Evaluation of debris-flow risk in Xiaohongyan Gully of Baihetan hydropower station on the Jinsha River

Abstract

Debris flows are common geological disasters that strike the southern mountainous areas in China frequently, posing harm to the construction and safe operation of cascade hydropower stations. In this study, we conduct a geological survey to analyze the topographic conditions for debris-flow triggering at the Xiaohongyan Gully of Baihetan Hydropower Station, Jinsha River. Then, we continue with a laboratory test and analyze the bulk density, speed, volume, and impact force of debris flows as well as the total volume of a debris flow and the total solid material content. Finally, we predict how a debris flow develops and how it affects engineering construction, thereby proposing suggestions on how to effectively control and prevent debris flows. The results revealed that debris flows in Xiaohongyan gully met the topographic, material source, and rainfall conditions. The total volume of loose solid material sources in this gully was 218.14×104 m3, among which the volume of unstable material sources that might participate in debris flow activities was 26.46×104 m3, indicating a gully rainfall-induced low-frequency large-scale diluted debris flow. The main parameters of Xiaohongyan debris flow gully with a 50-year return period were as follows: bulk density (1.52 t/m3), speed (3.71 m/s), and peak volume (173.63 m3/s) of debris flow, the total volume of a debris flow (55,000 m3), solid material content (17,200 m3) and overall impact force (2.83 kPa) of the fluid. The study results provide a beneficial reference for evaluating, preventing, and controlling debris flow disasters in major engineering construction areas.