Impacts of Landslide Disturbance on the Hydrological Responses and Slope Stability in the Loess Plateau

Rainfall-triggered shallow landslides reshape hillslope topography and alter the physical properties of the underlying surface as well as the characteristics of soil water movement.However,the impacts of changes in soil saturated hydraulic conductivity (K_sat) caused by the pre-sequence landslide disturbance on the subsequent slope instability susceptibility remain unclear.To elucidate how the spatial heterogeneity of K_sat caused by three landslide-disturbance modes (i.e.,slope top collapse (LS1),overall slip (LS2) and slope toe collapse (LS3)) affects the hydrological response process and slope stability,based on the sampling data and field investigation,physics-based numerical simulations were conducted in a typical hillslope of the Chinese Loess Plateau by coupling the distributed hydrological model (InHM) and the infinite slope model (ISA).The results show that:(1)The spatial heterogeneity of soil K_sat caused by landslide disturbance significantly changed the runoff generation and confluence processes on the hillslope.The runoff initiation time was averagely advanced by 25%~46%,and the peak value decreased by 20%~30%;(2)Landslide disturbance affects the soil water storage capacity and distribution characteristics inside the hillslope.The infiltration depth decreases by 0.20m on average in the stripping area,and deepens by 0.10m on average in the landslide deposit;(3)The changes of hydrological processes such as infiltration enhancement,shallow soil water perching and pore water pressure surge caused by landslide disturbance lead to the increase of slope weight,poor drainage and weakening of anti-sliding force,which induces secondary landslides;(4) The risk of slope instability is aggravated under the three landslide disturbance modes,especially in the stripping area.The depth and scale of potential secondary landslide vary with vegetation coverage conditions.These results help explaining the phenomenon of landslide-path-dependence from the perspective of K_sat heterogeneity,which can provide theoretical surpport for the prevention and control of landslide disasters in the Loess Plateau.