Exploration of design parameters for a dewatering structure for debris flow mitigation

A small-scale flume experiment was conducted to assess the design considerations for a horizontal dewatering debris-flow-brake. Design parameters and a design sequence are suggested, which were previously unavailable in the published literature, and are developed from comparison to other mitigation design strategies and results of laboratory flume experiments. It is concluded that the most important input parameters into the design of a debris-flow dewatering brake are the expected thickness of the debris-flow deposit and the channel shape. The volume of debris that can be stopped and stored by this mitigation design is a function of these parameters as well as channel slope. The thickness of the debris that is arrested on the grate depends on the depositional properties of the debris-flow mass, such as the unit weight of the material, but in small-scale experimentation thickness was not affected by volume of the debris available. The ideal brake is a free draining surface with an aperture smaller than the D90 value for the debris-flow grain-size distribution.