Rainfall induced shallow landslides on sandy soil and impacts on sediment discharge: A flume based investigation

Abstract

The impact of rainfall induced shallow landslides on hillslope sediment discharge is not well understood. The aim of the research was to investigate how varying soil profile depth affects the location and occurrence of shallow slope failures as well as how it impacts sediment yields. Four flume based experiments were conducted using a sandy soil and a 30 and 10 degree compound slope configuration under average rainfall intensity of 50 mm/hr for soil profile’s depths set to 20, 30, 40 and 50 cm. Sediment discharge and runoff were collected from the flume outlet at 15 minute intervals. Changes in soil profiles after landslides and changes in soil properties like soil armouring were also recorded. Results showed that sediment yields at the outlet, before landslides occurred, were very low and limited to the finer soil particles as would be expected for a sandy soil. However subsequent variations in sediment discharge were strongly related to failure events and their proximity from the outlet. The sediment yield was also affected by the original soil thickness. The results provide a clear link of landslides and sediment discharge to hydrological processes occurring in the hillslope which are related to the soil thickness.