小流域からの豪雨時土砂流出の予測

Abstract

A method was given that predicts the number of shallow landslides which occurin a mountainous basin with complex topography in case of a severe rain storm ofarbitrary intensity and time sequences. The method is based on the analysis ofinfiltrated flow, surface flow and the stability against slide in the top soil layers.The method was proved feasible by comparing to the actual data. Each slide unitwas allotted to a certain time and space, and if the route from the slide to thevalley bottom was steeper than 20 the slid earth block was supplied to the streamat the end of the route and eroded by the stream flow simultaneously calculated.The system of equations to analyse the sediment transport and channel bedvariation was used to estimate the sediment yield from the basin due to suchprocesses. The quantity of sediment yield changes with the distribution pattern ofthe landslides in the basin, but the width of variation was proved small incomparison to that change should be due to variation of other factors.