Interactive effects of raindrop impact and groundwater seepage on soil erosion

Authors: LIU, GANG - Northwest Agricultural & Forestry University; ZHENG, FENLI - Northwest Agricultural & Forestry University; JIA, LU - Northwest Agricultural & Forestry University; JIA, YAFEI - University Of Mississippi; Zhang, Xunchang; HU, FEINAN - Northwest Agricultural & Forestry University; ZHANG, JIAQIONG - Northwest Agricultural & Forestry University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2019
Publication Date: 8/21/2019
Citation: Liu, G., Zheng, F., Jia, L., Jia, Y., Zhang, X.J., Hu, F., Zhang, J. 2019. Interactive effects of raindrop impact and groundwater seepage on soil erosion. Science of the Total Environment. 578. https://doi.org/10.1016/j.jhydrol.2019.124066.
DOI: https://doi.org/10.1016/j.jhydrol.2019.124066

Interpretive Summary: The soil water seepage and raindrop impact play important roles in soil erosion in fields. However, reliable quantification of the effects is not yet done. Therefore, a laboratory study was conducted to reveal the effects of raindrop impact and artesian seepage on hillslope erosion. A soil box (5.0 m long, 0.5 m wide, and 0.5 m deep) was subjected to rainfall simulation experiments under free drainage and seepage conditions. The results indicated that compared with no raindrop impact under screen cover (simulating plant canopy), raindrop impact increased the runoff rate, sediment delivery and sediment concentration in about 3.1-14.3%, 73.6-695.8%, and 64.2-560.0%, respectively. Compared with well drained soil, seepage increased sediment delivery and concentration about 70.2-588.2% and 27.3-411.1%, respectively. The power function relations were found between sediment delivery and runoff rate. The increasing rates of sediment yields per unit increase in runoff were greatest for the case of seepage with raindrop impact, least for free drainage without drop impact, and intermediate the other combinations. In addition, the mean size of aggregates was reduced in the erosion events by about 50% because of the aggreagate breakdowns by raindrop impact or slaking. The loss of <0.25 mm aggregate accounted for 76.5-98.2% of the total aggregate loss in all treatments. These results would be useful to soil and water conservationists to control erosion by improving surface cover and soil drainage.

Technical Abstract: The seepage and raindrop impact (RI) play important roles in soil erosion processes. However, reliable quantification of their relationships to the erosion processes is not yet clear. Therefore, a laboratory study was conducted to reveal the effects of RI and artesian seepage (AS) on hillslope erosion. A soil box (5.0 m long, 0.5 m wide, and 0.5 m deep) was subjected to rainfall simulation experiments under free drainage (FD) and AS conditions. The effect of RI was studied by dissipating raindrop energy (WRI). The results indicated that compared with WRI, RI increased the runoff rate, sediment delivery and sediment concentration in about 3.1-14.3%, 73.6-695.8%, and 64.2-560.0%, respectively. With a higher runoff rate of 27.4-54.3%, AS increased sediment delivery and concentration about 70.2-588.2% and 27.3-411.1%, respectively. The power function relations were found between sediment delivery and runoff rate. The increasing rate of sediment yields per unit increase in runoff followed the order: AS-RI > FD-RI > AS-WRI > FD-WRI. The sediment regime seemed to be detach-limited in most cases. As a result of seal formation, RI, compared with WRI, had marginally enhanced the average flow velocity and shear stress, and reduced the resistance coefficient. The effects of AS on flow-hydraulic parameters were more pronounced than RI due to added runoff by seepage. The mean size of aggregates was reduced in the processes by about 50% because of breakdown by raindrop impact or slaking. The loss of <0.25 mm aggregate accounted for 76.5-98.2% of the total aggregate loss in all treatments.