Watershed-oriented and multifactor-integrated identification and hazard evaluation of debris-flow-prone watersheds in Danba, China

Early identification of debris-flow-prone watersheds and determination of the initiation location of debris flows are prerequisites for debris flow monitoring and early warning. The high altitude, steep slope, dense vegetation, and influence of numerous factors triggering debris flows (FTDFs) in Danba, China, pose great difficulties in identifying debris-flow-prone watersheds and locating the possible initiation position of debris flows in this area. We propose a watershed-oriented and multifactor-integrated (WOMI) method for identifying debris-flow-prone watersheds in Danba. This method integrates various FTDFs, uses the watershed as an analysis unit, and detects the debris-flow-prone watersheds with a random forest (RF) algorithm. Moreover, we propose a statistical similarity metric to evaluate the rationality of identification results and introduce the extenics theory to evaluate the debris-flow hazard of the identified debris-flow-prone watersheds and their tributaries, thereby locating the possible initiation positions of debris flow in the identified debris-flow-prone watersheds. Based on 26 FTDFs derived from multi-source data between 2015 and 2019 in Danba, 36 new debris-flow-prone watersheds between 2015 and 2019 were discovered in this study. Nine debris-flow-prone watersheds and their 17 tributaries have very high hazard. "6.17" Meilong Valley debris flow just erupted in one of the identified debris-flow-prone watersheds in 2020. The statistical analysis and occurrence status of debris flows validated the proposed methodology and the identified debris-flow-prone watersheds in Danba. The research results of this article assisted in the investigation, early warning, and prevention of debris flows in Danba.