Estimating the charsteristics of woody debris mechanism in terauchi dam reservoir catchment

In 2017, numerous amounts of woody debris was exported into Terauchi dam reservoir as woody debris because of a heavy rain which seriously damaged Northern Kyushu. It took a lot of time and it was costly to remove all the woods. Although inevitable damages caused by woody debris have been increasing recently, detailed mechanism of woody debris throughout a catchment is still unknown. Thus, this study was conducted in order to understand the mechanism of woody debris and consider its characteristics in a catchment scale by taking an example of Terauchi dam reservoir catchment. The woody debris transport model was applied in this study, which expressed 2 types of woody debris export. One is the flood flow typed export, which happens along with a large amount of woody debris production. The other is the base flow typed export, which happens in a normal condition without woody debris production. The result indicated that a large amount of woody debirs production in 2012 partially affected to the vast amount of woody debris export in 2017. In addition, a previous study which analyzed dam reservoir catchments in Iwate prefecture showed that Terauchi dam reservoir catchment had a tendency to cause flood flow typed export easily. Moreover, it turned out that accumulated woody debris in Terauchi dam reservoir catchment were likely to be exported easily as the base flow.