Numerical modelling of river flow— data collection and problem solving

The discrepancy between the theoretical solution of the Saint-Venant equations for flood routing calculations and the problems encountered during practical implementation is often quite big. This paper tries to give an overview of the different bottle necks and the possibilities to cover the gap between theory and practice. After a brief overview of the equations used for steady and unsteady flow simulation, collection of topographical and hydraulic data is discussed. Then follows some practical considerations on the processing of input data on cross-sections, longitudinal profile and friction coefficient. Finally the impact of different approaches on the quality of the numerical simulation is illustrated by some practical examples.