Erosion processes and features for a coarse-textured soil with different hoizons: a laboratory simulation

Authors: NI, SHIMIN - Huazhong Agricultural University; ZHANG, DEQIAN - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A; WEN, HUI - Huazhong Agricultural University; CAI, CHONGFA - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A; Wilson, Glenn; WANG, JUNGUANG - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A

Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2020
Publication Date: 5/28/2020
Citation: Ni, S., Zhang, D., Wen, H., Cai, C., Wilson, G.V., Wang, J. 2020. Erosion processes and features for a coarse-textured soil with different hoizons: a laboratory simulation. Journal of Soils and Sediments. 2020 pp. 1-16. https://doi.org/10.1007/s11368-020-02665-5.
DOI: https://doi.org/10.1007/s11368-020-02665-5

Interpretive Summary: Soil erosion is a main cause of land degradation and exposes subsurface layers at the surface which can impact future erosion. A deeper understanding of the soil erosion processes and landscape features from past erosion can help in the assessment and prediction of future erosion. This work investigated the effects of rainfall intensity and inflow from upslope on the runoff, soil loss and erosion features of soils with different degrees of past erosion. To achieve the objectives, a series of laboratory experiments were conducted in a flume using two rainfall intensities (90 and 120 mm h-1) combined with two inflow rates (2 and 2.66 L min-1) on three layers of coarse-textured soil that were exposed at the surface by past erosion. Runoff and soil loss corresponded to shifts in the erosion phase from sheet, to rill advancement to mature rill stages. Increase in rainfall-inflow rates played a positive role whereas and the content of coarse grains on the surface played a negative role in the the rate of sediment loss. Headcut erosion of rills and rill density increased with increasing rainfall intensity and were worse for the soils with greater past erosion which exposed deeper layers at the surface. Slope roughness increased with time due to rill formation and its interaction with soil properties and rainfall characteristics was highly variable. Moreover, the surface of the slopes were enriched with coarse grains with time due to erosion of the fine particles during later stages of erosion. The coarse grains content of the surface had a beneficial effect on the sediment loss rate and rill advancement rate by providing surface armoring. These results proved that the topsoil in interrill areas was less erodible after the surface was enriched in coarse grains but the secondary effect was a potential worsening of rill erosion. This work will assist soil conservationists in understanding the magnitude of future erosion caused by exposure of subsurface layers at the surface by past erosion and the changes to expect in the main mechanisms from sheet to rill erosion processes. Additionally, it helps conservationist assess the importance of enrichment of sands and gravels on the surface in interrill areas providing an armoring effect against further sheet erosion and the need to apply conservation practices to protect hillslopes from the subsequent shift to greater rill erosion. Furthermore this work provide a reference for restoration of landscapes affected by past erosion, especially bare lands.

Technical Abstract: Soil erosion is a main mechanism of land degradation. A deeper understanding of the soil erosion processes and features with various erosive forces can help to assess and predict erosion. This work investigated the effects of rainfall intensity and inflow rate on the runoff, soil loss and erosion features of soils with different erosion degrees on steep slopes. To achieve the objectives, a series of laboratory simulation tests were conducted in a 0.8 m by 3 m flume using two rainfall intensities (90 and 120 mm h-1) and two inflow rates (2 and 2.66 L min-1) on a coarse-textured soil with three soil horizons. Runoff and soil loss corresponded to the evolution of soil erosion phase. Increase in rainfall-inflow played the positive roles in sediment load rate (p < 0.01). For the erosion features of slope, the headward erosion rate and rill density degree increased with increasing rainfall/inflow rate and erosion degree of soil. Although the slope roughness showed heterogeneity for different rainfall-inflow treatments, the topsoil (slight erosion degree) exhibited weak soil erodibility. Moreover, the coarse grains showed obvious enrichment on the slope surface, which formed an armoring on the slope surface. Coarse grains content of soil had a negative effect on sediment load rate (r = -0.76, p < 0.01) and rill advancement rate (r = -0.87, p < 0.01). These results proved that the surface coarse grains has a significantly protective effect. The results of this work can be used to clarify the magnitude of expected in coarse-textured soils and provide a reference for bare land restoration following serious erosion.