Experimental Study of Sabo Dam Physical Measures Against Subsequent Sediment Flow Following Debris Flow Deposition

Typical countermeasures against subsequent sediment flow following debris deposition include channel works and sand pockets ; however, these measures require extensive open areas. Therefore, alternative countermeasure designs must be considered for residential areas with high population density. The objective of this study was to propose a novel method for capturing subsequent sediment flow following debris deposition at a sabo dam. We installed three types of debris capture devices (subsequent sediment flow breaker, water-absorbing polymer, and sub-dam) to investigate their effects singly and in combination. Subsequent sediment flow characteristics were evaluated in flume experiments using models of the three capture devices. Simulated debris flow was trapped by the sabo dam model, and subsequent sediment flow was controlled by the three countermeasures installed downstream of the dam. Sediment was separated from water using the subsequent sediment flow breaker and then trapped by the sub-dam, and water was absorbed by the polymer. We measured 1) the volume of sediment collected by the breaker, 2) time elapsed from the sabo dam to the end of the flume, 3) peak discharge, and 4) concentration of the subsequent sediment flow. Sediment volume decreased and elapsed time increased as the sediment flowed through the experimental countermeasure structures, leading to dramatic reductions in peak discharge and sediment concentration downstream of the sabo dam.