土地改変研究への環境地形学的アプローチ

Abstract

In the land transformation studies geomorphology mainly deals with two aspects: i.e., direct transformation and induced geomorphic processes. This paper is concerned with the latter from the perspectives of climatic geomorphology. Climatic geomorphology that attaches importance to the following aspects constitutes the essential part of environmental geomorphology applicable to land transformation studies and environmental management:1) spatial variability in land conditions, 2) spatial variability in geomorphic processes characteristic of regional and local climatic conditions, 3) variability in space and time in climatic variables operating as geomorphic agents, and4) nature and resources of the land produced through the past climatic/environmental oscillations.Based on this framework, general tendencies and implications of accelerated erosion and man-induced land deterioration in Japan are summarized so as to formulate the spatial variability in the form and intensity of induced geomorphic processes under different climatic conditions. It becomes clear that the transformation of the land surface form and cover almost always results in the enhancement of geomorphic processes characteristic of regional and local climatic conditions. Combined effects of land transformation and climatic anomalies often cause geomorphic hazards due to rapid gullying, mass movements, etc. Examples of intensification of human impact on the land caused by recent climatic anomalies are reviewed briefly.The author hopes that the concepts of environmental geomorphology introduced here may shed a new light on the fields of civil engineering responsible for a better modification and the management of terrestrial environment. In Japan, the conception that most of land properties including soils are the product of the past climatic/environmental changes and hence a non-renewable resource has hitherto been very weak. The soildification of this conception requires a positive discussion among the related fields of Quaternary research.