A coupled hydrologic-geomorphologic model of hillslope stability for shallow landsliding

Shallow landsliding in steep, soil-mantled landscapes can generate debris flows which scour low-order channels, deposite large quantity of sediment in higher order channels and pose a significant hazard. The hazard results in high risk where development has encroached on debris flow source and run-out areas. These shallow failures are triggered during rainstorms or periods of rapid snowmelt when shear strength is reduced because of an increase in pore-water pressure. This increase may be directly related to rainfall infiltration and percolation (saturation from above) or may be the result of a build-up of a perched water table or a groundwater table (saturation from below). In these conditions, a slope failure can occur within the soil mantle or at the contact with the impermeable boundary below. The detached mass then slides downslope, commonly increasing in water content and forming a debris flow further downslope.