Pa Vinh Tailwater Scour (Vietnam)

DSI conducted a study to determine the potential for tailwater scour downstream of the proposed Son La Reservoir (Pa Vinh Dam), Vietnam. One of the uses of the study was to help set the turbine elevations.

A two dimensional (2D vertically averaged) hydrodynamic and sediment transport model was developed. The numerical code used was the EFDC_DS model. This model is part of the EFDC/EFDC_Explorer Modeling system for 2D/3D hydrodynamic, sediment, toxics and water quality. One monsoon season was used for the model verification effort.

Once validated, the EFDC model was used to predict scour and deposition patterns for the main channel and floodplains downstream of the dam. The Hoa Binh Reservoir is located about 15 km below the Pa Vinh Dam. It was determined that there would be significant scour regions and deposition areas. Fortunately, however, the erosion would be significantly reduced due to a naturally armored reach of the river about 2.5 km below the dam. Recommendations for further study and longer simulation times were made.