Hydrogeomorohic studies on watershed-environment management in the monsoon zone in changing global environment

通过对日本东北部仙台附近丘陵谷头微地貌、土壤地层、土壤水分和径流的连续观察和分析，揭示了具有高蓄水量的厚土层的上水头空洞和由有限体积的渗透土壤/风化基岩组成的下水头空洞的组合，控制了通流，促进了管道径流的产生。对日本中部火山坡地的径流和土壤的观测和分析证明，径流是由安迪索尔A层快速垂直渗流和B层贯通流共同维持的相当迅速的径流，以及来自下伏火山碎屑流沉积的更稳定和大量的径流共同贡献的。在日本东北部一座风力极大的低山峰上，对地表石块迁移和当地空气和土壤气候的反复观察表明，霜冻蠕变及其相关过程在冬季导致石块错位达1米。研究了日本中部一处硅质岩流域深部滑坡的发生与地质构造和基流径流的关系。对湿润、温带和热带环境下花岗岩流域的河谷形态和沉积物的对比观察表明，崩解和分解的差异提供了河谷特有的垂直和横向形态。还分析了日本几个上游流域的坡面过程对植被的不同影响。上述结果综合考虑了即将到来的气候变化对温带季风区流域环境的影响。

It was revealed by a continuing observation and analysis of micro-landforms, soil stratigraphy, soil moisture, and runoff in a valley head in the hills near Sendai, northeastern Japan, that a combination of upper head hollow which has thick solum of high storage capacity and lower head hollow composed of permeable solum/weathered bedrock of limited volume controls throughflow and promotes the generation of streamflow from pipes. Observation and analysis of runoff and soil at volcanic footslopes in central Japan proved that streamflow is contributed by both rather prompt runoff sustained with a combination of rapid vertical percolation in A horizon and throughflow in B horizon of Andisol and more steady and large quantity of runoff from underlying pyroclastic flow deposits. Repeated observation of surface stone migration and local air-and soil climates on a low mountain peak with extremely strong wind in northeastern Japan showed the occurrence of frost creep and associated processes resulted in stone dislocation up to 1m in a winter season. Occurrence of deep-seated landslides was investigated in relation to geologic structure and baseflow runoff in a chert watershed in central Japan. Comparative observation of valley forms and sediments in granite watersheds in humid temperate and tropical environments suggested that the difference in disintegration and decomposition provide the characteristic vertical and cross-profile forms of river valleys. Differential effects of hillslope processes on vegetation were also analyzed in several upstream watersheds in Japan. The results as above were integrated into a consideration of effects of coming climate change to watershed environments in the temperate monsoon zone.