Impacts of Lidar-Derived Dem Resolution on Erosion Rate Modelling in the Hilly and Gully Loess Plateau

Abstract

The resolution of Digital Elevation Model (DEM) plays a critical role in determining the slope steepness and slope length, —which critically influence the simulation outcomes of various erosion models. Previous studies have typically overlooked the process of sediment transport and the spatial variability of sediment deposition, particularly at ultra-high resolution levels. This study utilized Unmanned Aerial Vehicles (UAV) Light Detection and Ranging (LiDAR) to capture high-resolution DEMs and spatial erosion and deposition validation data within the Qiaogou catchment situated in the hilly and gully Loess Plateau. The Water and Tillage Erosion Model and Sediment Delivery Model (WaTEM/SEDEM) was then employed to simulate soil erosion and deposition across varying DEM resolutions. The investigation looked at the impacts of DEM resolutions on topographic factors and their subsequent impact on soil erosion simulations across different geomorphic units, including hillslopes, gully slopes, and channels. Results showed that 1) a decrease in DEM resolutions led to a reduction in average slope gradient and an increase in slope length, LS factor, and volumes of soil erosion and deposition, with sediment yield first increasing and then decreasing. 2) The spatial patterns of erosion and deposition simulated across DEM resolutions ranging from 0.1 m to 10 m showed a moderate consistency with those simulated at 3 m resolution, deteriorating as the resolution deviates further from this benchmark. 3) The impacts of DEM resolution on slope gradient, slope length, LS factor, soil erosion volume and sediment yield were greater at a catchment scale than those on hillslopes but less than those on gully slopes. However, the impacts on deposition were reversed. This research contributed valuable insights into the impact of high-resolution DEMs on the modeling of soil erosion, deposition, and sediment yield in distinct geomorphic areas.

Keywords: Laser scanning, Photogrammetry, Geomophic units, Erosion-transport-deposition, WaTEM/SEDEM