Upslope sediment-laden flow impacts on ephemeral gully erosion: evidences from field monitoring and laboratory simulations

Authors: XU, XIMENG - Northwest Agricultural & Forestry University; ZHENG, FENLI - Northwest Agricultural & Forestry University; TANG, QIUHONG - Chinese Academy Of Sciences; WILSON, GLENN - Retired ARS Employee; WU, MIN - Shenyang Agricultural University; HAN, YONG - Ankang University; XIAO, PEIQING - Yellow River Institute Of Hydraulic Research; Zhang, Xunchang

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2021
Publication Date: 10/20/2021
Citation: Xu, X., Zheng, F., Tang, Q., Wilson, G.V., Wu, M., Han, Y., Xiao, P., Zhang, X.J. 2021. Upslope sediment-laden flow impacts on ephemeral gully erosion: evidences from field monitoring and laboratory simulations. Catena. 209:105802. https://doi.org/10.1016/j.catena.2021.105802.
DOI: https://doi.org/10.1016/j.catena.2021.105802

Interpretive Summary: Upslope sediment-laden flow impacts ephemeral gully erosion processes. Ephemeral gullies are an important linear erosion feature in many agricultural fields, often occurring at a mid-slope field position that can be greatly influenced by upslope inflow. Field monitoring on the natural hillslope and indoor simulations demonstrated that additional erosion occurs by the introduction of upslope, sediment laden inflows. Field monitoring results also showed that the largest impact of upslope sediment-laden flow on downslope ephemeral gully erosion was usually found in July when extreme rainfall events occurred and when a large proportion of the annual sediment yield is produced. This study illustrated the importance of field monitoring and indicated that design of indoor simulation experiments needs more comprehensive considerations on complicated hydrological and sediment conditions.

Technical Abstract: Ephemeral gully (EG) is an important linear erosion feature, often occurring at mid-slope position, that can be greatly influenced by upslope inflow and its sediment transport capacity. How sediment concentration in upslope inflow influences downslope EG erosion is still unclear. Thus, field monitoring on a natural hillslope and indoor simulations on a dual-box system were conducted to better understand their relationships. The results showed that both field monitoring and indoor simulation displayed additional erosion caused by upslope inflow and sediment load, verifying the transport-dominated sediment regime in EG systems. In field observations, the sediment increment coefficient (SIC) on an event scale varied from 4.6% to 88.6%. In indoor simulations, the SIC changed from 24.9% to 87.5%, demonstrating net erosion induced by upslope run-on sediment-laden flow. Meanwhile, great differences were found between field monitoring and indoor simulations regarding the sediment concentration impact on EG erosion. Indoor simulation experiments with a range of 0-400 g L-1 sediment concentration supplied by a feeder box, showed that SIC linearly decreased as sediment concentration of upslope inflow increased. While under natural field monitoring conditions, rainfall events with PI30 larger than 400 mm h-1 (similar to the designed extreme rainfall in laboratory simulations), exhibited a quadratic relationship between SIC and sediment concentration of upslope inflow. The minimum SIC occurred when sediment concentration of upslope inflow was around 413 g L-1. Thus, indoor simulations only partial verified the complicated natural phenomenon. This study illustrated the importance of field in situ monitoring and indicated that design of indoor simulation experiments needs more comprehensive considerations on complicated hydrological and sediment conditions in future.