ABSTRACT
The debris flow event in Hofu City, Yamaguchi Prefecture, Japan on July 21,2009 yielded a large amount of sediment transport and woody debris in the mountain river basin, where a closed type of check dam and an open type of check dam were built (Maricar et al., 2011). Based on laboratory tests, the debris flow control by these check dam was studied. This paper compares the deposition process of sediment grains and pieces of wood at the open and closed check dam in a laboratory flume experiment. The experimental results showed that the open check dam trapped the wood pieces and the trapped pieces deposited the sediment grains behind themselves. On the other hand, the closed check dam made most of wood pieces pass through the check dam and most of sediment grains get trapped in the water pool behind the closed check dam.
