The Trapping Effects of Different Vertical Columns Spacings of Adjustable Check Dam against Debris Flow and Driftwoods

The occurrence of short duration and intense rainfall events has been more frequent as a result of extreme climate and aggravated sediment-related disasters such as debris flow and landslides. Check dams, as common measures to trap gravels and driftwoods, are used to reduce the harm to downstream residents during disasters. Adjustable check dams are more flexible than general check dams because of the bars and the columns of the dam can be removed and reinstalled so it provide flexibility to adjust the passing sediment amount and balance the sediment transport in the watersheds. However, the driftwoods in the river, trapped by the adjustable check dam, become a variable to the ability of the check dam to adjust the passing sediment. In this research, we use a laboratory channel with a width of 20 cm and a length of 2 m to simulate the blockage of driftwoods under different vertical columns spacings of the adjustable check dam. Appropriate vertical columns spacing of adjustable check dam are found via analyzing the amount of driftwood passing through the check dam. Moreover, sediment is added in the experiment to simulate debris flow to find the relation between the vertical columns spacing and the representative particle size. The results can be a reference for the design of the check dam and an instruction for operating adjustable check dam.