Spatio-temporal evolution characteristics and driving factors of water erosion under microtopography

Abstract

ΔDEM (Digital Elevation Model) accurately quantifies topographic changes, such as erosion and sedimentation. Previous research on micro-topographic water erosion largely relies on DEMs, which lack a temporal dimension and do not effectively capture erosion dynamics. This study aims to analyse the spatial patterns and evolutionary processes of micro-topographic water erosion. Specifically, artificial rainfall experiments were designed and conducted on a 15° Artificial Digging (AD) slope, employing M-ΔDEM to quantify erosion pattern indicators and further investigate the key influencing factors. Results indicate distinct erosion morphology and spatial patterns on tilled slopes. Erosion evolves into a tree-like structure, with detachment and transportation primarily in the upper slope and lateral deposition in the lower slope. Increased rainfall intensity reduces erosion fragmentation, enhances patch connectivity, and broadens the impact area. Topographic factors have a more significant influence on soil erosion than rainfall factors, with their importance (in descending order) and primary value ranges as follows: surface roughness (1.0 to 1.25), topographic index (0.3 to 1.3 mm), surface relief (0 to 10 mm), Micro-slope gradient (0 to 40°), surface incision depth (0 to 5 mm), slope ratio (0.20 to 0.75), and surface depression volume (−20 to 20 mm³). M−slope gradient and surface depression volume show a linear relationship with sediment yield, while other factors exhibit less clear relationships. Sensitivity to topographic factors shifts from the slope edge to the centre. This study recommends that adjustments to surface roughness and M−slope gradient at the left and right edges of loess slopes can effectively mitigate soil erosion when implementing agricultural measures. Additionally, it reveals the spatial patterns of erosion evolution and the key influencing factors, contributing to the management and conservation of agricultural practices on loess slope.