Exploring rainfall kinetic energy induced erosion behavior and sediment sorting for a coarse-textured granite derived soil of south China

Authors: NI, SHIMIN - Huazhong Agricultural University; ZHANG, DEQIAN - Huazhong Agricultural University; CAI, CHONGFA - Huazhong Agricultural University; Wilson, Glenn; ZHANG, JIANHUA - Huazhong Agricultural University; WANG, JUNGUANG - Huazhong Agricultural University

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2020
Publication Date: 12/25/2020
Citation: Ni, S., Zhang, D., Cai, C., Wilson, G.V., Zhang, J., Wang, J. 2020. Exploring rainfall kinetic energy induced erosion behavior and sediment sorting for a coarse-textured granite derived soil of south China. Soil & Tillage Research. 208:104915. https://doi.org/10.1016/j.still.2020.104915.
DOI: https://doi.org/10.1016/j.still.2020.104915

Interpretive Summary: The kinetic energy (KE) of rainfall, which is the energy of rainfall due to its rate of fall and mass of the drops, is one of the primary indicators of the erosive power of raindrops. A better understanding of the effects of rainfall KE on soil loss and the sorting of different size particles in the sediment eroded will contribute to improved erosion and sediment prediction. In this paper, we focus on the effects of rainfall KE on runoff rate, soil loss, and the particle size distribution (PSD) of eroded sediment in a coarse-textured sandy loam soil with three different horizons (topsoil horizon, illuvial horizon, parent material horizon) exposed on the surface. A series of rainfall simulation experiments were conducted in a 0.8 m by 3 m flume on steep slopes (16.7%). Each rainfall was applied at a constant intensity of 90 mm h¬-1 for 1 h. Raindrops reaching the soil surface were simulated to be under five rainfall KEs (628, 443, 324, 231, and 110 J m-2 h-1) by covering the soil surface with wire screens with different size openings that intercepted the rainfall. Runoff and sediment were sampled at 3-min intervals to measure runoff rate, soil erosion rate and sediment PSD. These data were used to determine rainfall KE on soil loss and sediment sorting. The increase in KE and depth of the soil horizon exposed had positive effects on runoff rate and soil erosion rate, with the topsoil having the strongest erosion resistance. A linear relationship could describe the relationships between soil erosion rate and KE (or stream power). The percentage of clay- and silt-sized particles in sediment decreased with increasing KE and runoff duration, whereas sand- and gravel-sized particles increased with KE and duration. As a result, the enrichment of fine particles in runoff produced a coarsening or “armoring” of the slope surface, which may affect subsequent erosion in field. The loss of clay- and silt-sized particles by erosion in these coarse-textured soils emphasizes the importance of sediment sorting to transport. The findings reported in this study suggests that the relationship of rainfall KE to erosion is required to practically and effectively estimate and predict the potential erosiveness of rainstorms.

Technical Abstract: Rainfall kinetic energy (KE) is one of the primary indicators of rainfall erosivity. A better understanding of the effects of rainfall KE on soil loss and sediment sorting will contribute to improved erosion and sedimentation prediction. In this paper, we focus on the effects of rainfall KE on runoff rate, soil loss, and the particle size distribution (PSD) of eroded sediment in a coarse-textured sandy loam soil with three horizons (topsoil horizon, illuvial horizon, parent material horizon). A series of rainfall simulation experiments were conducted in a 0.8 m by 3 m flume on steep slopes (16.7%), and each rainfall lasted for 1 h under five rainfall KEs (628, 443, 324, 231, and 110 J m-2 h-1), which were obtained by covering the soil surface with wire screens with different apertures that intercepted simulated rainfall at an intensity of 90 mm h¬-1. Runoff and sediment were sampled at 3-min intervals to measure runoff rate, soil erosion rate and sediment PSD. These data were used to interpret rainfall KE on soil loss and sediment sorting. The increase in KE and soil horizon had positive effects on runoff rate and soil erosion rate, and the topsoil had strong erosion resistance. The linear relationship could describe the relationships between soil erosion rate and KE (or stream power). The percentage of clay- and silt-sized particles in sediment decreased with increasing KE and runoff duration, whereas sand- and gravel-sized particles were the opposite. As a result, the enrichment of fine particles in runoff produced a coarsening or “armoring” of the slope surface, which may affect subsequent erosion in field. The observed large preferential loss of clay- and silt- sized particles by erosion in these coarse-textured soils emphasizes the importance of sediment sorting to transport. The findings reported in this study suggests that the relationship of rainfall KE to erosion is required to practically and effectively estimate and predict the potential erosiveness of rainstorms.