Coupled dual permeability with runoff model for simultaneous analysis of rainfall-induced seepage and runoff

Rainfall-induced slope instability poses a significant geotechnical challenge, particularly during heavy rainfall events. Traditional seepage models often neglect the combined effects of surface runoff and preferential flow, leading to limited predictive capabilities. This study presents a novel coupled dual permeability with runoff model (DPWRM) to analyze runoff and seepage during rainfall-induced preferential flow on unsaturated slopes. Combining the kinematic wave equation and dual permeability model, this approach addresses the limitations in existing methods for slope seepage predictions under intense rainfall. First, the critical role of preferential flow pathways enhanced infiltration and drainage efficiency, influencing seepage in single permeability model. Second, the DPWRM integrates infiltration dynamics, pore water pressure and runoff velocity to simulate hydrological responses. A physical model test validated the numerical model, demonstrating accurate predictions of cumulative runoff, pore water pressure variations. The results revealed significant impacts of runoff and soil heterogeneity on hydraulic conductivity and water distribution. This research provides insights into slope hydrology and geotechnical applications, offering practical strategies for managing rainfall-induced slope failures.