Overland Flow Conditions Research Articles

Vegetative Flow Resistance for Erosion Control Using Grass Species from the Caribbean Region

Vegetative channels convey runoff effectively, prevent flooding, protect soil against erosion, avoid the formation of gullies, maintain adequate water quality, and reduce the generation of sediments. The degree of retardance as a measure of the drag force on the vegetation cover is a crucial parameter for determining resistance to water flow in these channels. This research developed a new procedure to assess Manning’s coefficient and retardance index for vegetation using four Caribbean Area grass species: Bahía Grass (Paspalum notatum), Zoysia Grass (Zoysia sp.), Pangola Grass (Digitaria eriantha), and Bermuda Grass (Cynodon dactylon). The USDA-NRCS Caribbean Area identified 16 species as vegetative lining for waterways and proposed a classification according to the degree of vegetative retardance. The category for these species was developed for use in the Western Gulf Region and required validation for the Caribbean region. A modified universal log law fitted the velocity distributions above the vegetative lining in the experiments. The energy equation for a gradually varied flow, the momentum equation, and Manning’s equation provided a solution for Manning’s coefficient. The procedure allowed us to assign a degree of retardance to the species obtained by comparing Manning’s coefficients with those from USDA-NRCS. Results show that retardance degrees published in the Puerto Rico Erosion and Sedimentation Control Handbook for Developing Areas apply to the species tested in this project. This research identified a new retardance degree for Pangola grass when the plant height is less than 0.15 m. The experimental values for Manning’s coefficient are also recommended for use in overland flow conditions.

The Functional Relationship of Sediment Transport under Various Simulated Rainfall Conditions

Sediment removed in the detachment process is transported by overland flow. Previous experimental and field works studied that sediment transport is influenced by hydraulic properties of flow, physical properties of soil, and surface characteristics. Several equations in predicting sediment transport have been developed from previous research. The objective of this paper was to establish the selected parameters that contribute to the sediment transport capacity in overland flow conditions under different rainfall pattern conditions and to evaluate their significance. The establishment of independent variables was performed using the dimensional analysis approach that is Buckingham’s π theorem. The final results obtained are a series of independent parameters; the Reynolds number (Re), dimensionless rainfall parameter iLν, hydraulic characteristics QLν that related to the dependent parameters; and dimensionless sediment transport qsρv. The relationship indicates that 63.6% to 72.44% of the variance in the independent parameters is in relation to the dependent parameter. From the iteration method, the estimation of constant and regression coefficient values is presented in the form of the general formula for linear and nonlinear model equations. The linear and nonlinear model equations have the highest model accuracy of 93.1% and 81.5%, respectively. However, the nonlinear model equation has the higher discrepancy ratio of 54.9%.

Impacto de la cobertura vegetal en la erosión-deposición del suelo por efecto de escorrentía superficial

Introduction: In arid regions, soil losses are caused by torrential rainfall events and by the erosive energy of runoff. Objectives: To quantify the impact of the use of different types of vegetation cover on soil erosion and soil deposition caused by overland flow. Methodology: The experiment was carried out from July to September 2017 under a randomized block experimental design with three replications. The treatments evaluated were maize harvest residues and buffel grass (Cenchrus ciliaris L.) sowing (MHR + G), maize harvest residues (MHR), buffel grass sowing (G), and the control (C). Results: The MHR + G treatment reduced erosion by 44 % (26.3 t·ha-1) compared to the control (58.6 t·ha-1). Soil deposition was 47.6 and 51.7 t·ha-1 with MHR + G and G, respectively, while in C was 26.1 t·ha-1. Limitations of the study: The results found are valid for the soil and water conditions of this study Originality: There are few technical and scientific reports on the behavior of soil particle removal and deposition processes under runoff conditions. Conclusions: The layer thickness of soil removed and deposited, under overland flow conditions, depends on the type of soil cover. The MHR + G treatment significantly reduced soil erosion, making it a viable alternative.

Effects of bed roughness on a horseshoe vortex in overland water flowing past a cylinder

A horseshoe vortex (HV) system is formed around a bed-mounted circular cylinder in overland water flowing past the cylinder; however, the effect of bed roughness on HV still lacks clear recognition. The present study experimentally investigated the characteristics of HV upstream of a bed-mounted circular cylinder in a flume, where sand of four grain sizes was glued to the flume bed to produce the bed roughness. A particle image velocimetry system was mounted on the flume to facilitate a high-resolution (63 pixel/mm) observation of a flow field. A total of 28 cases with flow depths varying from 0.39 to 1.09 cm and cylinder Reynolds numbers (ReD) varying from 2700 to 5800 were selected to evaluate the effects of the bed roughness on HV in overland flow conditions. Measurements were then conducted on the upstream flow of a cylinder in the symmetry plane. Bed roughness significantly affected HV, in turn destroying the three vortices. Subsequently, time-averaged primary HV features on the three beds with lower roughness levels were analyzed in terms of the separation point, location, radius, and swirling strength. With an increase in the bed roughness, the separation point moved toward the cylinder, and the primary HV moved toward a free surface; however, the effect on the streamwise location was nonsignificant. A positive relationship was observed between the radius of the primary HV and the bed roughness, whereas a negative relationship was observed between the swirling strength and bed roughness. For beds with the highest roughness levels, all vortices were destroyed, and there was no clear HV topology in the time average sense. Finally, the motion process of the HV was summarized as showing an increase in the bed roughness. The present study investigated HV features with different bed roughness levels and has the potential to enhance our theoretical understanding of the relationship between HV kinematic characteristics and the bed roughness.

Tillage and Liquid Dairy Manure Effects on Overland Flow Nitrogen and Phosphorus Loss Potential in an Upper Midwest Corn Silage-Winter Triticale Cropping System

Dairy manure is an important crop nutrient source in Wisconsin and other parts of the upper Midwest but can contribute to nitrogen (N) and phosphorus (P) losses in overland flow/surface runoff. Winter cereal grain cover crops can help reduce erosion and nutrient transport in corn systems. However, few studies have compared tillage impacts on nutrient loss in live cover crop systems. The objective of this study was to evaluate vertical (VT) and chisel tillage (CT) effects on overland flow nutrient and sediment loss potential after spring-applied liquid manure. A surface application treatment (i.e., broadcast) and a no manure control were also included for comparison. After corn (Zea mays L.) planting into a live triticale (Triticale hexaploide L.) cover crop, four artificial rainfall-overland flow events were generated (42 mm h−1 for 30 min) on replicated field-scale plots in central Wisconsin. Mean total P, total N, and suspended solids loads were consistently lower for VT at 2 days post-manure application (with 97 to 99% lower losses than broadcast, respectively). Dissolved reactive P and ammonium-N concentrations for both CT and VT were significantly lower three weeks after manure application compared to broadcast. Results suggest that VT reduced soil/residue disturbance while incorporating manure sufficiently to reduce sediment, N, and P transport potential under simulated high overland flow conditions.

Prediction of rill sediment transport capacity under different subsurface hydrologic conditions

When estimating rill sediment transport capacity for overland flow conditions, almost all widely used models focus on the impacts of surface hydraulic conditions and particle characteristics. However, the subsurface hydrologic impacts on the soil erosion process cannot be ignored. The upward force by exfiltration and the downward force by infiltration give opposite direction forces on the particles, which further influence sediment transport under seepage and drainage conditions. The aim of this research was to investigate the quantitative impacts of subsurface hydrologic conditions on sediment transport capacity in rills and improve the estimation of one existing transport capacity model by considering subsurface hydrologic effects. In this study, 216 rill flow experiments were completed in a 3.0 m long flume which contained four rill channels with slope lengths of 0.5, 1.0, 2.0, and 3.0 m. The experiments were conducted on close to uniform sands with four water discharge rates on 4.56%, 8.75%, and 12.17% slopes under four subsurface hydrologic conditions. The sediment transport rates from 192 of the 216 runs were estimated to have reached the sediment transport capacities for the corresponding condition based on the changes of sediment transport rates along the slope length and the surface elevation changes of the bottom region in the rills. The results indicated that rill sediment transport capacity increased significantly from free drainage to saturation conditions, and these differences increased with greater water discharge rates and greater slope gradients. Small increases in rill sediment transport capacity were observed from saturation to the 10 cm seepage condition with relatively stable differences. The selected sediment transport capacity equation provided good predictions under saturation and seepage conditions. The adjustment of water discharge rates improved the sediment transport capacity predictions with the discrepancy ratio between predictions and observations (P.O0.5–2.0) increasing from 73.0 to 90.5% under the free drainage condition and reaching 100% under the saturation and seepage conditions.

Effect of Napier grass shoots characteristics on runoff and sediment outflow under concentrated overland flow conditions

Vegetation cover is very effective measure to control environmental conditions. In this study, the potential of Napier grass to reduce soil erosion was evaluated. Parameters include number of stems, shoot length, number of leaves, leaf area index and experiments were performed using a hydraulic tilting flume and controlled water circulation system. Extensive experiments were carried out using (i) control (ii) whole plant plot and (iii) roots plot at 2% slope with 10.7 l/s/m discharge rate. Results summarized that Napier grass produced significantly lesser soil erosion and runoff as compared to the control. Further, it was observed that the sediment outflow and runoff generation significantly decreased with the growth stage of Napier grass. Roots were found more effective in controlling sediment rates, while shoots were more effective in reducing runoff rate. The correlation analysis indicated that runoff and sediment outflow was highly negatively correlated with the leaf area index and the number of stems, respectively.

Urban and overland flow modeling with dynamic adaptive mesh and implicit diffusive wave equation solver

A riverine and overland flow model based on the dynamically adapting Galerkin Least-Squares finite element method is developed and presented. The method utilizes the diffusive wave equations within a dynamically adaptive mesh and second-order accurate implicit time stepping scheme to efficiently and accurately simulate problems involving flows such as those that occur during overland flooding and urban inundation. The developed method and the utility of dynamic mesh adaption is presented through the simulation of common problems that occur in urban and overland flow conditions, these are shallow flooding, rapid flooding and flow propagation in an urban area. The application of the method to the flooding of the Morganza floodway illustrates the capabilities of the model in simulating large scale flooding and the application to a large dam break illustrates the limitations of the diffusive wave equations and the flow regimes where the numerical assumptions for the method break down. To the author's knowledge, the unique combination of FEM, wet-dry scheme and dynamic mesh adaption for the solution of diffusive wave equation (DWE) has not been presented in literature prior to this study.

Estimation of Soil Erosion to Define the Slope Length of Newly Reconstructed Gentle-Slope Lands in Hilly Mountainous Regions

Farming plot construction engineering in hilly areas plays an important role in the mechanization, large-scale production and industrialization of agriculture. The method is undertaken to improve water and soil conservation, enhance soil fertility and extend machinery agriculture. However, the positive effects of engineering require years to mature. The properties of newly reconstructed soil are not sufficient, i.e., with poor structure and low water holding capacity, resulting in deterioration of its physical properties and erosion. To date, most studies on plot characteristics and soil properties in farming plot construction engineering have neglected the influence of soil erosion. This paper addresses soil erosion characteristics at sites to define the appropriate slope length for newly reconstructed gentle-slope lands. Six field plots with a 10° slope gradient and different lengths (5, 10, 20, 30, 40, and 50 m) were established under natural rainfall and simulated overland flow conditions. The soil detachment rate, runoff shear stress and stream power exhibited the same trends as runoff and soil loss. The soil erosion characteristics varied at sites with different slope lengths, and the degree of soil erosion reached its minimum on gentle-slope land sites of 30 or 40 m. Therefore, 30–40 m slope lengths may be the recommended range to control soil loss from newly reconstructed gentle-slope lands. The conclusions of this study provide theoretical guidance for farming plot construction engineering, which can promote the sustainable development of cultivated land resources in hilly mountainous regions.

Typhoon Haiyan overwash sediments from Leyte Gulf coastlines show local spatial variations with hybrid storm and tsunami signatures

Marine inundation associated with the 5 to 8m storm surge of Typhoon Haiyan in 2013 left overwash sediments inland on the coastal plains of the northwestern shores of Leyte Gulf, Philippines. The Haiyan overwash deposit provides a modern sedimentary record of storm surge deposition from a Category 5 landfalling typhoon. We studied overwash sediments at two locations that experienced similar storm surge conditions but represent contrasting sedimentological regimes, namely a siliciclastic coast and a mixed siliciclastic-carbonate coast. The contrasting local geology is significantly reflected in the differences in sediment grain size, composition and sorting at the two sites. The Haiyan overwash sediments are predominantly sand and silt and can be traced up to ~1.6km inland, extending farther beyond the previously reported <300m inland limit of sedimentation. Sites with similar geology, topographic relief, and overland flow conditions show significant spatial variability of sediment thickness and inland extent. We infer that other local factors such as small-scale variations in topography and the type of vegetation cover might influence the spatial distribution of overwash sediments. The Haiyan overwash deposits exhibit planar stratification, a coarsening upward sequence, a non-systematic landward fining trend, and a sharp depositional (rarely erosional) basal contact with the underlying substrate. Overall, the Haiyan deposits have sedimentologic and stratigraphic characteristics that show a hybrid signature common to both storm and tsunami deposits.

Effects of Vegetation Stems on Hydraulics of Overland Flow Under Varying Water Discharges

AbstractVegetation plays an important role in soil erosion control, but few studies have been performed to quantify the effects of vegetation stems on hydraulics of overland flow. Laboratory flume experiments were conducted to investigate the potential effects of vegetation stems on Reynolds number, Froude number, flow velocity and hydraulic resistance of silt‐laden overland flow. Cylinders with diameter D of 2·0, 3·2 and 4·0 × 10−2 m were glued onto the flume bed to simulate the vegetation stems, and a bare slope was used as control. The flow discharge varied from 0·5 to 1·5 × 10−3 m3 s−1 and slope gradient was 9°. Results showed that Reynolds number on vegetated slope was significantly higher than that on bare slope because of the effect of vegetation stems on effective flow width. All the flows were supercritical flow, but Froude number decreased as D increased, implying a decrease in runoff ability to carry sediment. The mean flow velocity also decreased with D, while the velocity profile became steeper, and no significant differences were found in surface flow velocities among longitudinal sections on all slopes. Darcy–Weisbach friction coefficient increased with D, implying that the energy consumption of overland flow on hydraulic resistance increased. Reynolds number was not a unique predictor of hydraulic roughness on vegetated slopes. The total resistance on vegetated slopes was partitioned into grain resistance and vegetation resistance, and vegetation resistance accounted for almost 80% of the total resistance and was the dominant roughness element. Further studies are needed to extend and apply the insights obtained under controlled conditions to actual overland flow conditions. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Availability and performance of sediment detachment and transport functions for overland flow conditions

Soil erosion is a global environmental problem. To quantify water erosion rates at the field, hillslope or catchment scale, several spatially-distributed soil erosion models have been developed. The accuracy of those models depends largely on the sediment detachment and transport functions used, many of which were developed from empirical research. In this paper, the physical basis of the available sediment detachment and transport functions is reviewed, and their application boundaries determined. Well-known and widely-used sediment detachment and transport functions are discussed on the basis of composite force predictors, i.e. shear stress, stream power, unit stream power and effective stream power, and their suitability is elucidated based on information in the literature. It was found that only a few sediment detachment functions are available, and those have been poorly tested. Most erosion models ignore direct calculation of sediment detachment, but use the sediment transport capacity deficit approach to estimate detachment rate. Many more sediment transport functions are available that also tested better for overland flow conditions. However, our tests did not result in a single function that appeared to perform best under a range of experimental conditions. The unit stream power-based functions developed by Govers seem to be the most promising ones for water erosion modelling. It is therefore recommended to evaluate the performance of existing sediment transport functions with more detailed field and laboratory datasets.Editor Z.W. Kundzewicz

Experimental validation of a 2D overland flow model using high resolution water depth and velocity data

• A 2D overland flow model is validated using high resolution depth and velocity data. • Manning and Keulegan formulations produce similar and satisfactory results. • More complex formulations do not improve model performance. • The friction coefficient can be related to the micro and macro-rugosity of the bed. • The model might be used as the hydraulic base of a distributed soil erosion model. This paper presents a validation of a two-dimensional overland flow model using empirical laboratory data. Unlike previous publications in which model performance is evaluated as the ability to predict an outlet hydrograph, we use high resolution 2D water depth and velocity data to analyze to what degree the model is able to reproduce the spatial distribution of these variables. Several overland flow conditions over two impervious surfaces of the order of one square meter with different micro and macro-roughness characteristics are studied. The first surface is a simplified representation of a sinusoidal terrain with three crests and furrows, while the second one is a mould of a real agricultural seedbed terrain. We analyze four different bed friction parameterizations and we show that the performance of formulations which consider the transition between laminar, smooth turbulent and rough turbulent flow do not improve the results obtained with Manning or Keulegan formulas for rough turbulent flow. The simulations performed show that using Keulegan formula with a physically-based definition of the bed roughness coefficient, a two-dimensional shallow water model is able to reproduce satisfactorily the flow hydrodynamics. It is shown that, even if the resolution of the topography data and numerical mesh are high enough to include all the small scale features of the bed surface, the roughness coefficient must account for the macro-roughness characteristics of the terrain in order to correctly reproduce the flow hydrodynamics.

Experimental study of the water depth and rainfall intensity effects on the bed roughness coefficient used in distributed urban drainage models

Summary The work presented in this paper analyses the effect of water depth and rainfall intensity on the surface roughness coefficients used in overland flow models based on the shallow water equations. The relation between the Manning coefficient and the water depth and rainfall intensity has been quantified using different methodologies based on the analysis of two sets of experimental data. In the first set uniform overland flow conditions were generated, and the bed roughness coefficient was computed from direct measurements of the water depth and discharge. In the second set of experiments, unsteady rainfall–runoff transformations with different rainfall intensities were generated in a flume and computed with a shallow water model in which different bed friction formulations were implemented and calibrated. Results show that for very low water depth values there is a significant increase in the surface resistance, which is not captured by any standard bed friction formulation. Rainfall intensity also increases surface resistance especially as the water depth diminishes below a critical threshold. Using a Reynolds dependent formulation for the Manning coefficient improves model predictions.

A unit stream power based sediment transport function for overland flow

Soil erosion is a serious global problem requiring effective modeling for accurate assessment of sensitive areas and related erosion rates. The outcome of soil erosion models depends strongly on the estimation of sediment transport capacity. In most of the existing spatially distributed soil erosion models sediment transport capacity of overland flow is often estimated using stream flow transport capacity functions. The applicability of stream flow functions to overland flow conditions is questionable because hydraulic conditions like flow depth, slope steepness and surface roughness under overland flow are substantially different from stream flow conditions. Hence, the main objectives of this study were i) to check the suitability of five existing well known and widely used transport capacity functions (Yalin 1963; Low, 1989; Govers, 1990; modified Engelund and Hansen (Smith et al., 1995); and Abrahams et al., 2001) for use under overland flow conditions, and ii) to derive a new function based on unit stream power by dimensional analysis to quantify transport capacity for overland flow. To accomplish the objectives, experiments in a 3.0 m long and 0.5 m wide flume were carried out using four different sands (0.230, 0.536, 0.719, and 1.022 mm). The unit discharges used for experimentation ranged from 0.07 to 2.07 x 10(-3) m(2) s(-1) and slopes ranged from 5.2 to 17.6%. In this study, none of the predictions with the existing functions was in good agreement with measured results over the whole range of experimental conditions, especially at low flow intensities. The percentages of observations in which the discrepancy ratio ranged between 0.5 and 2.0 were: 65% (Yalin 1963), 74% (Low, 1989), 57% (Govers, 1990), 54% (modified Engelund and Hansen (Smith et al., 1995)), and 25% (Abrahams et al., 2001). The results showed that the selected functions reasonably estimate transport capacities only under those ranges of conditions for which they were formulated. Although the excess.shear stress concept based function (i.e. Low's function) produced excellent results, the degree of accuracy of the results varied substantially with grain size (P.O.(0.5-2.0): 53-100%). In contrast, the performance of the Govers' function, which is based on the unit stream power concept, was quite similar for all the selected sands (P.O.(0.5-2.0): 50-63%). Based on the unit stream power concept, a new function for low flow intensities was derived by dimensional analysis using the data gained from the flume experiments. (c) 2012 Elsevier B.V. All rights reserved.

Investigating the fate of sodium monofluoroacetate during rain events using modelling and field studies

We examined catchment-scale transport of sodium monofluoroacetate (‘1080’) in rainfall run-off. We developed a hydrological model describing the overland transport of 1080 and validated model results using field data from a headwater catchment, where we intensively sampled a stream during a rainfall event (28 mm in 8 h) that followed 1080 aerial application. Only one stream sample contained a measurable concentration of 1080 (0.1 µg/l; collected 105 min from the start of rainfall), while 1080 was below detection limits (0.1 µg/l) in all other samples. Absence of visually observable overland flow conditions (puddles and saturated areas connected to the stream) early during the rainfall event suggested that overland transport might not have been the dominant mechanism in this catchment. Moreover, analyses of soilwater samples collected from lysimeters installed in the catchment indicated the propensity of 1080 to leach into soil, suggesting the need to investigate subsurface transport pathways.

Effects of sediment load on hydraulics of overland flow on steep slopes

AbstractEroded sediment may have significant effects on the hydraulics of overland flow, but few studies have been performed to quantify these effects on steep slopes. This study investigated the potential effects of sediment load on Reynolds number, Froude number, flow depth, mean velocity, Darcy–Weisbach friction coefficient, shear stress, stream power, and unit stream power of overland flow in a sand‐glued hydraulic flume under a wide range of hydraulic conditions and sediment loads. Slope gradients were varied from 8·7 to 34·2%, unit flow rates from 0·66 to 5·26×10−3 m2 s−1, and sediment loads from 0 to 6·95 kg m−1 s−1. Both Reynolds number (Re) and Froude number (Fr) decreased as sediment load increased, implying a decrease in flow turbulence. This inverse relationship should be considered in modeling soil erosion processes. Flow depth increased as sediment load increased with a mean value of 1·227 mm, caused by an increase in volume of sediment‐laden flow (contribution 62·4%) and a decrease in mean flow velocity (contribution 37·6%). The mean flow velocity decreased by up to 0·071 m s−1 as sediment load increased. The Darcy–Weisbach friction coefficient (f) increased with sediment load, showing that the total energy consumption increased with sediment load. The effects of sediment load on f depended on flow discharge: as flow discharge increased, the influence of sediment load on f decreased due to increased flow depth and reduced relative roughness. Flow shear stress and stream power increased with sediment load, on average, by 80·5% and 60·2%, respectively; however, unit stream power decreased by an average of 11·1% as sediment load increased. Further studies are needed to extend and apply the insights obtained under these controlled conditions to real‐world overland flow conditions. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Investigation of Boundary Shear Stress and Pollutant Detachment from Impervious Surface during Simulated Urban Storm Runoff

Pollutant detachment rates have been determined for four chloride salts during simulated urban storm runoff. Under rainfall and/or overland flow conditions, chloride mass flux was measured and related to boundary shear stress of the test surface. Washoff coefficients, presumed to depend only on pollutant characteristics, were computed based on the slopes of dimensionless mass flux versus dimensionless time plots. Washoff coefficients were found to vary among and between the chloride compounds studied. In general, higher overland flow rates produced lower boundary shear and lower washoff coefficients. The combination of simulated rainfall and overland flow resulted in an increased boundary shear and an increased washoff coefficient. An empirical washoff coefficient based on a load characteristic curve derived from an exponential washoff relationship was also computed from the runoff data and compared with the previous washoff coefficient. A linear correlation between these two washoff coefficients was observed. The magnitude of the latter coefficient under simulated rainfall was consistent with reported values obtained from field data.

Modeling Event-Based Temporal Variability of Flow Resistance Coefficient

During the storm duration, the effects of surface resistance on the developing and receding overland flow depths (hj) on different flow parameters like the overland flow resistance coefficient (Nj), flow velocities (vj), Reynolds number (Rj), and Froude number (Fj) have been studied for the six natural catchments (0.012–92.5 km2) located in different agroclimatic regions of India. The kinematic wave (KW) equations are used for simulation of overland and channel flows using explicit methods for developing numerical solutions for the estimation of flow parameters at short durations. For the complete storm duration hj-Nj relationships have been found to form hysteresis loops. To predict resistance coefficients, simple hj-Nj relationships have been worked out separately for the rising and depleting overland flow conditions. Computed hydrographs simulated by incorporating these equations in the KW model agree well with the observed ones. The overall applicability of the suggested approach is successfully demon...

Evaluating a single‐class net deposition equation in overland flow conditions

The quantitative description of sediment transport across areas of net deposition is an essential part of assessing the off‐site effects of soil erosion on hillslopes. A new approach to describing sediment deposition across areas of net deposition, the single‐class Hairsine and Rose [1992a, 1992b] sediment deposition equation, is evaluated here using a series of controlled laboratory experiments. Hydraulic and sediment transport input parameters, sensitivity analysis, calibration using half the experimental data, and evaluation using the remaining data are presented. Simulations of overland flow hydraulics are evaluated using measured flow velocities. This evaluation shows that the Manning's equation gives a good estimate of flow velocities. Calibration is conducted by adjusting the fraction of stream power available for sediment (re)entrainment (F), and the threshold stream power below which no reentrainment occurs (Ωcr), to minimize the error between the simulated and the measured outflow sediment concentrations. The calibration runs show that the single‐class Hairsine et al. equation is very sensitive to the characteristic settling velocity adopted. The evaluation found that good simulations are obtained if appropriate threshold values are used. Incorporation of the reentrainment term significantly improves sediment outflow simulations above the threshold value.