Abstract
Grid type sabo dam is commonly constructed in order to control the debris flow. The opening of grid dam is choked with big rocks included in the front part of the debris flow, and the dam can trap the following muddy flow as a closed type dam after the blockage of opening. In this paper, we proposed a new simulation method that can reproduce the one-dimensional riverbed variation in a mountainous river with a grid dam. In the model, we regard the grid dam as a closed type dam whose height varies in time through the blockage. The one-dimensional governing equations for a stony debris flow are employed and the sediment material is composed of two grain-size classes. Only the bigger sediment causes the stoppage of the grid dam opening, and increase the height of the dam. The temporal change of the dam height is estimated by using the probability of the blockage that is influenced by the sediment concentration, flow depth, sediment diameter and distance of columns of grid dam. We try to clarify the grid dam's function for the debris flow control by the simulation model. From the calculation, it is shown that the grid dam can reduce the peak sediment discharge of a debris flow more effectively than the closed type sabo dam.
