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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #357925

Research Project: Conservation Practice Impacts on Water Quality at Field and Watershed Scales

Location: National Soil Erosion Research Laboratory

Title: Inferring sediment transport capacity from soil microtopography changes on a laboratory hillslope

item NOUWAKPO, SAYJRO KOSSI - University Of Nevada
item Huang, Chi Hua
item BOWLING, LAURA - Purdue University
item OWENS, PHILLIP - Purdue University
item Weltz, Mark

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2021
Publication Date: 3/29/2021
Citation: Nouwakpo, S., Huang, C., Bowling, L., Owens, P., Weltz, M.A. 2021. Inferring sediment transport capacity from soil microtopography changes on a laboratory hillslope. Water. 13:929.

Interpretive Summary: In the development of process-based soil erosion models, the concept of sediment transport capacity (Tc) has been used as the maximum amount of sediment that a flow can carry. Nevertheless, the concept of Tc has not been experimentally tested and validated. In a laboratory experiment where the detailed surface topographic data were collected before and after rainfall events to allow the calculation of erosion (a decrease in surface elevation) and deposition (increase in elevation). We found that the flow hydraulics to initiate sediment deposition, i.e., the hypothetical situation when the flow has reached an apparently Tc, was much lower for the surface bed with water draining into the soil as compared to the situation when the soil bed with subsurface water seeping out into the surface. The findings could not be explained by the current Tc-based soil erosion models, indicating the need to revise or propose new soil erosion and sediment transport concepts that can properly describe the experimental results.

Technical Abstract: In hillslope erosion, the Transport Capacity (Tc) concept describes an upper limit to the flux of sediment transportable by a flow of given hydraulic characteristics. This widely used concept in process-based erosion modeling faces challenges due to scarcity of experimental data to strengthen its validity. In this paper, we propose a methodology to infer the exceedance of transport capacity by concentrated flow from changes to soil surface microtopography sustained during rainfall-runoff events. Digital Elevation Models (DEMs) corresponding to pre- and post- rainfall events were used to compute elevation change maps and estimate spatially-varying flow hydraulics ' taken as the product of flow accumulation and local slope. These spatial data were used to calculate a probability of erosion PE, at regular flow hydraulics intervals. The exceedance of Tc was inferred from the crossing of the PE = 0.5 line. Sustained net deposition occurred under drainage condition at flow hydraulics 1.5 times lower than that required to initiate deposition under seepage conditions. Results from this study suggest pulsating erosion patterns along concentrated flow networks with intermittent increases in PE to local maxima followed by declines to local minima. These short-range erosion patterns could not be explained by current Tc-based erosion models. Nevertheless, Tc-based erosion models adequately capture observed decline in local PE maxima as ' increased.