Assessing the informativeness of a coupled surface–subsurface watershed model for understanding debris flow: a hydrological perspective

Characterization of debris flow is critical to both risk assessment and hazard mitigation. Recent technologies enable on-site environmental monitoring sensors for geological disaster monitoring. However, the spatio-temporal understanding of debris flow in remote mountainous areas is still limited due to difficulties in observation networks and its complex driving conditions. Here we apply a coupled surface-subsurface hydrologic model to examine the characteristics of the water movements near the debris flow sites in Southwest China. Our approach captured the temporal dynamics of infiltration, redistribution of soil moisture, groundwater storage, and lateral groundwater fluxes. The lateral groundwater flux and groundwater storage were informative indicators in identifying debris flow location. Such informativeness was only effective when hourly dynamics were analyzed. Our findings provide new insight into quantifying the debris flow susceptibility. This study suggests that the coupled surface-subsurface watershed modeling approach can be informative for preliminary monitoring, planning and management problems of debris flow.