Application of Frame Modeling To Evaluate Long-Term Morphological Changes In The Sabougla Creek Watershed

Previous studies of the Sabougla Creek Watershed, located in the north-central region of Mississippi, observed severe channel incision, bank erosion, and gully advancement in the upper portion of the basin caused by channel straightening in the early 1900s. These upstream erosion processes were also found to be contributing to excess sedimentation in the lower portion of the watershed. The Future River Analysis & Management Evaluation (FRAME) model, a new tool enabling long-term river morphology modeling over decadal and centennial scales, was used to simulate long-term changes in river shape and composition in the Sabougla Creek Watershed and investigate the impacts of potential channel modifications and various climate change scenarios. The FRAME tool is being developed by an international research consortium led by researchers at the USACE’s Engineer Research and Development Center (ERDC) in Vicksburg, Mississippi. FRAME is a hybrid model integrating 1-D hydraulic and sediment transport modeling techniques with empirical methods for channel form adjustments (see related presentation by Soar et al.). In coordination with the development of the FRAME tool, research is being conducted to translate sediment transport imbalances into morphological responses (see related presentation by Thorne et al.) and to develop user-friendly graphical interfaces and metrics that can facilitate management decision making (see related presentation by Downs et al.).

This study includes a 16-mile section of the Sabougla Creek and a 4-mile section of the upstream tributary of Bellefontaine Creek. Initially, a baseline scenario was developed assuming no channel modifications or changes in historical flow-duration patterns. The FRAME model was then used to evaluate the impacts of erosion control measures and potential climate change scenarios. These types of channel modifications and changes in hydrologic patterns can provide a range of complex and sometimes unexpected responses, which makes this site a good candidate for applying the FRAME tool. Prior to this study, the FRAME tool had been applied to a 70-mile reach of the Lower Mississippi River as an initial testbed study (see related presentation by Biedenharn et al.). Analysis of the Sabougla Creek required developing additional functionality within the FRAME tool including tributaries (flow change points), variable input bed material gradations, and multiple sediment transport equation options. For each of the different modeling scenarios, time series of simulation results for changes in cross-sectional area and bed material composition were compared to the baseline condition.