Predicting Stage-Discharge Curves in Channels with Bank Vegetation

Many flood-control channels are subjected to expensive and environmentally damaging maintenance practices to control vegetation growth in attempts to preserve flood capacity. However, such maintenance regimes are often based on vague and qualitative guidelines. There is a clear need for physically based methods of predicting the impacts of vegetation growth on flow resistance and flood capacity. In the present note, a numerical hydraulic model is coupled with physically based flow-resistance equations for gravel-bed materials and vegetation roughness elements. The resulting model is capable of simulating stage-discharge curves in channels with arbitrary cross-sectional geometry, gravel-bed materials and bank, and/or floodplain vegetation, including overbank flows. The new model is demonstrated to be capable of closely replicating the stage-discharge curve at a study site on a natural river channel. Finally, the model is demonstrated using examples in which the effects on flood capacity of seasonal vegetation growth are simulated at the study site.