Predicting debris-flow scour depth downstream from a check dam

Abstract

Debris flows often pose great threats to people’s lives and property in mountainous regions. For example on August 8, 2010, a debris flow with a volume of 220×104 m3 occurred in ZhouQu county, Gansu province, China. The debris flow resulted in not only significant loss of farmlands, but also in 1,248 deaths and 496 people missing. The construction of check dams in debris- flow valleys is a useful way to mitigate deaths and damages. Herein, we investigate scour downstream from check dam spillway structures. We propose that the main parameters which determine scour depth of a scour hole downstream from check dams, include flow density, flow depth, flow discharge per unit width, and acceleration due to gravity. Physical experiments were also carried out to investigate debris flow movement and scour characteristics. In addition, a theoretical expression was deduced to predict the maximum scour depth downstream from check dams. There was a good correlation between experimental data and results predicted from theory. The results obtained in this paper can provide constraints for the design of check dams in mountainous areas.