The Impact of Flood Retarding Structures and Varying Climatic Conditions on Streamflow and Sediment Response for a Watershed in Southwestern Oklahoma

Flood retarding structures (FRSs) represent one of the most effective methods for reducing damages caused by flooding and sedimentation from agricultural land. The impacts of these structures on streamflow and sediment regime and their effectiveness in reducing watershed floods and associated soil losses under dry, average, and wet climatic conditions were investigated in this study. The Soil and Water Assessment Tool (SWAT) was used to determine differences in streamflow and sediment characteristics with and without flood retarding structures under varying climatic conditions on two subwatersheds of the Little Washita River Experimental Watershed (LWREW) in Southwestern Oklahoma. Differences in the reduction of sediment yield between the two subwatersheds were attributed to such factors as the combined sediment storage capacity of the impoundment structures, their distance from the watershed outlet, and the percent of watershed area controlled by the structures. Model simulations from this study confirm the importance of the flood abatement program in reducing flooding and soil losses from agricultural land, but also show that low flow conditions may be exacerbated by the FRSs.