山地流域における出水と土砂流出(16)

Abstract

The sediment runoff problem in a basin is one of the most significant studies in thefield of the river environment, water resources and disaster prevention. The sedimentprocess includes sediment production, sediment transport and sedimentation down stream.These processes simultaneously or alternately occur in the several areas in the basintaking various manners responding the characteristics of the basin and the magnitudes of thegiven causes. Thus, the total sediment runoff system comprises many complex subsystemsand could be analysed as a process-response system to relate input of precipitation withoutput of sediment.The sediment production system which is one of the subsystems in the sediment runoffsystem could be analysed as a morphological system relating angle of slope to variableincluding depth of superficial material, distribution of grain size, soil texture and the externalcauses.We have conducted the observational studies for sediment runoff process in an experi-mental basin where the rate of sediment runoff is the greatest in Japan and various modesof sediment yield and runoff can be observed depending on the difference of the topographical, geological and climatic conditions in the subbasins. In this paper, measuring techniques forsediment yield are described, and the rate of sediment yield is discussed in relation to theslope angle, rainfall intensity, freezing and thawing effect, and the properties of materialsuch as grain-size distribution and conpressive strength