EVALUATING MODEL ACCURACY: PREDICTED AND OBSERVED SEDIMENT DEPOSITION DOWNSTREAM OF THE CHILOQUIN DAM REMOVAL

Hydrodynamic models are often used to reduce uncertainty regarding the outcomes of dam removal, though the accuracy of these models is not regularly evaluated post-removal. With the goal of improving our understanding on the accuracy and limitations of making predictions of sediment dynamics following dam removal, we compare predicted and observed sediment deposition at three sites downstream of the Chiloquin Dam removal. Results from a 1D hydraulic model, developed to estimate sediment transport rates at the sites, are compared to cross-sectional and longitudinal profile surveys collected approximately one year following the dam removal. Pre-removal and post-removal bathymetry and grain size distributions document the changes in depth, size, and mass of sand downstream. Model predictions provided estimates of mass of sediment remaining and the thickness of sediment in the channel following removal. The relationships between the model predictions and observations are reported and potential sources of error and improvement in modeling and field observations are discussed.