Sediment Transport Capacity of Sheet and Rill Flow: Application of Unit Stream Power Theory

Abstract

Theoretical equations for calculating the unit stream power of both sheet and rill flow were developed and used to predict the sediment transport capacity of such flows. Independent data sets from three sources representing both finely aggregated clay soils and coarse textured nonaggregated soils, sheet, rill, and composite sheet rill flow systems, and a range of slopes were used to test the utility of the method. The results were very good and demonstrated the simplicity and robustness of the method. For shallow overland flow the best results were obtained when the critical unit stream power at incipient sediment motion was treated as a constant value that was independent of slope. The results also suggest that a unique value of critical unit stream power for rill initiation exists that is independent of soil type. For noncohesive loams or fine sands and finely aggregated clay soils the sediment transport capacity can be accurately predicted from a knowledge of the physical characteristics of the soil or bed material alone. For aggregated clay soils this requires information on the aggregate size distribution and the effects of soil particle size differentiation as flow rates and unit stream powers increase with the transition from sheet to rill flow.

Effect of hydraulic parameters on sediment transport capacity in overland flow over erodible beds

“…The non-significant effect of grain size on the relationship between transport capacity and unit stream power was somewhat surprising, because grain size has been seen to have considerable effect on mean flow velocity (Ali et al, 2012). These results do agree with the findings of previous researchers (Govers and Rauws, 1986;Moore and Burch, 1986;Govers, 1990) in such a way that the unit stream power theory showed greatest potential for estimating transport capacity of overland flow under erodible beds. But they contradict earlier findings in the sense that the exponent of unit stream power was independent of grain size.…”

“…Accordingly, different composite force predictors were used to estimate transport capacity of overland flow, i.e. shear stress, stream power, unit stream power, and effective stream power (Yang, 1972;Moore and Burch, 1986;Govers and Rauws, 1986;Lu et al, 1989;Govers, 1990Govers, , 1992Everaert, 1991;Jayawardena and Bhuiyan, 1999;Prosser and Rustomji, 2000;Abrahams et al, 2001;Zhang et al, 2009). But widely varying results were obtained because the performance of composite force predictors were tested under different ranges of morphologic conditions.…”

An artificial neural network application to produce debris source areas of Barla, Besparmak, and Kapi Mountains (NW Taurids, Turkey)

“…Descriptive statistical evaluations suggest that particularly the mean values of SPI for debris source areas (1.42) and for areas free from debris (0.93), the importance of the index SPI in generation of debris material is comprehensible. The other secondary topographical attribute used in this study is the sediment transport capacity index (LS) (Moore and Burch, 1986). The calculation of LS value is given in the equation below:…”

Modelling soil bulk density at the landscape scale and its contributions to C stock uncertainty

“…The SWI is based on the ratio of contributing upslope area per unit contour width and local slope angle (Böhner et al, 2001). The STI is based on unit stream power theory, where upslope contributing area is directly related to discharge (Moore and Burch, 1986). Classification algorithms were used to divide the landscape into 7 and 8 homogeneous topographic classes on the basis of curvature, slope and catchment size (Pennock et al, 1987), and slope, surface texture and local convexity respectively (Iwahashi and Pike, 2007).…”