土石流対策に関する事例研究

抄録

Introduced herein is a type of debris flow that hit a torrent equipped with one closed type and one open type sabo dam. Those two sabo dams could not check the debris flow as was expected. As a result, certain types of sediment flowed over them and damaged a number of houses standing in the downstream alluvial fan. We gained some knowledge from the analysis of the event. The closed sabo dam must be kept empty through excavation to be capable of holding the utmost sediment deposit. The opening of a grid type open dam must be made narrow at its upper part because the grain size of the sediment of the subsequent flow is so small that the sediment cannot be trapped if the upper section of the opening is wide. When designing the debris flow control structures, it is necessary to consider that debris flow starts not only at the uppermost stream, but also at various slopes.