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Effect of raindrop splash and transversal width on soil erosion: laboratory flume experiments and analysis with the Hairsine–Rose model


Jomaa, Seifeddine; Barry, D A; Brovelli, Alessandro; Sander, Graham C; Parlange, Jean-Yves; Heng, B C P; Tromp-van Meerveld, H J (2010). Effect of raindrop splash and transversal width on soil erosion: laboratory flume experiments and analysis with the Hairsine–Rose model. Journal of Hydrology, 395(1-2):117-132.

Abstract

The parameter consistency of the one-dimensional Hairsine–Rose (H–R) erosion model under conditions of significant rainfall splash was examined. To account for the splash characteristic length scale and its interaction with the transverse erosion width, experiments were carried out using erosion flumes of the same length (6 m), but different widths, with sediment concentrations measured at the flume exits. Total sediment concentration and the concentration of seven size fractions (<2, 2–20, 20–50, 50–100, 100–315, 315–1000 and >1000 μm) were measured at high rainfall intensity (60 mm h−1) and with a gentle slope (2.2%). The conditions employed ensured that erosion was predominantly precipitation-driven. The experimental results showed that raindrop splash affected particularly the sediment breakthrough from the wider flumes (flumes 1 and 2, 1- and 0.5-m wide, respectively). However, the raindrop splash effect was less significant in observed sediment concentrations from the narrower flumes (flumes 3 and 4, both 0.25-m wide). For these flumes, the detached sediment was affected by the transversal width of the flume in that an amount of detached sediment adhered to the barriers instead of being removed in the overland flow. The one-dimensional H–R model was fitted to the experimental results and good agreement was found, in particular for the finer size classes. The data for the coarser grain sizes were more scattered, suggesting sediment motion by mechanisms other than suspension in the overland flow (e.g., rolling along the soil surface). The optimized parameters indicated that the shield layers (where the shield consists of re-deposited eroded sediment) of the wider flumes (1 and 2) developed within 5–10 min from the start of the experiment, whereas in the narrower flumes (3 and 4) they never fully developed. The optimized detachment rates were consistent with previous findings, but the estimated thickness of the deposited layer was too small to provide complete protection of the original soil against raindrop detachment, indicating that the shield was not uniform. The experimental design allowed us to investigate directly the effect of flow non-uniformity on soil erosion by inclusion of an offset drainage point in flume 4. The observations taken during and after the experiment, as well as surface elevation data, confirmed the noticeable impact of non-uniform flow on the erosion process.

Abstract

The parameter consistency of the one-dimensional Hairsine–Rose (H–R) erosion model under conditions of significant rainfall splash was examined. To account for the splash characteristic length scale and its interaction with the transverse erosion width, experiments were carried out using erosion flumes of the same length (6 m), but different widths, with sediment concentrations measured at the flume exits. Total sediment concentration and the concentration of seven size fractions (<2, 2–20, 20–50, 50–100, 100–315, 315–1000 and >1000 μm) were measured at high rainfall intensity (60 mm h−1) and with a gentle slope (2.2%). The conditions employed ensured that erosion was predominantly precipitation-driven. The experimental results showed that raindrop splash affected particularly the sediment breakthrough from the wider flumes (flumes 1 and 2, 1- and 0.5-m wide, respectively). However, the raindrop splash effect was less significant in observed sediment concentrations from the narrower flumes (flumes 3 and 4, both 0.25-m wide). For these flumes, the detached sediment was affected by the transversal width of the flume in that an amount of detached sediment adhered to the barriers instead of being removed in the overland flow. The one-dimensional H–R model was fitted to the experimental results and good agreement was found, in particular for the finer size classes. The data for the coarser grain sizes were more scattered, suggesting sediment motion by mechanisms other than suspension in the overland flow (e.g., rolling along the soil surface). The optimized parameters indicated that the shield layers (where the shield consists of re-deposited eroded sediment) of the wider flumes (1 and 2) developed within 5–10 min from the start of the experiment, whereas in the narrower flumes (3 and 4) they never fully developed. The optimized detachment rates were consistent with previous findings, but the estimated thickness of the deposited layer was too small to provide complete protection of the original soil against raindrop detachment, indicating that the shield was not uniform. The experimental design allowed us to investigate directly the effect of flow non-uniformity on soil erosion by inclusion of an offset drainage point in flume 4. The observations taken during and after the experiment, as well as surface elevation data, confirmed the noticeable impact of non-uniform flow on the erosion process.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2010
Deposited On:22 May 2015 14:23
Last Modified:05 Apr 2016 19:15
Publisher:Elsevier
ISSN:0022-1694
Publisher DOI:https://doi.org/10.1016/j.jhydrol.2010.10.021

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