Debris flow hazard characteristic and mitigation in Yusitong Gully, Hengduan Mountainous Region

Abstract

Catastrophic debris flows have the potential to devastate structures, infrastructure, and inflict severe economic losses and casualties. Situated within the Xianshuihe fault zone, Yusitong Gully has a watershed area of 25.88 km2, with a main channel length of 9.18 km and a gully bed gradient of 310‰. The combination of rainstorms and subsequent runoff makes the formation of debris flow all too common, posing a threat to both Yusitong Village and the Kangding-Mugetso highway on the alluvial fan. This study encompasses a comprehensive investigation of field conditions, calculations of essential parameters, and dynamic process simulations to better understand debris flows in Yusitong Gully. By estimating the magnitudes of debris flow within return periods of once-in-a-century, once-in-fifty-years, and once-in-twenty-years, including the peak discharge and total volume of a single debris flow event, we can accurately assess the potential risks. Additionally, a numerical technique is employed to simulate debris flow occurrences at different frequencies within Yusitong Gully, considering scenarios both with and without implemented control measures. The results demonstrate that the highest hazard level is located at the top of the alluvial fan, but significantly decreases after the execution of control measures. This study serves as a reliable scientific foundation for analyzing hazards and formulating effective mitigation plans, not only for Yusitong Gully but also for other mountainous catchments.