Lateral sediment connectivity of landslides occurred under a heavy rainstorm and its influence on sediment yield of slope-channel cascade on the Loess Plateau

Abstract

The rate at which sediment enters the channel network in the landscape reflects lateral sediment connectivity of the landscape and has significant implications on the hydrological processes in a catchment. The main objective of this research was to quantify the lateral sediment connectivity of landslides and explore their relationship to the sediment yield of slope-channel cascades. Combining fieldwork and unmanned aerial vehicle techniques, we mapped all landslide inventories and calculated the amount of soil erosion. We proposed a new lateral sediment connectivity index (LCI), which takes into account landslide area density, landslide connectivity characteristics, and landslide potential transport distance, to explore whether landslides that occurred under heavy rainstorms affect the sediment yield in slope-channel cascades through legacy effects. Results showed that the area of landslides ranged from 0.2 m2 to 1100.07 m2, and the soil erosion amount of landslides ranged from 0.21 t to 1690.81 t during the rainstorm that occurred on 4 August. 2020 with a cumulative rainfall of 216.4 mm. The LCI of landslides was more closely related to the sediment yield of slope-channel cascades after the rainstorm. It was indicated that LCI is a good index to quantify the effect of lateral sediment connectivity of landslides on sediment yield in the catchment and that landslides generated by heavy rainstorms have long-term impacts on sediment transport processes in the slope-channel cascades of the catchment. Regarding slope management, we propose to protect gully slopes by reducing lateral sediment connectivity between upslope areas and gully slopes and to protect terrace slopes by constructing boundary dikes and drainage ditches to reduce slope collapse under heavy rainstorms.