Submitted to: International Symposium on Soil Erosion and Dryland Farming
Publication Type: Abstract Only
Publication Acceptance Date: 9/14/1998
Publication Date: N/A
Technical Abstract: Considerable effort to quantify sediment delivery has been conducted, but much less information is available on sediment size distributions and their relationships to soil condition and sediment regime during rainfall events. A dual-box system, consisting of a lower 5-m long study box and an upper 1.8-m sediment source box, was fabricated. These two boxes can be set at different slopes, seepage or drainage conditions and rained at different intensities. This setup allows us to simulate surface and subsurface hydrologic conditions of a 5-m slope segment anywhere on the hillslope. A preliminary study on the lower 5-m box with the Glynwood clay loam showed that the combination of a seepage condition and surface inflow caused severe rilling on the surface. When the surface is under drainage condition, erosion is limited to the interrill-type sheet erosion. For this clayey soil, the increased sediment deliveries from seepage condition were 2 to 10 times higher under rainfall alone and rainfall plus inflow as compared to those from drainage condition. These data demonstrated that seepage condition triggered the formation of rills and gullies in areas with impervious subsoil layer. Another experiment has begun to explore sediment detachment/transport relationship and size distributions in the dual-box system. With the upper 1.8-m box acting as the sediment feeder, this dual-box system allows us to quantify processes occurring at the lower 5-m control section by monitoring sediment coming in and going out of this section. Runoff samples were sieved during rainfall events. Sediment size data, along with total sediment delivery, will be used to study soil erosion processes at different surface conditions and hillslope positions.