ARS | Publication request: SEDIMENT TRANSPORT CAPACITY AND EROSION PROCESS INTERNACTION

Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 23, 1999
Publication Date: N/A

Technical Abstract: Sediment transport capacity, Tc, is defined as the maximum amount of sediment that a flow can transport. The difference between Tc and sediment load, Qs, is used to calculate detachment or deposition rate in the current USDA process-based erosion prediction model, i.e., WEPP. Under this model concept, detachment occurs when Tc > Qs and deposition occurs when Qs > Tc. Despite its extensive usage in modeling erosion processes, the value of Tc was rarely measured, especially from an erodible surface. The objective of this work was to quantify sediment transport processes from shallow surface flows in a rill channel. A multiple box system, consisting of a cascade of three soil boxes, is designed to simulate sediment transport processes in a segment of the hillslope. For this study, the two upslope boxes were used as the sediment sorce and the third box was partitioned to three 0.2-m wide replicate rill channels. The flow rate, flow velocity and sediment delivery in the rill channel were investigated under different soil hydrologic conditions, slopes, rainfall intensities and sediment feeding rates. Data showed the importance of raindrop impact as well as slope steepness and hydrologic conditions on sediment delivery and the dominant erosion process. Even under a deposition dominated regime, the sediment delivery increases as the sediment feeding rate is increased. The data set suggests a non-unique sediment transport capacity that is dependent on the dynamic equilibrium of erosion, deposition and transport processes. A conceptual framework which accounts for simultaneous erosion and deposition processes has been proposed and a preliminary analyses of the analytic model with the experimental data will be demonstrated.