Some applications of flood routing methods with particular reference to small streams
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An analysis of a large number of flood routing methods has been carried out, and the implicit solution of the full unsteady flow equations selected as the most appropriate technique for complex flood routing problems. Simpler flood routing methods, recommended in the N.E.R.C. Flood Studies Report, are compared with techniques based on the integration of the full unsteady flow equations. A versatile implicit method computer program has been developed. Its applicability to varied open channel phenomena, including tidal and non-tidal flow, and surge wave propagation, is demonstrated. A variable finite difference weighting factor is recommended, and a strategy outlined for the optimisation of stability and accuracy of computation. The implicit solution of the one-dimensional unsteady flow equations is utilised in the development of a flood routing model of the Rive Mole, Surrey. Results indicate that the treatment of flood plains as storage areas only may produce large errors in the synthesis of large design floods. The Flood Studies Report method of flood hydrograph generation is used to produce an overall river/catchment model, but the suitability of the F.S.R. Method to the whole River Mole catchment is questioned. Finally, the benefits of using a computational model for flood forecasting and design are evaluated in comparison with techniques currently in use, and a general strategy is formulated for the analysis of flood routing problems in small streams.