Functions of check dam against debris flow: Comparison of two watersheds of Jiangjia Gully, Yunnan, China

Debris flow activity has recently caused serious property damage as well as loss of life in Yunnan, Southwest China. Moreover, ground failure caused by debris flow needs a long time to be recovered. The hazards of debris flow can be prevented or released by some engineering countermeasures such as erosion control. The check dam is one of the most effective structures to control the debris flow in the original area. Based on the examination of architectonic geology, engineering geology, rock mechanics and remote sensing geology, two major tributary gullies (one with check dams but the other without) of Jiangjia Gully in Yunnan Province, are compared in three aspects (channel longitudinal gradient, stability of lateral slopes and trailing edge of channel, soil erosion by debris flow) to prove that check dam or check dam series can: (1) effectively uplift the basic level of erosion of debris-flow channel; (2) reduce the longitudinal gradient of the debris-flow channel, and accordingly velocity slowed down and energy dissipated; (3) fix the channel and stabilize the slope so as to facilitate or restore the growth of the vegetation. In addition, several problems, needed to be taken into account during the design of check dam, are also discussed.