不透過型砂防ダムの持つ流木捕捉能力

抄録

In the present design criteria, woody debris trapping capacity by impermeable type Sabo dam is estimated to be less than 1% of sediment control volume in debris flow zone. However, it has been reported that the impermeable type Sabo dam, already filled with sediment, traps woody debris more than the criteria. Hence, it has become necessary to review this issue.
Authors analyzed the data of the trapped woody debris by impermeable type Sabo dams. Furthermore, we conducted flume experiments by using various lengths of wood models. Consequently, it was confirmed that impermeable type Sabo dams showed high woody debris trapping rates in some cases. Following results have been obtained by this study.
1) Woody debris trapped by impermeable type Sabo dams are classified in three patterns, a) trapped by spillway clogging, b) trapped by the mixing of the debris flow in the sediment and c) trapped by friction in the sediment trapping zone.
2) The impermeable type Sabo dam, already filled with sediment, traps 13% of sediment control volume of the woody debris.
3) The maximum lengths of the wood in the trapped woody debris by clogging the spillways are more than 1.3 times of the width of the spillways.
4) The two strong factors concerning the woody debris trapping rate are the relation between the maximum wood length and the width of the spillway, and the sediment filling condition of the impermeable type Sabo dam.
5) Woody debris trapping rate increases by mixing long wood models in the woody debris.
6) Woody debris trapping rate increases in proportion to the mixture rate of long wood models in the woody debris. However, there are some exceptions to this relation and this subject is necessary to be investigated in future studies.