| This study focused on using a two-dimensional (2-D) flow model to predict the velocity distribution and water depth in the sharp bend of a compound channel. The 2-D model was calibrated using flow measurements obtained over a range of discharges. Computed results from the model were used to predict pier scour depths using the SRICOS-EFA method (Briaud et al., 1999). The site examined is the Highway 13 Bridge over the Big Sioux River at Flandreau, South Dakota.;Before a 2-D hydraulic model of the Big Sioux River near Flandreau, SD was created, four general channels were created for the purpose of developing the proper methods of creating a 2-D model and compare the results of a 1-D model, HEC-RAS, and 2-D model, FESWMS, as the complexity of the channel's geometry was increased.;A topographical survey of the study site was conducted by the USGS that included elevation points along predetermined transects, pier locations, and abutment locations. As the 2-D model of the Big Sioux River near Flandreau, SD was developed, a procedure was written so the results could be reproduced. Once the 2-D model of the Flandreau site was developed, a sensitivity analysis was performed for each input parameter in FESMWS, the 2-D model chosen for this study. The Flandreau site has complex channel and floodplain geometries that produce unique hydraulic conditions at the bridge crossing. The hydraulic and geomorphic factors that affect the main channel and floodplain flows and the flow interactions between the two portions were examined. A 1-D model of the Flandreau site was created in conjunction with the 2-D model and the results were compared.;Overall, this research project provided insight into the capabilities of a 2-D model. The results of the 2-D model were used to correctly predict the measured scour depths at the Highway 13 Bridge crossing. This project also outlined the procedure for creating a 2-D model, examined the sensitivity of the model outputs to the input parameters, and developed a general understanding of 2-D flow effects at a river crossing in the bend of a compound channel. |
