Multi-temporal spatial modelling to assess runoff and sediment dynamics under different microtopographic patterns

Abstract

Soil erosion is a multi-scale geographical interface process with high spatiotemporal variability. This study aimed to assess runoff and sediment dynamics under different microtopographic patterns based on wavelet analysis and SIMulated Water Erosion model (SIMWE). Three rainfall intensities of 1.0 mm min−1, 1.5 mm min−1, and 2.0 mm min−1, combined with three slope gradients of 10°, 15°, and 20°, were utilized to conduct rainfall simulations on three soil boxes measuring 4 m in length and 0.8 m in width. The soil boxes exhibited distinct microtopographic patterns, including smooth slope (CK), artificial digging (AD), and ridge tillage (RT). The results showed that the runoff and sediment reduction benefits of different tilled slopes decreased with an increase in both slope and rainfall intensity. The AD and RT slopes reduced runoff yields by 8.4% − 50.2% and 17.3% − 75.0% respectively compared to CK slope. Although sediment yields from AD and RT slopes were reduced by 4.2% − 51.6% and 1.8% − 53.0%, respectively, the sediment control benefits of AD and RT slopes were basically lost when the slope gradient increased to 20°. The rill erosion was the main source of soil erosion on different tilled slopes, accounting for 72% − 87% of the total soil loss. And the rates of both soil erosion and rill erosion exhibited a power function relationship with an increase in rainfall intensity and slope. The impact of slope gradient on soil erosion on the RT slope was greater than those on the CK and AD slopes. During the development of rill erosion, non-stationary and multi-scale periodic phenomena exist in the time series of runoff and sediment on different microreliefs. As surface microrelief increased, the fluctuations in runoff and sediment on tilled slopes intensified, resulting in a gradual shortening of the variation period. And this study verified the feasibility of the SIMWE model to simulate the runoff and sediment dynamics on microtopographic scale under a single rainfall event. The results can provide a theoretical basis for the scientific layout of soil and water conservation practices in sloping farmland and the construction of soil erosion model in purple soil area.