Study on the deterioration of ecological environment in mountainous disaster areas and on the essential conditions for environmental conservation in their reconstruction processes.

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1. This project aims at an investigation of deteriorationg ecological environment in mountainous disaster areas and of the essential conditions for environmental conservation measures in their reconstruction processes.2. Survey areas are located in ; a) Ohno-basin, Fukui-Prof., where problems of ground water depletion have very often been broken out recently, and b) Ohshika-Mura, Ina-valley, Nagano-Pref., where active reconstruction works have been going on after the severs flood disasters of 1961.3. In the survey areas, the geo-ecological maps of different stages were produced by means of aerial photographs, official survey materials and field works, and the process of changing environmental and social structures of the respective areas were investigated by the documents and filed observations.4. Main results of this research are as follows ;(1) In Ohno-basin, ground water used to be depleted through excessive pumping up of snow-melting water after heavy snowfall. But, level of ground … More water was usually recovered in summer season, thanks to the infiltration of irrigation water from paddy fields in the basin. Recently, however, ground water shortage occurs even in summer. It coluld be indicated that continuous depletion of ground water in the latest years has benn caused, at least partly, by the decreased infiltration of irrigation water from paddy fields in the catchment areas, where concreted channels and solidified field beds were constructed through the land-melioration works. In order to recover an optimum level of ground water supply in this area, some conservation measures for water supply, such as, restoring natural streams, land use planning after the geoecological considerations, and so on, which are successfully enforced in western Germany.(2) In Ohshika-Mura, many settlements, located in valley bottom and on talus or river terrace, were seriously damaged by land slide and muddy flood folw caused by the torrential rain of June 1961. Flood damages in this area were worsend by the devastation of mountain slopes and river channels during the war time. It can be highly appreciated, that the reconstruction works of the river channels along the damaged valleys were carried out mainly with natural materials instead of steel and concrete. The engineering methods of this type can be appraised as geoecologically effective for the river basin conservation, in view of the fact that the native kinds of vegetation, such as black alder, white birch, etc., have been gradually recovered along the stream channels during the thirty years after the flood damage of 1961. Less