A review of concentrated flow erosion processes on rangelands: Fundamental understanding and knowledge gaps

Nouwakpo, Sayjro K.; Williams, Christopher J.; Al‐Hamdan, Osama Z.; Weltz, Mark A.; Pierson, Frederick B.; Nearing, M. A.

doi:10.1016/j.iswcr.2016.05.003

Cited by 62 publications

(33 citation statements)

References 123 publications

(206 reference statements)

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“…Gully growth intensity depends clearly on the relief unit. Thus, we can confirm the idea that leads to the formation of Erosion Response Units Although many authors have noted their importance, the contribution of rills to total soil erosion has been intensely discussed for decades (e. g. Auzet et al, 1993;Cerdan et al, 2002;Nouwakpo et al, 2016b). But their development, dynamics and generation processes are still not understood in their entirety and complexity (e. g. Govers et al, 2007;Wirtz et al, 2013b).…”

Section: Discussionsupporting

confidence: 80%

“…The development of these rills may increase erosion rates to an order of magnitude higher than erosion caused by non-concentrated surface flows (Cerdan et al, 2002;Merz and Bryan, 1993;Nouwakpo et al, 2016b;Poesen, 1987;Wirtz et al, 2012a). Because of their highly erratic appearance and their easy destruction through soil management, erosion processes in rills are difficult to quantify (Casalí et al, 2006;Nouwakpo et al, 2016a;Wells et al, 2016).…”

Section: Rill Erosionmentioning

confidence: 99%

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Erosion processes on different relief units: the relationship of form and process

Iserloh

Wirtz

Seeger

et al. 2017

CIG

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Section: Discussionsupporting

confidence: 80%

Section: Rill Erosionmentioning

confidence: 99%

Erosion processes on different relief units: the relationship of form and process

Iserloh

Wirtz

Seeger

et al. 2017

CIG

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“…Hydraulic friction factors, such as Chezy and Manning coefficients, are commonly used on runoff models for stony rangeland (and other) soils (Nouwakpo et al, 2016), but this usage is problematic because the coefficients depend on slope gradient and runoff rates, and hence with distance downslope on the hill and time during the runoff event. The data clearly showed that there was no unique hydraulic coefficient for a given surface condition.…”

Section: Discussionmentioning

confidence: 99%

Slope–velocity equilibrium and evolution of surface roughness on a stony hillslope

Nearing

Polyakov

Nichols

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Slope-velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5, 12, and 20 % slope gradients. A series of simulations were made with two replications for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was no unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope-velocity equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope-scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

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“…The interaction among rill flow, the erodible wetted perimeter, and sediment transport affects rill morphology and limits the applicability of the uniform flow equation developed for large and fixed beds (i.e., Chezy's and Manning's equation). Notwithstanding these differences, Chezy's equation is usually applied in soil erosion models (Ferro, 1999;Govers et al, 2007;Nouwakpo et al, 2016;Powell, 2014;Strohmeier, Nouwakpo, Huang, & Klik, 2014).…”

Section: Introductionmentioning

confidence: 99%

Rill flow resistance law under equilibrium bed‐load transport conditions

Stefano

Nicosia

Pampalone

et al. 2019

Hydrological Processes

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In this paper, a recently deduced flow resistance equation for open channel flow was tested under equilibrium bed‐load transport conditions in a rill. First, the flow resistance equation was deduced applying dimensional analysis and the incomplete self‐similarity condition for the flow velocity distribution. Then, the following steps were carried out for developing the analysis: (a) a relationship (Equation ) between the Γ function of the velocity profile, the rill slope, and the Froude number was calibrated by the available measurements by Jiang et al.; (b) a relationship (Equation ) between the Γ function, the rill slope, the Shields number, and the Froude number was calibrated by the same measurements; and (c) the Darcy–Weisbach friction factor values measured by Jiang et al. were compared with those calculated by the rill flow resistance equation with Γ estimated by Equations and . This last comparison demonstrated that the rill flow resistance equation, in which slope and Shields number, representative of sediment transport effects, are introduced, is characterized by the lowest values of the estimate errors.

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A review of concentrated flow erosion processes on rangelands: Fundamental understanding and knowledge gaps

Cited by 62 publications

References 123 publications

Erosion processes on different relief units: the relationship of form and process

Erosion processes on different relief units: the relationship of form and process

Slope–velocity equilibrium and evolution of surface roughness on a stony hillslope

Rill flow resistance law under equilibrium bed‐load transport conditions

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