Four different numerical models are developed to simulate the flow resulting from a breached dam. The models are a level-reservoir-approximation model, an explicit method-of-characteristics model, an implicit method-of-characteristics model and a linearized implicit finite-difference model. The first model is based upon the storage form of the continuity equation, and the other models are based upon the complete St. Venant equations. Laboratory experiments are performed to investigate the flow characteristics and to verify the validity of the numerical models. Comparisons between model results and experiment are used to evaluate the accuracy of the numerical models. These comparisons show that the explicit method-of-characteristics model always gives a more accurate solution than the other models. Computational problems, computer requirements and model robustness are also evaluated to assess ease-of-use of the models. Finally, the experimental and numerical results were used to construct a simplified numerical model to compute dam-break outflow hydrographs. The outflow hydrographs computed by this simplified model agree relatively closely with the corresponding results computed by the explicit method-of-characteristics model for any breach size. This suggests that the simplified model can be used for a wide range of breach sizes and gives a maximum practical level of accuracy.
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