Quantifying and modeling post-failure sediment yields from laboratory-scale soil erosion and shallow landslide experiments with silty loess

Abstract

Rainfall events on steep hillslopes can cause both soil erosion and shallow landslides. These processes interact with each other and need to be studied in an integrated way to understand hillslope sediment yields. The main aim of this research is to study post-failure sediment yield following landslides that alter local slope gradients. A laboratory flume under a rainfall simulator was used to quantify erosion and shallow landslides in fine-grained silty loess soils. The flume was divided into an upper and a lower section; the slopes of which could be altered. A total of 12 experiments were conducted on slopes ranging from 35° to 47° in the upper and 5° to 10° in the lower flume sections. Shallow landslides were triggered in four of the 12 experiments. Sediment and runoff were collected from the flume outlet every minute during landslides and every 10 min before and after landslides. Changes in the soil slope after landslides occurred were recorded. Results showed that peak sediment yields were related to landslide occurrence and proximity to the outlet. Post-failure reduction in sediment yields was related to the evolution of the hillslope after slope failures. A simple rule-based soil redistribution model of runout distance was validated using the experimental results. The Water Erosion Prediction Project (WEPP) model was used to simulate runoff and soil erosion during pre- and post-failure rainfall events. Predicted runoff rates and sediment yields using WEPP were in good agreement with those measured in both pre- and post-failure events, indicating that the model can be used successfully as part of an integrated approach to modeling sediment yields in landslide-prone landscapes.