ESTIMATION OF DEBRIS FLOW CONTROL WITH SABO FACILITIES BASED ON NUMERICAL SIMULATION

Abstract

Prediction of debris flow characteristics and estimation of debris flow control with sabo facilities such as check dams and channel works in a mountain torrent are discussed, based on the results of field survey and numerical analysis. In the Ohzedani River, a tributary of the Sendai River, a very active sediment runoff took place in September 1961 due to the second Muroto typhoon. A one-dimensional numerical simulation is conducted in order to investigate the variation of debris flow characteristics along the river reach with sabo facilities. The analytical results show that debris flow discharge increaseseveral orders of magnitude compared to water, and that the sediment transport rate varies with bed slope and river width. Check dams are effective for the reduction of sediment transport when the initial bed slope of deposition area at the upstream of the dam is not steeper than that of equilibrium slope of debris flow. Flow path is fixed with channel works and it makes a great contribution for the protection against debris flow flooding. The computational condition of erosion depth on the bed has much effects on these numerical results.