Characterizing detachment and transport processes of interrill soil erosion

• Published in: Geoderma Vol. 376; p. 114549
• Main Authors: Zhang, X.C. (John), Zheng, F.L., Chen, J., Garbrecht, J.D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2020
• Subjects: Flow-driven transport; Interrill erosion modeling; Interrill erosion process; Raindrop detachment; Raindrop-driven transport; Sheet flow detachment; Raindrop-driven transport; RD; Raindrop detachment; Flow-driven transport; RDT; Interrill erosion modeling; FDT; Sheet flow detachment; Interrill erosion process; FD
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2020.114549

A novel experimental protocol was used to characterize interrill erosion processes in both detachment-limiting and transport-limiting regimes. Small soil columns under tiny rocks marked with red crosses in the photo indicated that raindrop-impacted sheet flow seemed capable of detaching soil in the detachment-limiting regime probably because of the turbulence caused by raindrop impact. Raindrop-driven and flow-driven sediment transport were quantified for the first time. Stream power and a multiplicative empirical equation could be used to predict interrill sediment delivery for all erosion regimes precluding the need to develop different sets of predictive equations for each regime. [Display omitted] •Raindrop-impacted sheet flow seems capable of detaching soil in interrill erosion.•A novel protocol was proposed to partition raindrop-driven and flow-driven transport.•Stream power and an empirical Eq. were best predictors for interrill sediment discharge.•Both equations can predict sediment discharge for all interrill erosion regimes. Detachment and transport processes of interrill soil erosion are not yet fully understood and quantified due to their complexity. Understanding these processes and their interaction is essential to developing effective interrill erosion prediction models. Thus, the objectives are to (1) identify detachment-limiting and transport-limiting regimes by comparing measured total soil splash with total sediment load of flow wash, (2) estimate relative importance of raindrop-driven and flow-driven transports under selected flow conditions using a novel experimental protocol, and (3) test widely used erosion equations for use in both detachment-limiting and transport-limiting regimes under the experimental conditions never before used. Sediment discharge and raindrop splash were separately collected from two plots with a 2.5-cm gap between them. Three rainfall intensities of 60, 90, and 120 mm h−1 were applied to three slopes of 9, 18, and 27% under two cover treatments of screen and tarp. Screen cover is to simulate crop canopy for dissipating raindrop energy, which is to control upslope sediment inflow by reducing raindrop detachment without modifying runoff rates. Tarp cover is to control both water and sediment inflows by varying slope length. Results showed that total raindrop splash in the entire plot during an event was less than total flow wash in the screen treatment, indicating detachment-limiting scenarios. However, total raindrop splash was greater (less) than total wash at the 9% (27%) slope in the tarp treatment, indicating transport-limiting (detachment-limiting) cases. The results indicated that raindrop-impacted flow might be able to detach soil in some cases. This finding runs counter to the common wisdom that soil detachment in interrill erosion is solely caused by raindrop impact. If raindrop-impacted flow can detach soil, the determination of limiting process by direct comparison between splash and wash loads seemed overly simplistic. Raindrop-driven transport was estimated for the first time by a means of dissipating raindrop impact energy in this study. Raindrop-driven transport was found to increase with rainfall intensity and slope gradients. Stream power and an empirical multiplication-of–factor equation performed well in predicting interrill sediment delivery under all erosion regimes, suggesting that it is unnecessary to develop distinct predictive equations for different interrill erosion regimes.