A NATIONAL SUMMARY RECENT TRENDS OF LARGE-SCALE LANDFORM-TRANSFORMATION IN JAPAN

Abstract

Large-scale landform transformations for various purposes of land developments have been recently active in Japan. They have required the researchs from the viewpoint of anthro-ogenic geomorphology which contains both man-made and man-induced landforms and p related phenomena in its scope. This paper reveals the recent trends of the change in types of landform utilized and estimates the magnitude of man-made landforming processes in the intensely developed lands in Japan. Because the statistics showing the actual states of landform transformation have not been sufficiently prepared yet, the estimation of magunitude of artificial landforming processes in this study progresses inevitably in a felicitous combination of selected detailed surveys and effective generalization. First, landform modification types and magnitude are investi-gated with the aid of very large-scale scheme drawings etc. at the small number of typical development sites for each purpose and in each type of landform. The area of develop-ment and the volume of artificially-removed earth provide the simple indices of landform-modification magnitude. The greater volume between artificially cut material and filling one is used to represent the volume of artificiallyremoved earth in the site because most of earth cut from higher location is usually applied for filling in the lower location within the same development site except for ones in the flat lowlands and the reclaimed lands. The normal depth of surface disturbance is defined as the average of the ratio of the above volume to area of the site for both every development purpose, e. g. residential, industrial, agricultural, etc., and every geomorphic location which is classified into the follwing four intermediate-scale geomorphic units: the lowlands (Holocene alluvial and coastal plains), the terraces (mostly of late-Pleistocene age), the hills (mostly composed of early-Pleistocene and/or Neogene de-posits with mid-Pleistocene cover in part) and the mountains. The areas for several pur-poses of development sites, which are usually provided with administrative districts, are also retotalized according to these geomorphic units. The normal depth of surface disturbace and the total area of development, both of which are arranged according to the development purposes and the intermediate-scale geomor phic units, are applied for the estimation of the total volume of artificially-removed earth. Some results of the estimation are as follows: 1. The land development for various purposes became very active around 1960 and has been advanced with distinct decrease in the mid-1970's. The trends correspond well with changes in the national-scale socio-economic activity. 2. The rapid increase of intense land-developments since 1960 has proceeded in concurrent with the remarkable changes in locational condition of landform for residential, agricultural, and industrial sites from the lowlands and terraces to the hills, and further to the mountains in the case of agricultural development. For instance, more than 40% (in area) of the newly-developed residential sites are located in the hills. Moreover very extensive area of golf courses, which may exceed the total area of residential development, has been developed during the same period and most of them are located in the hills. 3. The increase of development area and the changes in its locational condition of landform to the hills have caused distinct rise of artificially-removed earth volume. The total volume of earth removed artificially during 20 years since 1960 in Japan may reach the order of 1010m3, which means 1 or 2×103m3 of earth material has been removed an-nually from every1km2 area.