Evaluating Impacts of Porous Check Dams on Flow Routing and Sediment Transport in Agricultural Ditches: A Case Study in the Mississippi Delta, Bulletin 1213

Diaz-Ramirez, J., McAnally, W. H., Kroger, R., & Martin, James L. (2014). Evaluating Impacts of Porous Check Dams on Flow Routing and Sediment Transport in Agricultural Ditches: A Case Study in the Mississippi Delta, Bulletin 1213. Mississippi State University: Mississippi Agricultural and Forestry Experiment Station. (1213).

Management and reduction of sediments and nutrients reaching water bodies are priorities of several local, state, and federal agencies in the U.S. The main goal of this research was to evaluate hydraulic characteristics and sediment-trapping efficiency of three porous check dams constructed in the main ditch of an agricultural field in Coahoma County, Mississippi. The methods used in this study included field data (land cover, soil characteristics, area size, rainfall, evapotranspiration, cross-section surveys, water levels, and suspended sediment concentrations), geographical information systems (ArcGIS, aerial photos, Google Earth), and modeling tools (USEPA BASINS suite of programs). This approach yielded a Hydrological Simulation Program – FORTRAN (HSPF) processes-based model of rainfall-runoff, soil erosion, hydraulics, and sediment transport of the study area. The model simulated values of observed water-depth values for low and mean conditions well. The model could not adequately represent conditions of high flows due to hydraulic restrictions of the flow (culverts and downstream ponding) that were not input into the HSPF hydraulic processes. After model calibration and verification of water depths were completed, the HSPF model computed 15-minute continuous streamflow, total suspended sediments, rate of change of bed sediments, and sediment loads through the main ditch. Simulated streamflow and total suspended sediments were not evaluated due to lack of observed flow data and short suspended sediment time series. This study assumed that sediment particle distribution in storm runoff was dominated by fine sediments (silt 70% and clay 20%). Considering model uncertainties (e.g., lumped channel discretization, lack of understanding of flow-stage relationships in porous check dams) along with incomplete field data (e.g., two suspended sediment samples during the rising limb of storm hydrographs), the model predicted a moderate sediment trapping efficiency (35%) in the main ditch. Design guidelines of porous check dams suggest low retention values of fine sediments. This study is useful in providing information to improve field-data collection efforts. In addition, this research presents a framework to evaluate sediment control structures like porous check dams in the Mississippi Delta region using the USEPA BASINS/HSPF model.