本論は, 川崎市を事例としてとりあげ, 都市水害の常襲地域の形成過程を明らかにしようとしたものである。まず常襲地域を選択し, 水害の特徴について調べ, 典型的な都市水害の常襲地域であることを明らかにした。そして, 土地条件の悪い地域の都市化が, (1) 戦中期の軍需工場進出期と, (2) 戦後の高度経済成長期 (とくに1950年代中頃～60年代初め) に, 集中的に進行したことが判明した。このうちとくに (2) の時期について, アンケート調査の結果によって居住地選択の特徴が明らかにされた。これらの地域には, 戦後をとおして“若夫婦のみ”ないし“第1子が小学生”程度の特定のライフ・ステージの家族が居住地として選択してきており, 選択の際には通勤・通学や地価・家賃といった条件が主として考慮されて, 水害のことはほとんど無視されていたのである。このような居住地選択がなされることを前提として宅地化がなされ, 結果として, 都市水害の常襲地域が形成されるに至ったと考えられる。

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A flood-disaster is not a mere natural phenomenon but a regional one which figures as synthesis of natural conditions and social conditions the latter of which have influence upon the former. Starting from this point of view, I chose as the object of investigation the flood-disaster on August 15th, 1953, in the southern part of Kyoto Prefecture (Minamiyamashiro).
The distinctive feature of the damage by the flood in Minamiyamashiro was destruction of houses and casualities done to men. Although it was partly due to the torrential rain limited to one particular locality, the immediate cause was that the dykes of the up-floored rivers, many of which are seen in this district, were broken. The flood-disaster at Ide-cho serves as an example of the damage done by the above-mentioned cause. And, the up-floored rivers in the district were made by human agency, not by nature at all. Namely, grit and sand were carried down the lower reaches of a river owing to reckless deforestation at the basin of the uppor stream; and people at the basin of the downstream made an embankment higher and higher lest the grit and sand should not flow into the ploughed land. Why, then, such land utilization as this is still conducted which is easy to cause a flood-disaster? The answer to this was worked out by analysis as to how infinitesimal peasantry who owed woodlands in the district ran their works. By the analysis were known the actual circumstances of the infinitesiman farmers who are unable to maintain themselves by any other means but reckless deforestation and cultivation of tea garden; and that woodlands denudation is made worse by the fact that there are ample funds for facilities of forest roads which promote deforestation, while there is deficiency in circulating capital for expenses of afforestation which such farmers as aforementioned can not afford. In short, what brings a flood-disaster is a contradiction between the public good (conserving water power) and the economic phase (profit made by deforestation) of woodlands.

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The one-six hundredth cadastral maps of Japanese villages were prepared in or a little before 1873, but they are too incorrect to measure the area on them. Therefore it is now urgently necessary for our own country to make a modern correct maps of large scale and to survey land capability rind utilization in every acre by it. Such a map and the results of survey should be the most fundamental material to the improvement of landuse, and to synthetic land plannings.
In the Land Division of the Japanese Resources Committee established in 1947 a Subcommittee was organized to research how the aerophotographs of one to 40, 000 are valuable for the understanding of real landuse, and to determine the method for the detailed land utilization survey in every piece of cultivated land to which the large scale map made from the developed aerophotograph should be adopted. This base map of one to 2, 500 in scale is to be made from the one thousandth aerophotograph by the development and amendment of distortion in aerophoto.
The staffs of the Geographical Institute of Tokyo University and Tokyo Bunrika University were entrusted with the task to determine the method for the fine land utilization survey and to investigate land use in field under the method on that base map. They arranged to adopt the long fractional code method for the survey and its descriptions which Prof. V. Finch and D. Hudson practised and developed.
Our survey items consist mainly of the observable phenomena in field; but they partly include the questionings to the farmer. The items are as follows: I natural elements- 1. the topographical location of each cultivated land. 2. the direction and degree of slope. 3. the duaration of sunshine. 4. the humidity of soils. 5. the color of soils. 6. soil texture. 7. the amount of gravel contained. 8. the depth of top soil. 9, the acidity of soil. 10. soil type. 11. the efficiency of irrigationa and drainage. 12. disasters (soil erosion, soil accumulation, and etc.) II human elements- 1. main sort of landuse 2. the sort of crop (intercrop, crop rotation, endicsing crop, etc.) 3. the ..width and direction of ridge, and the height of terrace. 4, tillage method. 5. weeding rnethod. 6. length of fallows. 7. the distance to the farmer's house. 8. the quantity and kind of manure given a year, 9. farmer's own land or not. 10. the age of land cleared or of land improved. 11. labor days a year. 12. the present degree of arable land.
These items were checked to select the necessary elements in every piece of cultivated land in a section of Tsurukawa-mura of Tokyo Prefecture, included in Tama Hills, The fractional code was described in note-book. The results of the land utilization survey in Tsurukawa-mura may be described in another paper.
The survey like this may be allowed only in sampling, for it consumes too much expenses, labor, and time. Then it is necessary to survey landuse in the smallest homogeneous unit area. For the demarcation of this unit area the thoughts of “Ökotop or natlürliche Standortseinheit” are very sugestive. The survey items on this unit area were also devised by us but were not yet checked in field.

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