An interpretable framework for the hazard assessment of debris flow based on an improved AHP-EWM method and the SHAP model: a case study of Heishuiwan gully

Debris flows are significant geological hazard in Beijing mountainous areas. As a non-engineering means, hazard assessment is instructive for debris flow prevention and control. A rational assessment framework should not only sufficiently describe various attributes of the debris flow system but also provide objective and reasonable hazard zoning results, along with interpretive analysis of the assessment outcomes. In this study, the debris flow located at Heishuiwan Gully in Beijing was taken as a case study for debris flow hazard assessment. The combination of an improved AHP-EWM method and the SHAP model was successfully applied to develop an interpretable framework for hazard assessment of a single-gully debris flow, including the relative weight calculation and interaction effect analysis of the assessment indicators. The reliability of the improved AHP-EWM method was quantitatively validated by comparing with the numerical simulation results of FLO-2D. The rationality of indicator selection was explained through the SHAP model. The hazard zoning result obtained from the AHP-EWM method was consistent with that of FLO-2D, with a nearly linear relationship between the area of high-risk zones and rainfall intensity. The analysis using the SHAP model revealed that elevation had the most significant impact on debris flow hazard due to its synergistic effect with other evaluation factors. This interpretable hazard assessment framework can provide targeted guidance and recommendations for the prevention and control of single-gully debris flows.