Examining the impact force of debris flow in a check dam from small-flume experiments

Abstract

Debris flow is one of the most hazardous disasters in mountain regions of Korea. Rainfall-induced debris flows have occurred more frequently during past decades due to climate changes. Especially, its threat on many lives and properties in urban or suburban areas have increased. To control debris-flow disaster, check dams have been constructed in forest watersheds since 1985. Although check dams that recently constructed in Korea are expected to function as debris-flow barriers, impact force has not been considered during design procedure. For effective structure design regarding debris-flow disaster, estimation of debris-flow impact force is necessary. Meanwhile, it is well known that impact force is closely related to the flow characteristics of debris flow. In this study, small flume experiments were conducted to analyze the influence of flow characteristics to impact force of debris flow. Flume slope, total volume, and viscosity of mixture were selected as experiment variables. As a result, faster flow velocity was observed on steeper channel slope and larger mixture volume condition. In terms of viscosity, sediment-water mixture flowed faster as the viscosity becomes lower. The effect of flume slope on flow velocity was different as the viscosity of mixtures. However, flowing depth was correlated only to total mixture volume. Impact force was positively correlated to flow velocity and flow depth. By comparing various impact force estimation model, the hydrodynamic model has been selected for the best method to appropriately calculate the design impact force for check dams in small forested watersheds.