Debris-flow mitigation measures and an application case in a small-scale watershed in China

Abstract

The Wenchuan earthquake in China (May 12, 2008) triggered numerous debris flows, some of which caused serious secondary disasters, such as in Wenjia gully (Sichuan Province) and Sanyanyu gully (Gansu Province). To solve this problem, a planning method for debris-flow mitigation engineering measures was proposed based on watershed and river sediment transport characteristics. This method aids in the selection of engineering measures to effectively prevent secondary disasters and control unconsolidated soil and debris-flow movement from upstream to downstream. Several measures are considered in the proposed method, including check dams and transverse structures built across gullies, which are important engineering measures in debrisflow hazard mitigation. Based on the developed planning method, new types of check dams were proposed, the regulation effect of sediment particle size in slit check dams was qualitatively analyzed, and the design parameters (e.g., deposition slope, deposition length, and dam height) of the check dams were deduced. Moreover, a series of drainage channels was proposed to cross highways and discharge debris flows into the river or debris-flow deposition basin below. Finally, an engineering application case in Xiaogangjian gully, Sichuan Province, China, was examined using the proposed watershed planning method, in which a series of check dams with different orifices sizes was constructed. The engineering application results provide useful data for developing check dams as a restoration tool and hazard mitigation technology in small watersheds.