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Recent flooding events in North America have revealed deficiencies in existing stormwater infrastructure and management practices. The development of effective and efficient designs requires a comprehensive understanding of flooding in urban areas and complex open channel and overland flow systems. Traditional one dimensional (1D) models are used to simulate flow in river channels and gravity collection networks but are inadequate for simulating phenomenon such as significant street flooding and overbank flow in flood plains that occurs during extreme events. 1D/2D and 2D models have begun to be used but their complexity, cost and significant data requirements have limited their application. The availability of high quality digital terrain models (DTMs), the increased power of desktop computers as well as the need for more realistic simulation of flooding have all contributed to the adoption of 2D models for flood plain mapping and the analysis of overland flows. xpswmm is a comprehensive 1D hydraulics and hydrology modeling package for stormwater and wastewater systems. xpswmm2D was created by coupling the 1D capabilities of the xpswmm software package with the 2D hydrodynamic model TUFLOW. An additional feature was created to dynamically link 1D nodes and links to 2D cells in a single model.

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The application of the diffusion model to bed degradation due to the sudden cessation of sediment supply to an alluvial system has been investigated and limitations of the model noted. Experiments indicate that local maximum scour depths do not occur at the upstream end of an erodible reach. This was accounted for by modifying the diffusion model to include a mobile upstream boundary scheme. The modified model was calibrated using bed load sediment transport data and diffusion coefficient values of best fit obtained. Signifi cant differences between calibrated and predicted diffusion coefficient values were obtained. Measured and predicted bed profiles were also compared and conclusions about the applicability of the diffusion model to bed degradation drawn. RÉSUMÉCette étude traite de Papplication des modèles de diffusion a l'érosion d'un lit fluvial sous l'effet d'un blocage brutal de l'apport solide, avec la mise en evidence des limitations de ces modèles. Les recherches experimen tal montrent que les profondeurs maximales d'affouillement ne sont pas observées a L-extrêmité amont du bief affouillable. Cela a été pris en compte par une modification du modèle de diffusion consistant a prendre une limite amont mobile. Le modèle ainsi modifié a été étalonné a partir de résultats expérimentaux de charriage, ce qui a fourni, des valeurs de coefficient de diffusion a adopter. On a constate des differences significatives entre les valeurs prévues du coefficient de diffusion et celles resultant de l'étalonnage. On a également compare les profils en long du lit mesurés et calculés, ce qui a conduit a tirer des conclusions quant a l'applicabilité des modèles de diffusion a l'érosion des lits fluviaux.