INFLUENCE OF SLOPE FAILURE PROCESS ON FLOOD AND SEDIMENT RUNOFF IN A MOUNTAIN RIVER

Abstract

A heavy rainfall often causes slope failures and landslides. The earth mass produced by a large scale slope failure buries a valley, and sometimes forms a landslide dam. Water and sediment runoff process in the river channel are strongly affected by the formation and deformation of landslide dams. In a report of the natural disaster 2004, the earth mass sometimes breaks into several blocks, and each block starts to move separately. Such slope failure process seems to influence on the landslide dam formation. I apply 2-D hybrid debris flow model to the landslide dam formation process, and investigate the influence through the calculations in different occurrence timing of slope failure. The model was proposed to explain the runoff process of the soil block including the fluidization phenomenon, which is composed of the usual two-dimensional debris flow model and a tracking model for soil block movement as solid. The deformation process of landslide dam and the water and sediment runoff process are calculated by a usual two-dimensional bed variation model.