil is already saturated, vehicles will break
through the crust, and trafficability will be poor.
It is evident, then, that the weather factors alone result in
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poor trafficability, at least seasonally. In addition, a large part
cif the interior of the area consists of rough mountain ranges,
where trafficability is poor regardless of soil or weather con-
ditions, and where vehicular movements are restricted to dis-
continuous coastal plains separated by mountainous headlands,
or to the usually narrow valleys extending into the interior. Fur-
thermore, much otherwise favorable terrain is used for wet rice
fields, and poor trafficability results over large areas. The gen-
eral distribution of rice land is shown on the accompanying
soil trafficability map (FiGuRE II - 110). Detailed distribution
of rice land is shown on the vegetation maps (PLAists 41
and 42).
In areas oi: favorable terrain, soil conditions are important
iP determining general routes of movement. The soil trafficabil-
4 map shows considerable variation in soil types in these areas.
In general, fine-textured and medium-textured soils cover
approximately equal areas. Clay constitu.ents predominate in
the fine-textured soils, which are slippery and muddy when-
, ever wet. The fairly even division of sand, silt, and clay con-
stituents in the medium-textured soils gives them more favor-
able drainage properties. Coarse-textured soils, which are gener-
ally trafficable except during heavy precipitation or when
flooded in river 'valleys, cover less area than the other types.
B. Soil trafficability by regions an.d seasons.
The legend on FIGURE II - 110 is self-explanatory insofar as
it indicates the relative trafficability of the different soil types
in their natural state. Caution is urged in the use of the map,
since it gives an over-all view of the soils and soil trafficability
rather than detailed information for any one place.
The central mountain ranges of western Honshu constitute
an important climatic and soil trafficability boundary for South-
west japan. The part of Southwest Japan south of that boun-
dary is treated below under (1), (2), and (3). The area north
of that boundary is treated under (4).
Considering the southern area as a whole, the most favorable
trafficabiLty conditions occur in southern Kyushu and along the
shores of the Inland Sea. The period of most favorable traffic-
ability is during November through February, and there is
usually a shorter favorable period, during August, in the pro-
tected areas adjacent to the Inland Sea. Conditions are model-
tely to extremely unfavorable during June and July, and are
least favorable of all during September.
(1)
On Kyiish, soils having favorable trafficability are partic-
ularly widespread south of the 32' parallel and extend in a
narrowing strip northward along the east coast to Nobeoka.
In this area, the inland soils are predominantly ash barns which
drain rapidly. Where terrain and land use permit, these ash
loarns afford good cross-country- trafficability except during and
immediately after heavy precipitation. Coastal sands which are
usually trafficable occupy an almost continuous strip along the
east coast between Miyazaki and Nobeoka. Medium-textured
soils of somewhat less favorable drainage than the ash barns
of the south are common in the lower valleys of northwestern
Kyushu and on the east coast between Beppu-wan and Tsurturi-
zaki. In other northern areas of Kyushu there is a predominance
if clay soils which are nontrafficable when wet to the extent of
being generally slippery and muddy and locally causing miring
of vehicles engaged in cross-country movements. In addition,
there are large areas of wet rice fields extending inland from
the coast.
(2) Shikoku.
On Shikoku, the most favorable soils occur in northern
coastal areas from Mitsuhama to Sambommatsu, and on the east
coast from Muya to Murota-zaki. Coastal and alluvial sands are
particularly common along the north coast. The drainage prop-
erties of the medium-textured soils are similar to those of north-
ern Kyushu, and they are trafficable except during and immedi-
ately after medium and heavy rains. Wet rice fields are also
common in northern and eastern _Shikoku. Fine-textured soils
having poor drainage combine with high rainfall to produce
general poor trafficability throughout the year in southern
Shikoku.
(3) Western Honshu south of central mountain ranges.
South of the central mountain ranges on Honshu, -medium-
textured soils predominate east of 132', although large areas
are planted to wet rice. The coastal sands occur as discontinuous
strips, which are most common in the vicinity of Hiroshima.,
Ushimado, Osaka, and south of Hamamatsu. Fine-textured soils
are especially localized in areas west of 132', in the vicinity of
Miyoshi, and on the peninsula which extends south of Nagoya
into Ise-wan.
(4) Western Honshii north of central mountain ranges.
Most of the terrain in this area is rough and unfavorable for
cross-country vehicular movements, regardless of soil or weather
conditions. Furthermore, fine-textured clay soils, which are slip-
pery and muddy whenever wet, predominate in the short nar-
row valleys. Wet rice fields also are common. There are dis-
continuous coastal strips of well-drained sandy soils, however,
between 132?E and 135'E. The areas west of 132?E, and
along the southeastern shores of Wakasa-wan are particularly
unfavorable.
Although seasonal differences in trafficability are not as great
in this area as they are south of the central mountain ranges,
the most favorable period occurs during April and May. There
is also a less well-defined favorable period during August in the
area west of Miyazu. The least favorable periods occur in Sep-
tember, during December through March, and during June and
July.
24? Vegetation
Vegetation distribution is shown on PLANS 41 and 42, which
should be studied concurrently with the text. The small scale
of these plans makes it impossible to show minor areas. De-
tailed analysis of vegetation distribution can be made from the
Japanese Imperial Land Survey Department topographic maps
1:50,000.
A. General.
About 50 per cent of the non-urban area of Southwest Japan
is in forests; about 17 per cent is in cultivated crops; and some
2 per cent is in villages, dwelling sites, lakes and rivers; the
remainder is miscellaneous wasteland including grassland, bar-
rens, and scrubland
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FIGURE II - 38. Shrine at Nara, Honshrt.
Concealment is provided by large trees in shrine grounds, typical
throughout Southwest Japan. 25 April, 1914.
The most significant effect of vegetation on military opera,
tions is that, with few exceptions, wheeled vehicles will not be
able to deploy freely off the roads. Steep slopes are almost
universally forest-covered; and the low, flat lands are mainly
in rice paddies (where rice is grown in flooded fields; also
called "wet rice"). The dikes, drainage and irrigation ditches,
and mud of these paddy areas effectively prevent deployment
FIGURE II - 39. Rice ripening, Honshu.
Some concealment is possible in rice areas. The women are
gathering beans growing on the paddy field dikes.
FIGURE II -40. Bamboo grove, Kagoshima, KyRshri.
This stand of bamboo is in a private garden, but is fairly typical
of bamboo clumps in forests or around villages. 16 March, 1914.
of wheeled vehicles (FIGURE II - 32). Tracked vehicles, how-
ever, may deploy freely over most of the lowlands. The pre-
dominant vegetation along the beaches consists largely of
groves of black pine, which are fairly easily penetrable, but
afford considerable concealment.
Troops operating on the lowland areas will be almost con-
stantly in the open, with little concealment from air observa-
tion. The best concealment on lowlands is found in the villages
and about temple sites (FIGURE II - 38). Near the coast of the
Japan Sea, closely spaced rows of trees act as windbreaks
around farm buildings, and offer some concealment. When
prone, foot troops will be able to find a little concealment in the
rice paddies, particularly when the rice is fully grown and is
ripening ( FIGURE II - 39 ) .
Deployment of foot troops is relatively easy on the lower
slopes of the hills. Here most commonly are found the tea or
mulberry groves, fruit orchards, and fields of dry crops, such as
wheat. Where these slopes are forested, they are likely to be
planted to groves of pine or cryptomeria ( Japanese cedar).
All are easily penetrable by foot troops. Bamboo thickets are
numerous and vary as to penetrability (FIGURE II - 40). Open
scrubland and grassland are found mainly high up on the
hills.
Paratroop landings could be effected easily in the rice pad-
dies and dry-crop fields. The scrub and grassland of the hill
country may be suitable over small areas for paratroop or
glider landings, but slopes are generally too steep or too broken
up by valleys.
In the rougher mountainous parts of this section of Japan,
the forests are dense, with much undergrowth. The difficulty of
penetration accentuates the ruggedness of the terrain, and cross-
country operations in such areas will be largely confined to
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trails. Limited quantities of construction timber will be found in
almost any part of the area.
U. Description of uncultivated vegetation types.
The description of the dominant vegetation types in the para-
graphs that follow does not conform exactly to the groups
shown on the map of vegetation distribution (Plans 41 and
'12). All types of forest are grouped together on the map, bat
the various types and their general distribution are described
below. Mulberry is included in "orchards" on the map. Tea is
included under "dry crops."
Most uncultivated vegetation is located on the hill and moun-
tain areas that are too steep for cultivation.
The major type of uncultivated vegetation is forest. Japan-
ese forests consist of both broadleaf and coniferous ( cone-bear-
ing) trees, in either pure or mixed stands. A much smaller part
of the areas of uncultivated vegetation is in scrub or grass.
( I ) .6roadleaf evergreen forest.
A variety of sub-tropical forest composed of trees with broad,
evergreen leaves covers a large area in Southwest Japan. Com-
mon trees in this forest include various species of the "live" or
evergreen oaks, similar to those that are common in the extreme
southern part of the United States. Other broadleaf ever-
green trees associated with the oaks include various members
of the laurel family (one of which is the camphor tree), and
hollies (F[GIJ RE 11 - 41). In the southern islands there are
relatively large areas containing live oaks and an undergrowth
of evergreen shrubs almost exclusively. Pure stands of this type
of forest are progressively less extensive as one proceeds north-
ward through Southwest Japan and are found mainly in the
more inaccessible parts of the area. In nearly all sections of
Southwest Japan, barring high altitudes, representative species
are found mixed with other forest types. The upper ( elevation)
limit of their occurrence gradually descends northward, and is
at sea level at the northern boundary of this study. Toward the
northern and upper boundaries of this forest, deciduous trees
( trees that lose their leaves seasonally) become mixed with
the evergreens.
FIGI.:RE 11 - 41. Broadleaf evergreen forest, Yakusbinza.
Yakushima is a small island 35 miles south of Kyashii. Note
occasional conifers and much undergrowth. Typical also in
Southwest japan. 24 February, 1911.
FIGUR - 42. Coniferous forest. Y akushinia.
Natural forest composed mainly of conifers of varying
This type of forest is also typical of Southwest
Japan. 24 February, 1914.
sizes.
The trees of the broadleaf evergreen, when allowed to
mature, attain a diameter of 1 0 to 24 inches at the butt. In-
dividual trees in temple grounds and parks sometimes reach a
height of 100 feet, with a diameter of 3 feet. The overhead
canopy of a broadleaf evergreen forest is not regular in height.
The undergrowth is generally fairly dense, consisting of tree
ferns, bamboo grass, vines, and small trees. One of the many
tropical vines in these forests is known as the "iron creeper";
its cords are so strong that they are often used to support
bridges. There is little seasonal change in the forest. Penetra-
tion by foot troops is slow and difficult, but there are well-kept,
though steep, trails throughout the forest areas. These trails
provide relatively good means of communication.
(2) Coniferous forest.
Pines, firs, hemlocks, and cryptomeria constitute a significant
element in the forests of Japan. They are frequently mixed
with broadleaf trees throughout Southwest japan (.FEGURE
Ii - 42) and are used almost exclusively in Japanese reforesta-
tion projects. Of the pines, black pine is the most numerous in
Southwest japan. It has been estimated that about 20 to 30 per
cent of the forest area of Japan has been reforested; hence some
idea of the dominance of the conifers can be obtained.
The most common areas for planted conifers are found on
the lower slopes adjacent to the densely populated plains, and
above the mulberry and tea groves on the hillsides. Conifers
also are the most common trees of the temple grounds and
form the principal shade trees in villages. When found in pure
stands, as is the case particularly in reforested areas, the conifer-
ous trees are characterized by a regular spacing and by lack of
undergrowth; especially is the latter true when the stand is of
pine. As a rule, conifers are planted about 6 feet apart each
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way, and are thinned to a wider spacing in the older stands.
Such forests are easily penetrable on foot if slopes are not too
steep.
The cryptomeria is not only important as a source of lumber
but is also the most common ornamental tree; it is probably
more widely used for plantings than any other tree (FIGURE
II - 22). In temple grounds and along avenues where they are
not cut, these magnificent trees may reach a height of 150 feet
with a diameter of 4 to 8 feet. The red pine, also a popular
tree for planting, sometimes grows to a height of 100 feet
when allowed to stand, but trees in a forest are generally cut
before attaining such size. For 1/2 to 3A of its height, its trunk
is bare of branches. The fir also has a tall, straight trunk bare
of branches for 1/2 of its height. Where the black pine grows
closely mixed in a forest with other trees, principally the red
pine, it forms a nearly straight trunk, at maturity being 60 to
90 feet high with a diameter of 20 to 30 inches. More often,
the black pine grows as a single specimen or in scattered stands
open to the winds, and is a twisted tree with crooked, irregular
limbs. It is similar in appearance to the Monterey pine of Cali-
fornia. It is the most common type of vegetation cover on
coastal beach ridges and sand dunes. The wood is of less
economic value, except for fuel, than that of other types of
conifers, but is much used.
(3) Broadleaf deciduous forest.
This forest is found mainly at higher elevations in Southwest
Japan, although individual, species comprise a significant part
of the mixed forest described in the next paragraph. The prin-
cipal deciduous trees are oaks, some specimens attaining 50 to
60 feet in height. Other trees include the beech, maple, birch,
chestnut, ash, dogwood, honey locust, and sumac. As a general
rule, the trees of this forest are not as tall as those at lower
elevations, and are not as closely spaced, although the under-
growth is dense, bamboo grass being especially troublesome to
penetrate. Conifers are likely to be scattered here and there
throughout the forests, but are not dominant except in reforested
areas.
(4) Mixed forest.
in terms of area, this type of forest is by far the most common.
It may consist of mixtures of all the 3 types of forest de-
scribed in the preceding paragraphs, and in addition may in-
clude the thickets of second growth that follow clearing. It has
no general pattern of distribution, but is likely to be found
more at intermediate elevations and toward the north. The
mixed forest often represents stages in the natural regrowth
of the broadleaf evergreen forest. Mixed forests in various stages
of this replacement process may be found scattered throughout
Southwest Japan. No generalization can be made concerning
typical densities or size of trees in these forests, since they are
subject to great variation. Underbrush in the mixed forest gen-
erally is thick, and the majority of the vines, bushes, and shrubs
are evergreen. There is little seasonal difference in ease of move.
ment through the forest.
(5) Wasteland, scrubland, and grassland.
This open terrain constitutes a very appreciable part of the
total area. It includes areas covered with low brush and weeds,
those with a very sparse tree growth, areas denuded by mining
operations and volcanic action, the stretches of flats and hill-
sides covered with tall, coarse grass or .fernbrakes, and places
where bamboo grass is widespread (FIGURE II - 1). The largest
areas of the scrub wastelands will be found at or near hill sum-
mits or in areas of steep slopes where erosion has carried away
most of the top soil. Considerable areas of deforested land
where regrowth has not reached the stage of trees arc included.
Grasslands are not widespread on Kyushu or Shikoku, but are
extensive in southwestern Honshu, where they are found mainly
on north-facing hillsides and along the lower slopes of the
principal volcanoes. The grass is often of a tall coarse variety,
somewhat similar to the cogon grass of the Philippines or the
kunai and alang-alang of the East Indies. The blades have
sharp edges and will cut exposed skin of troops.
C. Description of cultivated vegetation types.
The pressure of population in Japan has resulted in ex-
tremely intensive use of all arable land. Rice is by far the prin-
cipal food crop, and paddy fields are universal in low, flat
areas. Other small crops are planted on the paddy field dikes.
Villages are compact. Fields arc small. Dry crops, orchards, and
tea and mulberry groves are found largely on slopes. Idle farm
land and pasture arc seldom seen, except seasonally. For this
reason, the vegetation of Japan is in close correlation with land
surface configuration (Compare PLANS 38, 39, and 40 with
PLANS /11 and 42) and helps greatly in the analysis of terrain
from aerial photographs, once the characteristic location of the
various crops is understood. Paddy fields, especially, should be
identified easily.
( / ) Paddy rice.
Paddy rice is a lowland crop, although some is grown in
terraces on the sides of hard rock hills, particularly in Kyushu.
Flat lands not in paddies are those with sandy or volcanic ash
soils. Rice constitutes about 54 per cent of the total cultivated
land in Japan; in Southwest Japan this figure would be con-
siderably higher.
On the flattish coastal lowlands there are multitudes of ir-
regularly-shaped paddy fields, or water-lily fields which have
many of the same characteristics, averaging about 1/10 to 1/8 of
an acre in size. These are enclosed by dikes 10 to 15 inches
wide and of about equal elevation (FIGURES II - 32). Generally
the expanses of paddies are interrupted here and there by vil-
lages, sometimes tree- or hedge-enclosed, rising like islands
above the inundated paddies. Elevated footpaths or roads tra-
verse the plains, usually in rectangular patterns. Irrigation and
drainage canals line fields and paths and there are numerous
ponds. In places, scattered dry fields, elevated 2 feet or more
above the paddies and bearing unirrigated crops, stand out
conspicuously above the lower rice fields.
The dikes of paddy fields arc more or less temporary and
are of mud or soil scooped out from the ditches, or fields. At
irregular intervals, however, a wider, usually permanent dike
carries a well-trodden footpath or narrow roadway (FIGURE
II - 43). Where the wet rice fields ascend the lower slopes of
the hills by means of terraces, the dikes, or terrace edges, are
rock-faced.
Irrigation canals are small, and generally are not the obsta-
cles to overland travel that they are in China, or in parts of
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India. Very few of them would be too deep to ford, although
the mud in them would tend to bog down wheeled vehicles.
The character of the paddy landscape changes with the
seasons. Spring is the time for the preparation and sowing of
rice-seed beds which by May or June make themselves con-
spicuous as they stand out in green patches on what may be
fallow, muddy plains. In early summer, with the transplant-
ing of the young rice seedlings to the paddies, the flooded
fields form a much-subdivided water surface pricked with the
shoots of the young rice plants (FfGuRE IT - 32). By mid-sum-
mer, the scene has changed, and green is the prevailing color,
the individual fields still being obvious, owing to the inter-
ruptions at the dikes ( FIGURE II - 39). Green changes to yellow
in au rumn, .ind after harvest, the plains look bare.
FRAJRE II - 43. Wide -path on paddy field dike.
Permanent dikes frequently carry a wide path. Light motor vehicles
can use the dense network of such paths on the lowlands
of Southwest japan. Straw stacks on right.
Probably 60 to 70 per cent of the paddy area of Japan re-
mains fallow during the winter season, much of it covered
with water. This means that a considerable area of the paddy
fields generally is a barrier to wheeled vehicles the year around.
The trafficability of paddy fields is improved somewhat by the
Firm "floor" of the fields, a relatively impervious layer which lies
beneath the mud.
The water depth in the flooded fields varies somewhat but
generally it is shallow and grades downward into soupy mud.
In general, troops standing in a flooded rice field will sink in
to a depth of 10 to inches. Vehicles will sink deeper.
Where the paddy fields dry out sufficiently to be planted in
winter crops such as wheat, barley, and rape, they are spaded
into a series of narrow, parallel ridges and troughs, the former
1:2 to IS inches wide and 12 inches high. Water frequently
stands a few inches deep in the troughs. The grain is sown very
thickly on these ridges in single or double rows. Wheeled
traffic in such fields would be extremely difficult.
Because the dikes; of paddy fields are usually planted with
beans, -vetch, rape, or occasional mulberry bushes; there is suffi-
cient horizontal concealment for a large number of foot troops
over a square mile of paddy rice fields. There is no natural
concealment from air observation. Gun positions would prob-
ably Ipe located in villages, temple grounds, or on adjoining
wooded slopes, utilizing the paddy fields ahead of them as open
fields of Fire,
(2) Dry-field crops.
Dry-field crops are found for the most part on the lower
slopes of hills bordering the lowland plains and river valleys,
and as winter crops on the better-drained paddy areas. Small
areas are also found on relatively level hilltops, gravel terraces,
and volcanic ash uplands. Grains like wheat, barley, unirrigated
rice, and naked barley are the common winter crops, sown in
the fall and harvested the following early summer. Vegetables,
particularly beans and sweet potatoes, comprise the principal
summer crops of the annual type on the dry fields, and are fre-
quently inter-tilled between the rows of grain in early summer
and fall. The dry fields, therefore, are seldom fallow at any
time of year. Like the paddies, the dry fields are very small.
Many small areas of dry-field crops, especially where they are
not continuous, could not be shown on the vegetation map, due
to limitations imposed by the small map scale.
Ridging of the upland fields for winter grains, similar to
the practice on the paddy fields, is common in some areas. The
irregular surface of the grain fields is not apparent from a
distance when the grain is fully grown, and then the fields
could afford some cover and adequate concealment for snipers.
This is all the more significant when it is realized that many
such fields are on slopes directly overlooking the flat, open rice
paddies below.
(3) Orchards.
Fruit orchards, although present in nearly all parts of
Japan, are small, many of them too small to show on the vege-
tation map. Furthermore, the area shown as orchards includes
mulberry groves. Citrus fruits, particularly oranges (manda-
rins), are the most common orchard fruits (FIGURE II - 44).
They are common on hillside terraces along the Inland Sea and
on the Pacific east of Ise-wan. Persimmons, loquats, and pears
are also found frequently, the last named tree in some places
occupying lowland sites, its limbs and fruit supported on hod-
2ontal wooden trellises. Orchards, although small in area, may
afford good bivouac areas. They furnish some concealment, and
deployment is easy.
FIGURE II -44. Citrus grove near Kagoshima, Kyfishza.
Fruit-laden citrus trees on slope of hill. Maximum height of these
trees about 18 feet. Grove bordered by forest. 3 March, 1914.
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FIGURE II -45. Tea gathering, Honshrt.
Flooded, irregular paddy fields on flat plain, bordered by terraced
hills. Tea garden in foreground. Villages on
higher lands of plain.
(4) Mulberry.
The mulberry is cultivated for feeding silkworms. It is a
small tree with a trunk from a few inches to a few feet high
and 2 to I inches in diameter. Shoots up to 30 feet in length
grow from this trunk and from the roots. During the summer
when there are leaves on the shoots, these shrubs offer consider-
able concealment. In winter the shoots are cut back and there
is little concealment. Plants are set about 5 feet apart. They
would offer obstacles only to the lighter vehicles.
The mulberry is found in small patches on most farms hav-
ing any hill land too steep for rice, and is mixed in among the
orchards and dry crops on the lower hillsides. In some places
it occupies river dikes or Hat lands with poor soil.
(5) Tea.
The small tea gardens of Japan occupy less than 8/10 of 1
per cent of the total area in dry crops. In Southwest Japan this
figure would be somewhat higher, but areally the tea gardens
are relatively unimportant, except locally. They arc found typi-
cally on steep hill slopes or on gravel upland surfaces (FIGURE
II - 45). Some tea is grown in small patches around the dwell-
ings in villages. The tea plants are grown either as hedges or
as individual bushes. They are about 3 to 4 feet high, and are
spaced about 3 feet apart. They would provide good conceal-
ment for snipers. Since the bushes are evergreen, this conceal-
ment would be available throughout the year.
D. Distribution of vegetation by terrain regions: Kyushu.
The distribution of vegetation in Kyushu is shown on PLAN
41. Because of the limitations imposed by scale this map is
generalized, and many of the smaller areas have had to be
omitted.
(1) Southern Kylishii Lowlands and Highlands.
The vegetation of this region includes more tropical and
subtropical species than does that of any other part of the
country. Probably less than of the highland area reaches an
elevation of 1,500 feet and only some 9 or 10 peaks rise slightly
above 2,800 feet, the general altitudinal limit of the zone of
evergreen oaks (PLAN 38). Thus, in the forests of Southern
Kyiishii there are many evergreen oaks, camphor and other
FIGURE II - 46. Mixed forest, Kirishima. Kyushu.
Mixed forest at base of Kirishima volcano. Large tree is 90 feet
high. Note bamboo in right background. 5 March, 1914.
species of the laurel family, hollies, magnolias, beeches, pines,
and other trees usually associated with them. The undergrowth
of the mixed forests is very dense and in addition to the usual
shrubs of the subtropical forest there are found here a variety
of tropical plants (FIGuRE 11- 46). Among these are tree--
ferns, cycas (between tree-fern and palm in appearance) and
lemons. Half or more of Southern Kyushu is given over to
forests, but only a small area is in conifers. These are scattered
in the hills and lowlands near the southern tips of the 3
peninsulas, on the lowlands back from the western coast of
Satsuma-hanto (peninsula), and in irregular patches over the
southern part of Miyazaki-Nobeoka Coastal Plain. Grassland
and scrubland occupy a relatively small part of Southern
Kyushu. It is impossible, however, from data available, to dis-
tinguish always between forest and scrubland; therefore, parts
of the area shown as forest on PLAN 41 may actually be scrub.
There are small patches of grassland along the southeastern arm
of Satsuma-hanto (peninsula) extending from Ikeda-ko (lake)
both ways along the ridge. Between Kagoshima-wan (bay)
and Ariake-wan there is much more grass, scattered in areas of
various sizes among the forests, and bordering many of the
paddy fields.
Lowlands which can be irrigated are devoted almost exclu-
sively to rice. 'these paddy areas occupy the narrow stream val-
leys and the coastal plains. The most extensive paddy areas in
Southern Kyushu are: from the southwestern coast of Ariake-
wan (bay) inland to Kanoya and Shimonaka at the head of
Kagoshima-wan (bay) along the Oyodo-gawa (river) north
and south of the town of Miyankonojo5; and along Hitotsuse-
gawa (river) where it crosses the Miyazaki Plain. Farther south
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on the Miyazaki Plain are various smaller rice areas. Narrow
strips of paddy fields also border the streams in their narrow
valleys between the higher terraces and farther upstream in the
hilly borderlands. Rice is harvested in this part of Kyushu in
late August.
Wheat is as important a crop as rice in Southern Kyushu.
Some of the paddy fields support this winter crop, but the
greater part of the wheat grows on the uplands. Wheat, barley,
and sweet potatoes are the main crops of the upland fields.
Vegetables, some fruit, mulberries and., to a limited extent, tea
share these fields. The most extensive upland areas devoted to
miscellaneous crops are at the southern end of Satsuma-hanto
(peninsula). Smaller areas of dry crops are found along the
western shore of the peninsula and on the slopes above the
head of Kagoshima-wan (bay). A relatively large area devoted
to malberries is on gently sloping land about mid-way between
Kagoshima-wan (bay) and Ariake-wan, northeast of the town
of Kanoya. Small, discontinuous, cultivated areas, which may be
surrounded by woods or grassland, in many places border rice
paddies, or lie on the slopes immediately above.
The volcanic cone, Sakura-shima, facing Kagoshima city,
has much rock surface exposed.
(2) Central Kyushu Mountains.
Sorie of the high mountain area in the south central part of
this region rises above 2,800 feet elevation and thus is above
the acne of evergreen oaks. Smaller areas on the upper slopes
of isolated peaks also lie above the evergreen oak zone. Such
areas are covered with deciduous forests interspersed with small
irregular areas of grassland. However, since the greater part
of the mountain surface lies below 2,800 feet, its forest cover
consists of broadleaf evergreen trees and mixed deciduous and
coniferous trees (FiGuBE II - 46).. Pure stands of coniferous
forest appear here and there (FIGuR1 II - 47), some of them
having been planted (FrGuRE II - 48). There are pure stands
of broadleaf trees also, but for the most part, the forests are
mixed. Passage through their dense undergrowth is difficult
( FreitiRE I.1 - 49). These mountain forests are an important
source of timber in Japan. Although the forests are more or
less difficult of access, timber for various purposes may be
obtained there.
The most extensive grasslands and scrublands of Kyushu
are in this central region. They occupy the greater part of a
belt some I 0 to 1-5 miles wide spreading southwestward from
die foothills near the head of Beppu-wan (bay) past Aso-zan
to the Kumamoto Plain. An isolated section of grassland lies
near the coast of Usuki-wan (bay ) ? and extends inland several
miles. A few limited areas .are devoted to paddy fields and other
cultivation.
The slopes of Futago-yama, the mountain forming the cir-
cular peninsula of Kuni-saki, are covered with successive strips
of paddy fields, forests, and grasslands. Enterspersed among
them on the lower slopes are small areas planted to dry crops,
fruit orchards, and mulberries.
In Central Kyushu are 4 important areas under cultiva-
tion. The largest of these is on the coastal plain along the
southern shore of the Suo-nada (sea). Paddy fields occupy
practically the entire plain. Some paddies lie fallow in winter;
others are covered with wheat or a legume. The second exten-
FIGURE II - 47. Coniferous woodland. Kylvishn.
Coniferous stand of scattered red pines and grass openings on
slopes of Kirishima volcano. Planted conifers in
background. 8 March, 1914.
FIGURE II -18. Kyushn. between Shim-bara and Unzen.
Block of planted conifers at center and left. Patches of scrub and
grass scattered over slopes.
FIGURE II -49. Dense forest on Yakushima.
Mixed forest, with cryptomeria and hemlock predominating.. Thick
undergrowth exposed along stream. Typical also of much of
Southwest Japan. 19 February, 1914.
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FIGURE II - 50. Terraced fields near Beppu, Kyushu.
Irregular, terraced rice fields near Beppu. After harvest the
stacks stand in fields which are rough with stubble.
sive paddy area borders a part of the southern shore of Beppu-
wan and extends southwestward up the Kata-gawa (river)
valley. Along the bay to the east of the paddy fields are upland
fields devoted to dry crops or terraced rice (FIGURE II- 50).
At various places on the foothills facing Beppu-wan ( bay) are
fruit orchards, although the areas are too small to show on
the accompanying vegetation map.
The Hitoyoshi Basin in the southern part of Central Kyushu
provides the third large cultivated area. The basin is some 18
miles long and 7 miles wide and is surrounded by mountains,
except for the gorge of the Kuma-gawa (river). Almost all of
the upper part of the basin and much of the lower part are
devoted to paddy fields irrigated by the Kuma-gawa. Many
fields on terraces are planted to other crops in winter. Several
of the mountain slopes enclosing the basin are cultivated, pro-
ducing vegetables, sweet potatoes, wheat, tea and mulberry.
The fourth important cultivated area is the upper valley of the
Kuro-kawa and is devoted almost entirely to paddy fields. A
narrow border of forest almost encircles this paddy area, sepa-
rating it from the surrounding grasslands.
In the extreme southwestern part of the region, facing the
Amakusa-nada (sea) the hills are broken by the valleys of the
Sendai-gawa and Komenotsu-gawa. These valleys are connected
by a narrow coastal plain. The Sendai-gawa and many of its
tributaries are lined with paddy fields for miles; at the mouth
of the Komenotsu-gawa is a fairly wide area devoted to rice,
bordered by dry-crop fields. The greater part of this southwest
coast, however, and of the northeast coast not already accounted
for, is backed by forests with some grassland.
(3) Northern Kyfishii Lowlands and Highlands.
Northern Kyushu is not typical of most Japanese regions.
Probably -Y3 to 3!=, of the entire region is in paddy fields, and
in addition more land is devoted to dry crops than in the regions
previously discussed. Consequently, a relatively smaller part of
the region is covered with evergreen broadleaf forest, grassland,
or scrubland.
The widest extent of paddy fields in the region is on the Saga
Plain bordering the northern shore of Ariakeno-umi (sea) and
Page II - 33
spreading northward and northeastward, connecting with paddy
fields of the Fukuoka Plain along Fukuoka-wan (bay). Thus,
practically the entire lowland around the head of Ariakeno-umi
is an expanse of mud and water throughout the year. Around
Fukuoka-wan and along the coast extending northeastward
from it, many of the paddy fields are planted to winter grains
or are planted to vegetables in early spring. Initial flooding of
the paddy fields for the rice crop is frequently delayed there until
mid-July, and the period of their flooding extends to late Oc-
tober or early November. In the block of hills in the northern
part of the region and in the high hills to the west are narrow
strips of paddy fields along the streams, and many small tracts
of irrigated terrace. The hills to the west are covered mostly by
forests in their eastern section and by grass in their western
section. Fairly extensive paddy areas lie between the northern
hills and the Suo-nada (sea).
The nearly continuous coastal plain extending southward
from the Saga Plain to Yatsushiro is devoted almost exclusively
to paddy fields. The relatively low hills a few miles inland are
covered for the most part by broadleaf evergreen forests, but
some of the lower slopes are planted to orchards. Between these
hills and the steep western face of the highlands of Central
Kyfishfi, east and northeast of Kumamoto, is an extensive area
of slopes used for dry crops. Mulberry bushes are planted exten-
sively there. The hilly, 10-mile long peninsula extending west-
ward from this plain is forest-clad, with a few patches of grass.
On the narrow lowland of its southern shore are many small
areas of paddy fields.
Many groves of the wax tree occupy the various hill slopes
of Northern Kyushu, where they are grown more extensively
than elsewhere on the island. The tree is small, growing to a
height of only 15 to 20 feet. It has a spreading crown and rather
small leaves. A grove of wax trees offers concealment and cover
approximate to those offered by an apple orchard.
(4) Northwestern Kyushu Broken Lands.
As in most of Japan, the predominant vegetation for this
region is forest of the broadleaf evergreen type, except on the
upper parts of Unzen-dake (mountain) and Tara-dake, which
rise above the evergreen zone. Where hills are close to the
shore, and in some places where they are not, the evergreen
forest skirts the coast or lies just back of it. From the only
available maps for the fortified area surrounding Sasebo it is
inferred that there are extensive grasslands in this area. The
lower courses and deltas of many streams of Northwestern
Kyushu are covered with paddy fields, and along several rivers
such fields extend relatively far inland. Most of the area planted
to dry crops is on the lower slopes of Unzen-dake and Tara-
dake. Paddy fields occupy terraces which ascend these lower
slopes. Grass borders much of the relatively steep western
coast of the Sonoki-hanto (peninsula).
E. Distribution of vegetation in Shikoku.
The distribution of vegetation in Shikoku is shown, to the
extent possible on a small scale map, on PLAN 12.
(1) Southwestern Shikoku Broken Lands.
This area of hills and valleys is mostly wooded. Only a
small upper part of a few mountains lies above an altitude of
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2,500 feet, the average altitudinal limit of the evergreen broad-
leaf forests in Shikoku. Thus, practically the entire region is in
the subtropical forest zone. Broadleaf evergreen, especially
oak, trees predominate but there are also many conifers. Near
the coast of Tosa-wan (bay) camphor trees are relatively .nu--
merous. Forests are more continuous in the south central part
of the region than elsewhere, although broken by some rela--
lively small grassy areas, and by irrigated rice paddy areas in a
few narrow valleys.
Many strips of paddy fields stretch inward from the coast,
.EolloNving the course of streams. These frequently are bordered
by cultivated slopes, many of which are occupied by mulberry
groves. In various stretches along the coasts of Hokkezu-wan
(bay) and Uwajima-wan, the cultivated slopes and terraces
skin: the shore; in others a margin of trees lies between shore
and crop. 1.-A)rests occupy the greater part of the area, however.
The connected valleys of the Shimando-gawa and the Matuda-
kawa form a fairly broad passageway across the southern part
of Shikoku., and are covered for the most part with paddy
fields; with dry crops, including mulberry groves, orange, per-
simmon, and pear orchards, barley, and sweet potatoes; and
with grasslands. In the northwestern part of the region mul-
berry groves and cultivated dry fields are fairly numerous.
More than half of the dry fields and paddy fields in Shikoku
grow both summer and winter crops.
(2) Central Shikoku Mountains.
This region is primarily a forested one. Perhaps ;'S of its
area has an altitude exceeding 2,500 feet. Thus the forests of
the region include the trees of the evergreen, broadleaf oak
forest on the lower slopes and valleys, and the trees of the
deciduous, broadleaf forest on the upper slopes. There are 2
important timber producing areas in the region. They are the
catchment area of the Monobe-gawa in the east, and of the
Shimando-gawa in the west. There are large areas of grassland
in the extreme western section of the region. These are mainly
on the ridges of the mountains, spreading irregularly down the
slopes. The upper half of the north-facing slopes of the long
cast - west mountain ridge overlooking the eastern part of
Hiuchi-nada is perhaps the most extensive grassland on the
island. Other sections with much grass are in the extreme
eastern part, and in a belt stretching across the region north-
eastward .1'rom the city of Kachi..
Relatively little irrigated rice is grown in this region except
near the eastern coast where many narrow valleys are filled with
long lines of paddy fields, and in the extreme northwest
whete a few. broader valleys are irrigated. In the mountains,
however, there are innumerable hillsides devoted to dry crops,
part of which is upland rice. In the vicinity of the towns of
Ochi and Ilkegawa in the western part of the region many hill-
sides are planted to a variety of the paper mulberry tree. Where
these are grown in the open they provide scant concealment
and no cover, for they are allowed to grow only about 6 feet
high and are cut nearly to the ground in November. Sometimes
they are grown under sumac trees.
(3) Kochi Plain.
A large part of the KOchi Plain is in paddy fields, bordering
the various streams that wind around its hills and cross it to
the sea. The largest of these paddy areas is in the eastern part,
watered by the Mon.obe-gawa and the Kokubu-gawa. Many
of these paddy areas extend almost to the sea, only a sandy
beach or fringe of pine trees intervening. Two crops of rice per
year are grown on some of these paddy fields. Thus they are
under water for a longer period than most paddy fields. The
first flooding takes place in late March or early April, and the
fields are drained for harvesting in late July or early August.
Flooding for the second planting takes place immediately after
the first harvest, and continues until the second crop ripens in
November.
Spread over some of the unirrigable lands in the northeastern
part of the region, adjacent to the Monobe-gawa, are exten-
sive mulberry groves. The Monobe-gawa and the Niyodo-gawa,
in the western part of the region, are both bordered by strips
of sand and gravel, mostly unirrigable and bare. Various small
sections, however, are occupied by mulberry groves, and some
parts are covered with coarse grass.
The hills are low, few reaching 1,000 feet in elevation.
These, with other uncultivated areas, are mostly covered with
forests of the broadleaf evergreen oak forest zone. Along parts
of the shore, particularly in the westernmost part, steep, forest-
covered hills rise from the rocky shores. East of the Niyodo-
gawa the shores are mostly sandy, and frequently tree-fringed
or forested. There is relatively little grassland in the region.
(4) Eastern _Shikoku Plain.
Cultivated crops :over almost all of this region, with the
exception of the belt of gravel and sand bordering the Yoshino-
gawa (river) from Hiruma to the sea. The few hills near the
coast reach an elevation of about 800 feet and are forested,
mainly with conifers, but among these are various species of
evergreen, broadleaf trees and shrubs. There is little grassland
in the region except on sections of the gravel and sand belt
along the Yoshino-gawa. Clumps of bamboo are found here and
there along the valley.
The greater part of the region is irrigable and is devoted to
paddy fields. These fields are, for the most part, in the wide
part of the area near the coast, but they extend in disconnected
sections all the way up the river to Hiruma.. Wheat or barley
is grown as a winter crop on approximately 50 per cent of the
paddy fields. A large part of the cultivated land in the narrow
\,alley, and some areas on the delta plain are occupied by mul-
berry groves. Other dry crops, besides vegetables and fruit, are
tobacco and indigo, neither of which provides concealment
from air observation.
(5) Northern Shikoku Lowlands.
The greater part of this region is in paddy fields, joined for
the most part in fairly large, irregularly shaped areas. On the
eastern peninsula they encircle many small hills. About two-
thirds of the paddy fields have winter crops, largely wheat,
barley, or vegetables. Some of the lower slopes of the hills, and
the various lowland areas which cannot be irrigated are devoted
mainly to vegetables, mulberry groves, and fruit orchards. A
relatively large area is planted in vegetables in the eastern
peninsula, and to citrus groves in the western one. Mulberry
groves are few in the greater part of the eastern peninsula, but
in the western part and elsewhere in the region they are fairly
numerous.
The large rivers of the region, including the Shigcnobu-
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gawa, the Nakayama-gawa, and the Doki-gawa are bordered
for miles by sandy-gravelly strips which support a sparse,
coarse grass cover in places.
Practically all the hills of this region are forested. Conifers
predominate and there are many pure stands of coniferous
trees. There are relatively large areas of scrub pine in some
sections. The region lies within the evergreen, broadleaf forest
zone; thus many of the trees and shrubs arc of evergreen,
broadleaf varieties. Along a great part of the coast, particularly
of the eastern peninsula, wooded hills rise from the shore, and
pines usually fringe the sandy shore even where the adjacent
land is low and devoted to crops. The region has little grass-
land although a number of hillsides have grassy patches.
F. Distribution of vegetation in West Central Honshu.
(PLAN 42).
( 1) Kii-hanto Mountain Land.
The major streams of this region have many tributaries from
the adjacent highlands. Tributaries and main streams alike
provide water for the irrigation of paddy fields along their
courses, and these tributaries and fields are particularly numer-
ous in parts of the western section of the northern depression.
Many of the slopes are occupied by fruit orchards and some
mulberry groves. Much of the floor of the delta plain at the
western end of the depression is in paddy fields.
In the highest part of the depression, and on many of the
adjacent slopes are wide areas of grassland. Other areas in the
depression and many steep slopes which rise from its floor are
covered with evergreen oak forests. The mountainous peninsula
to the southward is forest-covered for the most part, the natural
forests being divided between those of the evergreen oak zone
and of the deciduous forest zone. Probably 1/4 to I. of the area
of the peninsula has an altitude exceeding 1,800 feet, the ap-
proximate altitude at which the evergreen oak forests give
way to the deciduous forests. In addition to the natural forest,
there are large reforested areas. Conifers generally arc planted
in these areas, the cryptomeria being the most popular for this
purpose. The most important deciduous trees are different
species of oak, beech, maple, alder, ash, chestnut, and
cherry, which grows wild through these woods. The conifers
include cryptomeria, pine, fir, cypress, and yew. This region
is one of the most important sources of timber in Japan, and
wood for almost any purpose should be available there. Scattered
throughout the mountains, except in the highest parts, are
small isolated areas of paddy fields or of dry crops, and large
areas of grass and scrubland. More extensive paddy areas oc-
cupy the valley floors along the lower courses of many streams;
at the mouths of some streams are fairly wide delta plains de-
voted to paddy fields. Along most of the peninsula's coast line,
trees border the beach or rocky shore, although fields of rice or
other cultivated crops are not far inland. On the hills of the
small peninsula immediately south of Kainan village, much
land is devoted to fruit orchards.
(2) Kinki Region Lowlands and Highlands.
The Kinki Region is a composite of cultivated basins and
forested upland blocks of irregular shape and arrangement.
Probably more than 1,4 of the area is in cultivated crops, and
some 90 per cent of the cropped area is in paddy fields. These
paddy fields occupy the floors of the basins and some terraces,
wherever water for irrigation can be conducted to the fields
from rivers, ponds, and wells. Throughout the lowlands, various
small raised areas are devoted to dry crops and orchards, the
latter being particularly important. Fruit trees also line many
of the roads and some dikes. The more extensive areas devoted
to dry crops and orchards, however, are the lower slopes of the
hills which border the basins or enclose the many narrow
valleys tributary to the plains.
A fringe of conifers, mainly black pine, lines much of the
Osaka Plain coast south of Osaka. Behind the trees a chain of
tiny villages has been built parallel to the shore. Stretching back
beyond these villages, and filling the spaces between, the rice
paddies occupy most of the plain to the base of the wooded
hills and to the foot of the Tamba Plateau on the north. On
the northeast, the Osaka Plain merges with the KyOto Basin,
the western and northern sides of which abut against the for-
ested slopes descending from the Tamba Plateau. The KyOto
Basin is very much smaller than the Osaka Plain but, like it,
is devoted almost exclusively to rice cultivation. Extensive
stands of bamboo grow along its western margin, bordering the
plateau. Dry crops are less important in this area than farther
south, although much tea is grown along the eastern margin.
Eastward from the Osaka Plain and shut off from it by wooded
ranges of hills is the Nara, or Yamato Basin. The Nara Basin
is another extensive rice area. Because of the good drainage in
a large part of the basin, many paddy fields are planted with
winter crops of wheat, barley, or rape. These crops are harvested
in June, and by the end of that month most of the basin has
been converted into one great flooded rice paddy. It remains so
until November, the rice harvest taking place early in that
month. From November to June the fields that are occupied by
winter crops are relatively dry, and thus do not present the same
difficulty in crossing as do the wet fields. However, they are
built into ridges on which the grain is planted. Moreover, since
the streams flowing into the Nara Basin are subject to floods in
summer and autumn, unusually high dikes and levees?some
as high as 16 feet are built where they will minimize this
danger. Small "islands" of higher land dotted among the rice
fields are frequently planted to fruit trees and thus offer some
concealment. Some of these "islands- are occupied by tree-
studded villages (FIGURE II - 5 1 ). Other sources of limited con-
cealment in this basin are the tree-covered tops of some hun-
dred or more tombs built centuries ago. These tombs are man-
FIGURE II - 51. Ky5to Basin. West Ce.2,tral
Looking E. Trees mark presence of villages in Ky6to Basin, near Uji.
Characteristic of the Nara Basin also. August 1933.
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made hills on the floor of the basin, mainly near the southern
and norther' ends; some are as high as 35 feet, with a length of
more than 350 feet. They usually have a shrine on their sum-
mit, but some may be fortified. The original moats surrounding
them have been turned into paddy fields and the slopes planted
with e'iy cops. A few isolated natural hills have a greater height.
Another outstanding paddy area is on the plain bordering
Biwa-ko (lake). This plain varies greatly in width, being from
2 to 1.5 miles wide along the southeastern and northern shores
and averaging scarcely a mile in -width along the west-
ern side of the lake. In some places it disappears altogether
where steep, wooded hills reach to the water's edge. On Same
el' the moderate slopes dry crops or orchards are grown. Long
fingers of paddy fields, more or less bordered by fields
of dry crops, reach back into the valleys of the streams drain-
ing the northwestern slopes of the Suzuka-sammyaku. In a few
places these paddy areas spread to a width of some 2 miles in
small basins in the mountains. In addition, the Biwa Basin has
many hillside tea gardens, and even more area planted to mul-
berry groves. In some cases these border the roads, but the
latter are more frequently bordered by paddy fields. Tea and
mulberries offer slight obstruction to deployment but give a
small amount of horizontal and oblique concealment. At the
northern end of this range, paddy fields extend well into the
Sekigahara pass, leading from Biwa-ko to Nagoya.
About 2i of the area of the uplands of this region lies beilow
an elevation of 1,600 feet; thus its natural forests are of the
evergreen oak type except where replanting, mostly in conifers,
has taken place. Much cutting has occurred in these forests,
however, and there is little of the original subtropical forest
remaining. Large areas shown as forest: on PLAN 42 are cov-
ered now with scrub pine. Trees of the deciduous forest zone are
found on the uplands above 1,600 feet elevation. A few grass
and scrub areas are scattered through the uplands. There are
more such areas in the south, near the depression separating
this region from that of the Kii-hanth (peninsula).
(3) Ise-wan Lowlands.
With few exceptions, this lowland region encircling Ise-wan
lies below 600 feet elevation. Much of its area consists of
coastal plain, and the rest is of low -roiling hills except for a
narrow range of hills lying immediately west of and almost
parallel to the west arm of the Kiso-gawa (river). This
range, more than 20 miles long, has an elevation above 1,600
feet for some 14 miles and a maximum elevation of about
2,100 feet., The southern end of its higher part is grass-covered
and other large grassy areas appear along the ridge and its
slopes. Elsewhere, except for scrub areas, forests cover the ridge.
Around the base of the ridge the trees are primarily conifers.
Between them and an average elevation of about 1,600 feet is a
belt of the evergreen oak forests. Deciduous forests, interspersed
with the grasslands, occupy the top of the ridge. On a few of the
hills along the northern margin of the region some areas are in
the evergreen oak forests, but most of the forests of the region
(other than those on the range previously described) are coni-
ferous. Broken areas of these forests grow over the low hills
on both sides of Ise-wan, where they are interrupted by the
strips or paddy -fields bordering the many streams flowing
through the hills., Many of the paddy areas are bordered in
turn by mulberry groves and other dry-crop fields. On the west
side of the bay, mulberry groves predominate; on the east side,
other dry crops are of first importance. The northwestern shore
of Ise-wan has a relatively long and wide strip of contiguous
paddy fields. Black pines grow in scattered clumps or thin
broken lines along much of the eastern and western shores of
the bay. At the head of Ise-wan, except for the site of Nagoya
city, the paddy fields arc practically continuous for miles, join-
ing those of the northwestern shore, and reaching northward
beyond the city of Gifu. On the hills to the northeast of the
extensive paddy fields, and interspersed among them to some
extent, are numerous and extensive mulberry groves, and here
and there are areas devoted to dry crops. On the hills to the east,
fruit orchards and mulberry groves occupy considerable areas.
Fruit orchards afford more concealment than do the dry crops
or mulberry groves. Across Chita-wan (bay) from the Chita-
hanto (peninsula) in the southeastern part of the region is an-
other extensive area, roughly 5 by 10 miles, which is devoted
largely to paddy fields. Many mulberry groves, however, are
planted on higher lands among the paddy fields, particularly
in the southern part. At the southeastern corner of this large
expanse of cultivated land is a group of hills, maximum eleva-
tion about 900 feet, covered with conifers. Some of these coni-
fers, however, are mere scrub pine, the original forest presum-
ably having been burned over.
(4) Hainamatsu-Toyohashi Coastal Lowland.
About half the area of this region is under cultivation and
its vegetative cover varies with the seasons. Lands which can
be irrigated are in paddy fields and constitute a larger area than
is in any other crop. Perhaps >l of the paddy area also bears
a winter crop of wheat, barley or legumes. Thus much of the
irrigated land stands bare and muddy from the collected rains
through the winter. From June to September or October a
much larger part is covered with a sheet of water a few inches
deep.
Spread over the lower slopes of many of the hills east of
Hamana-ko ( lake), in some cases over the entire hill, are ex-
tensive tea gardens. Along some slopes these gardens are con-
tiguous for several miles. Usually there are forests higher up
on the slopes, above the tea and covering the tops of the hills.
These forests are almost entirely coniferous, and include much
reforested land. The forests are relatively open, with little
undergrowth. They provide better concealment than the tea
gardens below, and some cover. Although tea occupies a very
large part of the dry crop fields in this region, other dry crops
are grown, particularly vegetables. Fruit orchards and mulberry
groves also occupy considerable areas. Mulberries are grown
in sandy areas not suitable for irrigation; such areas line some
streams. Clumps of bamboo are sometimes found interspersed
with these, but the areas are too small to show on the vegetation
map. The bamboo clumps, which may cover an acre or more,
provide better concealment than the mulberry bushes (provided
they are not too thick to enter), but very inadequate cover.
The lower course of the Tenryii-kawa, as it crosses this region,
is divided into various meandering streams. Most of the large
islands formed between the channels are bare, sandy wastes; a
few are grass-covered, and clumps of trees are found here and
there. The trees are mostly broadleaf?some evergreen, some
deciduous?in contrast to the conifers on the bills. But the
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entire river strip provides practically no concealment or cover.
It is bordered mainly by paddy fields, by dry fields of vegetables,
and by mulberry groves.
West of the Hamana-ko (lake), hills cover a greater part of
the area than east of it, and their forests include many broad-
leaf evergreen trees as well as conifers. Mulberry groves rank
next to paddy fields in area occupied, and there are extensive
groves up the sides of the valley leading from the head of
Atsumi-wan ( bay ). Many smaller areas of mulberry spread
over the .Atsumi-hanto (peninsula), bordering the paddy fields
along the streams. A wide strip of mixed pine forest, scrub pine,
and grass, borders the western sandy shore of the peninsula
and spreads irregularly over the hills along the middle of the
peninsula. Fields, mainly of mulberries and vegetables, skirt
almost the entire northern and southern shores of the penin-
sula, but in some parts a strip of trees, some deciduous, some
coniferous, intervene between the sandy beach and the cropped
land.
Most of the coast east of the Atsumi-hanto ( peninsula ) is
sandy, with some grass cover. In the extreme cast, dunes appar-
ently have been reclaimed and planted to vegetables.
(5) Central Honshu Rugged Highlands.
The hills and mountains of this region are covered for the
most part with mixed forests. In the lower part of this forest
the most conspicuous coniferous trees are the cryptomeria,
cypress, and yew; at higher altitudes the firs predominate, then
the larches appear. The deciduous trees include the oaks,
beeches, maples, alders, ashes, and chestnuts. There are some
broadleaf evergreen species at low elevations. Some of the high
mountains, reaching 7,000 to 10,000 feet elevation, have con-
siderable bare rock at their summits surrounded by an alpine
flora typical of high mountains. Near the top grow some species
of alder, willow and other shrubs. Upper edges of the forest
are frequently bordered by a dwarf pine.
Many areas of grass and scrub, ranging from those too small
to show to areas of many square miles, are scattered over the
mountain. These are almost invariably found on relatively
steep slopes. Some extensive areas of bamboo, as well as small
clumps, grow in these mountains. The scrubland is most widely
distributed over mountainsides between about l ,300 and 2,300
feet.
Strips of paddy fields are strung along the water courses at
the bottoms of the narrow valleys, or on terraces. On many
cultivable areas which irrigation cannot reach, dry crops and
mulberry groves are planted. There is only 1 sizable area of
land under cultivation. This is the long, narrow, steep-walled
richt Valley, which is a section of the upper valley of the Tenryii-
kawa, and occupies the extreme northeastern part of the region.
Rice paddies cover the valley floor, but between the 2 main
belts of paddies in the northern part lies a belt of mulberry
groves. Farther down the valley the division of land between
the 2 crops is very irregular as the surface is less uniform.
In some places the paddy fields extend from the steep slopes of
one enclosing wall to the other; in other places the mulberry
groves do practically the same thing. In parts of the valley
gentle slopes intervene between the valley floor and the steep
sides of the towering ranges on either side. The greater part of
these slopes supports mulberry groves and, except for the rela-
tively small area planted to dry crops, the remainder is occupied
by coniferous forests. Small patches of forest, mostly coniferous,
are scattered through the valley. These few trees and the dis-
connected woods on the foothills provide the only concealment
throughout the length of the valley, except for the limited
amount which the mulberry bushes afford foot troops.
The narrow coastal plain bordering part of the Tsuruga-wan
( bay), where this region meets that arm of the Japan Sea, is
planted mainly to dry crops. These crops afford little or no
concealment and no cover. Back of the strip of coastal plain
are the forest-covered hills.
G. Distribution of vegetation in Western Honshu.
( 1) Tamba Broken Plateau.
The very irregular surface of this region is covered primar-
ily with forests. Most of the region has an altitude less than
2,000 feet; the native forests, therefore, are of the evergreen
oak type, except in the northern part facing the Japan Sea.
There the deciduous forests, interspersed with pure stands of
conifer, cover the hills to their base at sea level. Scattered
through the uplands, particularly in the west and northwest,
are many areas of grassland and scrub. The bushes of the
scrub provide a small amount of concealment, but neither grass-
land nor scrub offers cover.
A number of river valleys are relatively open, with irrigable
plains several square miles in area. These plains are devoted to
paddy fields. The valley of the Sonobe-kawa, in the southeast,
has the greatest extent of paddy field area. Mulberry groves,
providing limited concealment, occupy unirrigable land bor-
dering the course of the Yura-gawa, the Marugawa-kawa, and
the Sonobe-gawa, for several miles in each valley. Some other
river bottomlands and some hillsides support groves to a lesser
extent. Areas of fruit orchards and dry crops are found in
many valleys, but are usually small and isolated. A concentra-
tion of chestnut orchards on terraced hillsides is found in the
southwestern part of the region. Bamboo groves or bare sandy
stretches frequently adjoin the mulberry groves of the river
banks.
(2) Matsue-Tottori Coastal Lowlands.
Hills, wooded for the most part, but partly grass-covered,
fringe the coastal plain on the south. The surface of the low-
land is irregular and cannot all be cultivated. In some parts
the forests reach the shore. These forests consist of deciduous
and coniferous trees. About Y3 of the plain is in paddy fields,
and approximately half as much land is in mulberry. Mulberry
groves occupy hill slopes and river levee banks; the areas most
intensively devoted to this crop are the beach ridges on the
sand spit at the eastern end of Nakano-umi. Throughout this
peninsula there are rows of mulberry groves interspersed with
narrow strips of paddy fields, dry crops, and clumps of bamboo.
A narrow strip of grass borders the sandy beach on the north-
eastern shore; inland is an irregular belt of pines, behind which
are fields. The groves and dry fields of this peninsula offer
firm ground for wheeled vehicles. Daikon-shima is also cov-
ered with mulberry groves behind a narrow border of paddy
fields.
Most of the land behind the Shinji range is irrigable and is
in paddy fields. Forests are found along parts of the shores of
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both Nakano-umi and Shinji-ko. 'The plain west of Shinii-ko
is essentially one expanse of paddy fields, except at its western
end where a belt of low hills skirts the shore. These hills are
covered mostly with mulberry, orchards, and some vegetables
and grain. A fringe of pine borders the beach, and pines are
also scattered in the hills.. Throughout this region the farm-
steads are protected on their north and west sides by wind-
breaks of trees 20 to-50 feet high, trimmed square on top. Each
farmstead appears to be a small grove of trees (FIGURE II - 152).
These windbreaks provide considerable concealment.
The Shinji range has many irrigable valleys with ribbons of
paddy fields bordering the streams. Scant area is devoted to dry
crops; forests, grass and scrub cover the hills and steep slopes..
There is only a little land under cultivation on the seaward
side of the range.
FIGURE II - 52. Matsue-Tottori Lowlands, Western Honshu.
Looking SW. Windbreaks protect farmsteads near Matsue. Water
shows between rows of young rice. Rows of beans
mark the dikes. 11 July, 1931.
( 3 ) -Western Honshu Rugged Highlands.
The highlands of Western Honshu extend westward from
the Tamba Plateau to the Shimonoseki-kaikyO. The greater
parr of the region is forested, but there are many wide expanses
of grassland. A larger part of this area, is grass-covered than any
other region of Southwest Japan. There is also much cut-over
and. wasteland. Deciduous forests occupy most of the lower
elevations and coniferous the higher land, except for the large
grass area.. The grass is not suitable for fodder, although there
are a greater number of cattle in this region than elsewhere
in Southwest Japan. Numerous valleys criss-cross the irregular
highlands, and are occupied by strips of paddy rice. Dry crops
border some of the paddy areas, and are also found around
many of the villages.
( 4 ) Western Honshu Broken Lands.
The Western Honshu Broken Lands are composed of the
series of small coastal plains along the Inland Sea from Himeji
to Shimonoseki. The low hills which separate these plains are
included, together with the lower slopes of the Western Honshu
Rugged Highlands. Paddy fields cover the irrigable parts of
the small plains and valleys leading into the hills. Rice is found
also on terraced hillsides. The largest of the paddy areas along
the -western part of the coast are on the deltas of the Fushino-
gawa and the Saba-gawa. In the eastern part the most exten-
sive paddy area borders 2 sides of Kojima-wan (bay), surrounds
the city of Okayama, and extends long arms to the north, west,
and east. The delta and valley of the Ashida-kawa, some 30
miles west of Kojima-wan, also have considerable paddy area.
A part of the irrigable land along the margin of the Inland
Sea is used for growing a reed crop, called "I", used for making
floor matting. In the northern part of the eastern plateau there
is a series of broad, open valleys whose irrigable floors are
devoted to paddy fields.
Many terraces and slopes are planted to various dry crops
and to fruit orchards. Some of these are on hills overlooking
the Inland Sea; others face each other across the valleys. Mul-
berry groves and other dry crops are planted here and there on
the levees of the streams and on small raised "islands" among
paddy fields. In the extreme eastern part of the region, tea
gardens occupy a small part of the cultivated land.
By far the greater part of the region is covered with forests,
either natural or planted, but there are also many areas of
grassland and scrub. Individual grasslands are not extensive,
and the grass is of little value as fodder.
The natural forests of this region have been replaced largely
by deciduous-broadleaf and coniferous species. Practically all of
the plantings are coniferous, mainly cryptomeria. There are
relatively large areas of scrub pine, particularly south of Ko-
jima-wan. The hills south of Hiroshima are an important source
of timber, and are more accessible than those of the interior.
Most of the coast is backed by tree-covered hills. Clumps of
bamboo are found at intervals along many streams.
The vegetation on the islands of the Inland Sea which are
included in this region is similar to that found on the mainland.
(5) Himeji-Yashiro Lowland.
This is the coastal region of Honshu between Akashi and
Himeji. This region is low, and practically all of it within 5
miles of the coast is in flooded fields. Occasional hilltops rise
above 700 feet and are forested. The evergreen oak forest zone
includes this region, but the natural forests of this type have
been much depleted by cutting and fire, being replaced by oak,
beech, alder and sumac. Conifers predominate, however, in most
of the region, and include various species of pine, fir, cedar,
cryptomeria, and cypress. Some of these have been planted.
Patches of grass and bamboo are found along streams and in
the forests.
Some of the rice fields reach the edge of the sea. The paddy
area is divided by low hills, extensions of the higher hills to
the north. In the valleys of the Ichi-kawa and the Kako-gawa
paddy fields extend almost continuously across the region.
Other paddies form a series of flooded areas in the broad basins
between the hills which extend across the center of the region
from east to west. Seemingly countless small streams are lined
with paddy fields in this Himeji-Yashiro Lowland. Some of
the slopes and terraces, dikes and levees along the larger streams
are planted to dry crops, wheat or barley in winter and vegeta-
bles in summer. Many of the rice fields are planted to grains in
the winter.
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25. Regional Summary
The relief, drainage, and vegetation of Southwest Japan are summarized by terrain regions in Table II - 1 below.
TABLE II - 1.
REGION
Kynshil
( I) Southern Kyushu
Lowlands and
Highlands
(2) Central Kyushu
Mountains.
(3) Northern KyCishfi
Lowlands and
Highlands.
(I) Northwest Kyfishfi
Broken Lands.
Shikoku
(1) Southwestern
Shikoku
Broken Lands.
(2) Central Shikoku
Mountains.
(3) Kochi Plain.
RELIEF
Three coastal lowland areas among rugged
uplands of moderate height; narrow pass-
ageways between lowlands; some rice on
larger lowlands. Deployment and cross-
country movement is fair in lowlands,
poor in passageways, very poor in up-
lands.
Southern highland belt has rugged blocks
with scattered higher volcanoes, narrow
deep valleys, few passageways; rice in
most valleys. Northern highland arm does
not reach coast; has lower blocks and
peaks, some hills, wider valleys, a few
narrow valley routes. In both areas de-
ployment almost impossible, cross-country
movement very difficult.
Low rugged mountain areas rimmed by
hills and separated by flattish lowlands
which face enclosed bays. Narrow corri-
dors connect lowlands; many heights dom-
inate corridors; rice fields on lowlands.
Deployment and cross-country movement
possible on lowlands, restricted in corri-
dors, difficult in uplands.
Series of long narrow irregular peninsulas
and offshore islands; rugged hills and low
mountains; few high volcanoes; narrow
winding valleys; no corridors; some rice
in valleys. Deployment and cross-country
movement difficult.
Rugged mountains, moderate heights;
many long, narrow, deep, winding, valleys
form fair passageways, are not corridors;
rice fields in most valleys. Deployment
and cross-country movement very difficult.
Rugged, steep, 3500-6000 ft. ridges; long
deep, narrow, valleys; winding streams
and some rice fields in valleys; no low
passes; no corridors. Deployment and.
cross-country movement very difficult.
Small coastal plain where several valleys
converge; largest clear flat areas 6 by 8
miles; rice fields on flats; ridges between
valleys form commanding heights. De-
ployment and cross-country movement
possible.
DRAINAGE
Highlands: Stream gradients steep, with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams; dan-
ger of flash floods even on basin flats.
Lowlands: Streams elevated slightly;
dikes common; barren flats exposed be-
tween dikes and stream at low water;
muddy banks and bottom unusual; streams
canalized in urban areas; numerous irri-
gation ponds and canals on many larger
lowlands; natural swamps rare; rice field
swamps in all lowlands.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power clams; dan-
ger of flash floods even on basin flats.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power clams; dan-
ger of flash floods even on basin flats.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams can-
alized in urban areas; numerous irriga-
tion ponds and canals on many larger
lowlands; natural swamps rare; rice field
swamps in all lowlands.
Highlands: Stream gradient steep with
many fills and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams; dan-
ger of flash floods even on basin flats.
highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
PREDOMINANT VEGETATION
Rice on irrigable lowlands and narrow
valley floors. Mulberry groves, fruit orch-
ards, and other dry crops on many lower
slopes. Forests, broadleaf evergreen and
coniferous, cover most of uplands. Patches
of grassland and scrub scattered through
forests.
Rice on coastal plains and narrow strips
along streams. Dry crops on lower slopes
above rice. Grasslands and scrub occupy
wide belt across northern part of region;
scattered patches elsewhere. Forests cover
most of region; deciduous and coniferous
trees above about 2800 feet; broadleaf
evergreen and coniferous trees lower
down.
Much rice on Saga and lesser plains.
Terraced paddy fields bordering Saga
Plain. Dry crops on hillsides, especially
northeast of Kumamoto. Grass on western
uplands, and scattered patches elsewhere.
Broadleaf and coniferous forests on other
uplands. Less forest area, proportionately,
in this region than in most regions.
Narrow strips of paddy fields along
streams. Dry crops on many slopes in
southeast. Grass over wide areas in west
and north. Forests over most of region;
broadleaf evergreen and coniferous ex-
cept in high elevations; deciduous and
coniferous there.
Most of region covered with broadleaf
evergreen and coniferous forests. Camphor
trees relatively numerous in Tosa-wan
area. Grass and scrub patches mainly in
northeast. Paddy fields in strips along
streams. Dry-crop fields, many mulberry
groves, on slopes of northwest and west.
Orchards on south coastal and valley
slopes.
Forests, conifers with deciduous trees in
high mountains and broadleaf evergreen
over most of region. Extensive grass and
scrub areas in west, lesser ones in east.
Paddy areas few; mostly in valleys of ex-
treme northwest and tributary to cast
coast. Dry crops on many interior slopes.
Paper mulberry in southwest.
Extensive paddy fields over most of low-
lands; two crops annually. Mulberry im-
portant dry crop of low slopes and grav-
elly borders of streams. Broadleaf ever-
green forests on hills and unirrigable low-
lands.
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REGION
( ) Eastern Shi koku
Lowland s.
(5) Northern Shikoku
Lowlands.
West Central Honshit
(I Kii-hanto
Mountain Land.
Kinki Region
Low lands and
Highlands.
( 3 [se-wan Lowlands.
(4) Hamamatsu-
Toyohashi
Coastal Lc wlands.
5) Central Honshu
TA BLE
RELIEF
Narrow wedge-shaped lowland and coast
strip; low flat-topped terraces in wedge;
small flat deltas on coast; much rice; all
exits over high ridges; comanding heights
on ridges. Deployment and cross-country
movement possible.
Series of lowlands along coast for 130
miles; narrow, flat connections between
most lowlands; scattered hills on lowlands
and on rugged highland rim form com-
manding heights; rice fields on lowlands.
Deployment and cross-country movement
possible.
Large triangular peninsula; high rugged
mountains; narrow winding valleys with
many commanding heights; no corridors;
two small coastal lowlands; rice in low-
lands and some valleys. Deployment and
cross-country movement very difficult in
mountains, possible in small lowlands.
Four large flat-floored basins separated by
low steep-sided ridges; higher blocks and
ridges along eastern boundary; many pas-
sageways and a few good corridors be-
tween basins; long narrow valleys and
one short passageway through eastern
highlands; commanding heights above all
passageways and corridors. Deployment
and cross-country movement possible in
basins and corridors, difficult in passage-
ways, very difficult on ridges.
Large horseshoe-shaped lowland around
bay: marginal terraces and rugged hills
on east and west; square 24- by 32-mile
Nagoya Plain on north; rice on plain and
in small valleys among hills. Deployment
and cross-country movement is possible on
plain and in valleys, moderately difficult
in hill and terrace areas.
Long, narrow coastal lowland; series of
river plains separated by large high ter-
races and rugged hilly areas; hills and
terrace margins form commanding
heights. Much rice on plains and between
hills. Deployment and cross-country move-
ment possible on river plains and terrace
flats; difficult on terrace margins and
hills.
High rugged mountain ranges on the east;
Rugged Highlands. rugged ranges and dissected blocks of
lesser height on west; long, narrow, wind-
ing, deep, valleys and narrow basins;
many commanding heights. Rice in basins
and in few sections of valleys. Deploy-
ment and cross-country movement difficult
in valleys and basins; very difficult in
highlands.
trestera Iloesh
( 1) Tarriba Broken
Plateau.
Low but steep-sided -blocks and ridges,
separated by long narrow valleys and in-
terior basins which form passageways but
not true corridors; many commanding
heights above passageways. Rice fields in
many valleys. Deployment and cross-
country possible in valleys, very difficult
in highlands.
- I (Continued)
DRAINAGE
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
hanks and bottom unusual: streams canal-
zed in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds anti canals on many larger low-
lands; natural swamps tare; rice field
swamps in all lowlands.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin fiats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin fiats.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
Lou-lands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Lou-lands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
PREDOMINANT VEGETATION
Paddy fields cover more than half of re-
gion. Dry crops, chiefly mulberry, on
higher lands along river and on delta.
Forests, mainly conifers, on the few hills.
Paddy fields cover greater part of region,
2/3 also used for winter grain or vege-
tables. Mulberry, fruit, and vegetables on
lower slopes and unirrigable lowla.nds.
Conifers, broadleaf evergreens, and
grassy patches on hills.
Forests cover most of region; coniferous
and broadleaf deciduous on highest parts,
coniferous and broadleaf evergreen at
lower elevations. Paddy fields on irrigable
land of lowlands, and in strips along
some valleys and small deltas. Fruit orch-
ards and other dry crops on south-facing
hills of one small lowland.
Paddy fields on irrigable parts of basins,
narrow valleys, and terraces. Dry crops on
small, raised "islands" in paddy areas,
and on hillsides above paddy fields. fruit
orchards, flowering trees numerous. Tea
on some slopes in basins. Forests cover
uplands and most slopes; coniferous and
broadleaf deciduous widespread. Small
areas of grass and scrub scattered through
forests.
Paddy fields cover the irrigable coastal
plains and many narrow valleys. Dry
crops on unirrigable lowlands and lower
slopes. Mulberries on -islands" of plain
and eastern and western hills. Fruit orch-
ards on hills in east part. Forests on
higher hills and upland rim. Grass patches
scattered through forests.
Paddy fields on irrigable lowlands. Winter
grain and legumes on 1/3 of paddy area.
Tea gardens on many terrace slopes in
eastern part of region. Mulberries pre-
dominant on lower slopes of hills in
western part. Other dry crops on some
slopes. Open, coniferous forest on terraces
and hills above tea. and mulberries.
Forests cover large part of region; mostly
conifers and mixed broadleaf deciduous;
broadleaf evergreen at low elevations;
alpine flora on some high mountain tops,
other tops bare. Grass and scrub areas
usually on very steep slopes. Paddy fields
on irrigable parts of lida Valley; in nar-
row strips along other streams. Dry crops
on slopes above these strips. Mulberries
on unirrigable parts of Iida Valley and
on bordering low slopes.
Forests, mixed coniferous apd deciduous,
on hills bordering Japan Sea. Mixed
broadleaf (mainly evergreen) and coni-
ferous over most of region. Much scat-
tered grass and scrub. Strips of paddy
fields along many streams. Mulberry
groves on unirrigable borders of streams
in northwest. Small areas of fruit orchards
and dry crops on scattered slopes.
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REGION
(2) Matsue-Tottori
Coastal Lowlands.
(3) Western Honshu
Rugged Highlands.
(4) Western Honshfi
Broken Lands.
(5) Himeji-Yashiro
Lowland.
TABLE II - I (Continued)
RELIEF
Series of small deltas and one large sand
spit; some deltas are connected by narrow
coastal flats. Lakes and rock ridges sep-
arate larger flat areas. Many rice fields.
No corridors or easy passageways inland.
Commanding heights above most of deltas
and all coastal flats. Deployment and
cross-country movement possible on deltas
and sand spit, difficult elsewhere.
Rugged ridges and flat-topped blocks
with steep sides; these decline in west to
form rugged hills; many long narrow
valleys; no corridors; commanding heights
above all valleys; rice in larger valleys.
Rugged highland blocks and isolated
ridges separated by nets of narrow valleys
and basins. Several small hill-dotted
coastal plains with tributary valley nets;
commanding heights above all valleys and
most plains. Rice in coastal uplands and
in larger valleys. Deployment and cross-
country movement possible on coastal
plains; difficult in uplands.
Small irregular hill-dotted coastal low-
land with tributary valley net penetrating
Tamba Plateau to north. Commanding
heights above valleys and most of plain.
Much rice in coastal plain and larger val-
leys. Deployment and cross-country move-
ment possible in plain, difficult in valleys
and on hills.
26. Natural Critical Areas
DRAINAGE
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
Highlands: Stream gradient steep with
many falls and rapids except in scattered
tiny basin flats; streams fill narrow valleys
and meander from side to side in basins;
some water storage and power dams;
danger of flash floods even on basin flats.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
Lowlands: Streams elevated slightly; dikes
common; barren flats exposed between
dikes and stream at low water; muddy
banks and bottom unusual; streams canal-
ized in urban areas; numerous irrigation
ponds and canals on many larger low-
lands; natural swamps rare; rice field
swamps in all lowlands.
There are 2 natural critical areas in Southwest Japan:
Northern Kyushu, and the Kinki Basins Region of Central
Honshu..
The Northern Kyushu critical area, at the western end of the
Inland Sea, includes a great industrial zone. Together with the
southwestern tip of Honshu it controls Shimonoseki-kaikyO,
one of the entrances to the Inland Sea. In large measure it also
controls the Tsushima-kaikyO and Chosen-kaikyo. It is the near-
est to the continent of Asia of any of Japan's important areas.
The second natural critical area is the Kinki Basins Region
at the eastern end of the Inland Sea. Here a group of 5 low-
lands-2 coastal: Osaka and Nagoya; and 3 interior: Nara,
Kyoto, and Biwa?combine several factors of importance. The
Osaka Plain is highly industrialized. Kyoto and Nara are
cultural and historical centers of national significance, and
KyOto contains some industry. The Biwa Basin has a large
fresh-water lake and is a key point of important trans-island
routes. Nagoya is industrialized, and its surrounding lowland
is the most exposed to amphibious attack of any of the large
plains of Southwest Japan. The Kinki Basins, as a group, con-
tain the largest extent of flat land in Southwest Japan. Even
though these lowlands are separated by mountain and hill bar-
riers, there is room for the construction of airfields and base
facilities.
PREDOMINANT VEGETATION
Paddy fields on irrigable lowlands. Dry
crops, largely mulberry, on unirrigable
lowlands and lower slopes. Forests, decid-
uous and coniferous, on hills. Windbreaks
of trees protect farmsteads. Scant grass
areas.
Forests cover most of region: coniferous
and deciduous along Japan Sea north of
about 34? 30' N, and at high elevations;
coniferous and various broadleaf mixed
elsewhere. Extensive areas of coarse grass
and scrub in eastern and western thirds
of region. Strips of paddy fields along
many streams. Dry crops on slopes around
villages.
Paddy fields on coastal lowlands and in
valleys, also on lower slopes above some
valleys. Cultivated reeds in some flooded
fields. Dry crops on many slopes, river
levees, and "islands" in paddy areas. Thin
forest of coniferous and mixed broadleaf
covers uplands between valleys.
Paddy fields cover extensive areas near
coast and in basins behind low hills. Dry
crops on some slopes. Forests, mainly
conifers (partly scrub pine), including
deciduous and evergreen broadleaf, cover
hills and unirrigable lowlands.
27. Routes to Natural Critical Areas
There are many routes to the critical areas of Japan, but
few of them are really good natural passageways. Forty-six of
the possible routes leading toward the principal objectives of
Southwest Japan have been selected for detailed treatment.
There are many others. The location of the routes is shown
on FIGURE II - 53 and on PLANS 39 and 40. On the plans, the
routes can be assessed in relation to the topography they cross
A. General.
The greater part of all routes in Southwestern Japan are in
rugged hill and mountain country. Within such terrain, routes
are confined to valleys and small basins which are separated at
drainage divides by high steep ridges.
Most of the valleys are deep, narrow, and winding. Valley
floors, where flat or gently sloping, are covered with muddy
rice fields or with dry crops. Farmsteads and compactly built
farm hamlets cling to the lower slopes. Steep, forested slopes
rise 200 to 2,000 feet on either side and provide commanding
heights for almost all sections of the routes.
Shallow, but swift, mountain streams completely fill the
narrower sections of most valleys, and meander from side to side
of the wider parts. These streams are subject to sudden flash
floods during summer and early autumn ( June to mid-Sep-
tember).
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Page II - 42 MILITARY GEOGRAPHY
Because of the various handicaps to mobile operations
within the mountain sections of the routes, deployment off the
route is extremely difficult. Cross-country movement is equally
difficult. Established lines of communication along the routes
are forced to use many bridges, cuts, fills, and sharp turns, in
order to get through. Railways have numerous tunnels.
Those sections of routes which lie in the larger basins and
small coastal plains of Southwest Japan have easier grades,
and there is room for deployment off the routes, but if bridges
and roadways are destroyed, both deployment and cross-country
movement become difficult. Chief handicaps are muddy rice
fields., numerous streams, irrigation ditches and ponds, and a
large number of small but compactly built farm hamlets at
to I mile intervals. On many of the larger plains, major streams
flow between levee walls 20 to 40 feet high. Stream levels are
frequently high enough to cause local flooding by breaking
the levees. Flash floods from heavy rains are also to be ex-
pected on the lowlands during summer and autumn ( :luly
through September).
Many plains and almost all the basins and large valleys have
marginal highlands and outlying hills and ridges which pro-
vide commanding heights above the lowland routes.
B. Description of individual routes.
The individual routes are described on FIGURES II - 54
through II - 106. These routes lead from either the Pacific
Ocean, East China Sea, or the Japan Sea to the 2 critical areas
of Southwest Japan, or to localities which contribute to their
defense, such as .Kii-suidO, Bungo-suidO, Shimonoseki-kaikya,
Hiroshima and Kure, and Okayama.
Thc selection of the routes is somewhat arbitrary, and is
based fundamentally on natural geographic factors of ease of
movement overland, and secondarily on the presence of estab-
lished transportation routes. All of the possible routes are not
included, but most of the usable natural routes are described.
Additional routes are discussed in CHAPTER VII.
The detailed route studies below are arranged with an arbi-
trarily selected start and finish. Branching and connecting routes
are similarly arranged. Any combination of routes that join
each other may be used, and movement of troops in either
direction may be planned.
For the purpose of the route studies, areas which are pre-
dominantly in rice have been classified as favorable for deploy-
ment even though wheeled vehicles will undoubtedly bog in
such areas during most seasons.
28. Principal Sources
I. Bogush.vski, N. P.
1904. YAPONIYA, VOYENNOGEOGRAFISCHESKOYE OBOZRENIYE.
(Military Geography of Japan). In Russian. 307 pp., 1 -map.
St. 13,tersburg.
2. Cushing, S. W.
1913. COASTAL PLAINS AND BLOCK MOUNTAINS IN JAPAN.
Annals of the Association of American Geographers. Vol. 3,
pp. 33-6i. 2 maps, 5 diagrams.
3. Hall, Robert B.
193 SOME RURAL SETTLEMENT FORMS IN JAPAN. Geograph-
ical Review, Vol. 21, No. I, pp. 93-123, illus. New York.
* 4.
1932. THE YAMATO BASIN, JAPAN. Ann. Assn. Am. Geog., VOL
22, pp. 211-230. 14 maps, 3 diagrams, 2 profile sketches,
5 tables.
* 5. Hall, R. B. and Watanabe, A.
1932-1933. LANDFORMS OF JAPAN. Reprint from Papers of the
Michigan Academy of Science, Arts, and Letters. Vol. 28. 51
pp., 5 maps, 6 plates. Ann Arbor.
6. Hall, Robert B.
1934. THE HIINTOKAWA PLAIN, Proceedings of the Fifth Pacific
Science Congress, Victoria and Vancouver. 1933. Vol. 2, pp.
1359-71. 13 maps, 3 photographs, 7 diagrams, I table. Toronto,
Univ. of Toronto Press.
7.
1934. THE CITIES OF JAPAN: NOTES ON DISTRIBUTION AND
INHERITED FORMS. Ann. Assn. Am. Geog., Vol. 24, pp. 175-
200. 12 maps, 2 photographs.
8.
1937. TOKAIDO: ROAD AND REGION. Geog. Rev. Vol. 27, pp.
353-77. 10 maps, 14 photographs, 2 diagrams. New York.
* 9. Japan, Department of Communications, Bureau of Electric Power.
1933. SUMMARY OF RIVER DISCHARGE, 1920-1929. In Japanese,
530 pp., 5 pages of diagrams, 1 map. Tokyo.
410. Lehmann, F. W. Paul.
1922. MORPHOLOGISCHES LIEBER DIE 1NLANDSEE JAPANS (Mor-
phological Remarks on the Inland Sea of Japan). Petermanns
Mitteilungen, Vol. 68, pp. 218-219. Map.
11. Nakamura, Shintaro.
1934. MOUNTAIN GRAVELS IN THE SHIGARAKI PLATEAU, CEN-
TRAL JAPAN. Proceedings of the Fifth Pacific Science Congress,
Canada, 1933, 1934. Vol. 2, pp. 1593-1596. Toronto.
12. Rein, J. J.
1880. DER NAKASENDO IN JAPAN. (The Nakasendo is an inland
mountain road between Kyoto and Tokyo). Petermanns Mit-
teilungen; Ergaenzungsheft (Supplement) No. 59. In German.
pp. 1-35. 3 maps.
13. Scheidl, Leopold G.
1937. DER BODEN JAPANS (The Soil of Japan). Deutsch Gesell-
schaft fiir Natur und Volkerkunde Ostasiens Mitteilungen,
No. 30, Pt. A, 30 pp., soil map.
14. Toki, R.
1929. PHYSIOGRAPHEC DEVELOPMENT OF THE SOUTHERN PART
OF SUHO-NADA. Geog. Rev. of Japan, Vol. 5, No. 1. Tokyo.
*15. Trewartha, Glenn T.
1928. A GEOGRAPHIC STUDY OF SHIZUOKA PREFECITIRE,
JAPAN. Ann. Assn. Am. Geog., Vol. 18, pp. 127-259, 14 maps,
41 photographs, 1 diagram, 2 tables.
*16. ---.
1934. A RECONNAISSANCE GEOGRAPHY OF JAPAN. University
of Wisconsin Studies in the Social Sciences and History, No.
22. 21 tables, 54 maps and sketches, 49 photographs, 283 pp.,
including plates. Madison.
17. Tsujimura, T. and Kawada, S.
1930. CRUSTAL MOVEMENTS OF THE Isti PENINSULA CONSID-
ERED FROM THE ALTITUDE DISTRIBUTION OF COASTAL TER-
RACES. Geog. Rev. of Japan. In Japanese. Vol. 6, pp. 1754-
1767. Tokyo.
18. U. S. War Department, Headquarters Army Air Forces, Weather
Division.
1943. SOIL TRAFFICABILITY IN MILITARY OPERATIONS. Publi-
cation No. 347, revised. 25 pp., illus. (Restricted).
'19. U. S. War Department, Office Chief of Engineers, Intelligence
Branch, Military Geology Unit.
Unpublished manuscripts, maps, imd data on Japan. (Con-
fidential).
20. Watanabe, Akira.
1929. ON THE ELEVATED DELTAS OE JAPAN. Geographical Re-
view of Japan. In Japanese. Vol. 5, No. I, pp. 1-15; 1 map.
Tokyo.
Approved For Release 2004/12/20 : CIA-RDP79-01144A001500010002-3
Approved For Release 2004/12/20 : CIA-RDP79-01144A001500010002-3
foe entegra" MILITARY GEOGRAPHY
21. Yabe, Hisakatsu.
1934. SUMMARY OF THE PAPERS ON THE PHYSIOGRAPHY OF THE
JAPANESE ISLANDS. Proceedings of the Fifth Pacific Science
Congress, Victoria and Vancouver 1933, Vol. 2, pp. 1573-1575.
Toronto, Univ. of Toronto Press.
22. Yamasaki, N.
1902. MORPHOLOGISCHE BETRACHTUNG DES JAPANISCHEN
I3INNENMEERS SETOUCHI (Morphologic Study of the Japan-
ese Inland Sea). Petermanns Mitteilungen. In German. Vol.
48, pp. 245-253, 1 map.
23. Yamasaki, N. and Sato, T.
1903-1915. THE REGIONAL GEOGRAPHY OF JAPAN. In Japan-
ese. 10 vols., maps, photographs.
Basic sources.
MAPS AND CHARTS
24. Hayakawa, G. and Fesca, M., Japan, Imperial Geological Survey.
1894. AGRONOMIC MAP OF WAKASA AND ECHIZEN PROVINCES.
Scale 1:100,000.
25. Japan, Imperial Land Survey Department ( Japanese General Staff ) .
1897-1940. JAPANESE EMPIRE. Scale 1:50,000.
26.
1890-1939. JAPANESE EMPIRE. Scale 1:200,000.
27. Japan, Imperial Geological Survey.
1891-1921. JAPANESE EMPIRE. Scale 1 : 200,000.
28. Japan, Imperial Geological Survey, Ministry of Agriculture and
Commerce.
1903. A SURVEY OF THE SOILS OF JAPAN WITH A GEOLOGICAL
Page 11 - 3
MAP OF JAPAN. Scale of soil maps, 1:50,000; scale of geologic
maps, I : 1,000,000.
29. Kamoshita, M. and Fesca, M., Japan, Imperial Geological Survey.
1893. AGRONOMIC MAP OF OMI PROVINCE. Scale 1:1,000,000.
30. Kobayashi, F. and Fesca, M., Japan, Imperial Geographic Survey.
1893. AGRONOMIC MAP OF IKE AND TSUSHIMA PROVINCES AND
THE SOUTHWESTERN PART OF HIZEN. Scale 1:100,000.
31. Matsuoka, M. and Fesca, M., Japan, Imperial Geological Survey.
1899. AGRONOMIC MAP OF KAWACHI AND KOMI PROVINCES
AND THE EASTERN PART OF SErisu. Scale 1:100,000.
32. Minari, B. and Tsuneto, N., Japan, Imperial Geological Survey.
1897. AGRONOMIC MAP OF KYUGO PROVINCE. Scale 1:100,000.
33. Minari, B., Kobayashi, B. and Susuki, J., Japan, Imperial Geologi-
cal Survey.
1899. AGRONOMIC -AP OF ETCHU PROVINCE. Scale 1:100,000.
34. Seki, T., Tokyo Imperial Agriculture Experiment Station.
1930. OUTLINE SOIL MAP OF JAPAN. Scale 1:5,000,000.
35. U. S. War Department, Army Map Service.
1943. 5301, EASTERN ASIA. Ed. 2. Scale 1:1,000,000.
36.
1943-1944. L571 CENTRAL JAPAN. Scale 1:250,000.
OTHER SOURCES
In addition to the sources cited, persons with detailed knowledge of
the area were consulted and aerial photographs and intelligence reports
were used.
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Approved For Release 2004/12/20 : CIA-RDP79-01144A001500010002-3
TABLE OF CONTENTS
Page
24. VEGETATION 11 -26
A. General II -26
B. Description of uncultivated vegetation types . . II-28
(1) Broadleaf evergreen forest II - 28
(2) Coniferous forest II - 28
(3) Broadleaf deciduous forest II - 29
(4) Mixed forest 11 -29
(5) Wasteland, scrubland, and grassland II -29
C. Description of cultivated vegetation types II - 29
(1) Paddy rice 11 -29
(2) Dry-field crops II - 30
(3) Orchards II - 30
(4) Mulberry II - 31
(5) Tea II - 31
D. Distribution of vegetation by terrain regions: Kytishii II - 31
(1) Southern Kyfishil Lowlands and Highlands . . II - 31
(2) Central Kyfishil Mountains II - 32
(3) Northern Kyushu Lowlands and Highlands II -33
(4) Northwestern Kyushu Broken Lands II- 33
E. Distribution of vegetation in Shikoku II- 33
(1) Southwestern Shikoku Broken Lands II - 33
(2) Central Shikoku Mountains II-34
(Continued)
Page
(3) KOchi Plain II - 34
(4) Eastern Shikoku Plain II - 34
(5) Northern Shikoku Lowlands II - 34
F. Distribution of vegetation in West Central Honshu II - 35
(1) Kii-hantO Mountain Land II - 35
(2) Kinki Region Lowlands and Highlands . II - 35
(3) Ise-wan Lowlands II - 36
(4) Hamamatsu-Toyohashi Coastal Lowland II - 36
(5) Central Honshu Rugged Highlands II - 37
G. Distribution of vegetation in Western Honshu II - 37
(1) Tamba Broken Plateau II - 37
(2) Matsue-Tottori Coastal Lowland II - 37
(3) Western Honshu Rugged Highlands II - 38
(4) Western Honshu Broken Lands II - 38
(5) Himeji-Yashiro Lowland II - 38
25. REGIONAL SUMMARY II - 39
26. NATURAL CRITICAL AREAS II - 41
27. ROUTES TO NATURAL CRITICAL AREAS
A. General
B. Description of individual routes
28. PRINCIPAL SOURCES
II - 41
11-4
11 -42
II -42
Published by
THE JOINT INTELLIGENCE STUDY PUBLISHING BOARD
Military Intelligence Division, G-2 Division of Naval Intelligence
Office of Assistant Chief of Air Staff, Intelligence Office of Strategic Services
AT WASHINGTON, D. C.
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Release 20
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