Rainfall-triggered mass movements on steep loess slopes and their entrainment and distribution

Abstract

Mass movements are predominant geomorphic processes on steep hillslopes. However, the mechanisms governing the erosion and entrainment of mass movements remain poorly understood. In this study, experiments on natural loess slopes were conducted to induce a series of mass movements under simulated rainfalls in the Liudaogou Catchment on the Loess Plateau of China. A novel topography meter was used to observe random mass movements. A total of 499 mass movements in 42 rainfall events and an average of 11 mass movements for each rainfall event were observed. Three mass movement types were detected: landslides (67%) > mudflows (21%) > avalanches (12%). The volume of landslides dramatically increased through the entrainment of a wet gully bed material, and the volume of landslide mass was magnified by 29% on average through material entrainment. Based on the observed data, the probability of mass movement occurrences decreased with the increasing mass movement volume in a power-law relationship. The critical rainfall amount for mass movement failure was approximately 25.6 mm at a rainfall intensity of 50 mm h−1. These results can serve as guides to mitigate geological hazards and assess erosion processes on steep loess slopes of the Loess Plateau.