Numerical Modelling of the Sediment Re-Suspension Induced by Boat Traffic

Fluvial transport in inland waterways is used in France and Europe since millennia. It was the most effective transport mode for goods and merchandizes before the development of the terrestrial alternatives. As an illustration, the French network of the inland waterways counted 12800 km of both, rivers and channels, at the beginning of the twentieth century. The huge development of highways and railways encountered in France has progressively decreased the use of fluvial transport. By considering the duration for the transport, the terrestrial mode looks more attractive than the fluvial one. But, the actual context of climate change and the international or European commitments to strongly diminish CO2 emissions are pleading for the reverse modal transfer, i.e. from highways and/or railways to waterways. Rebalancing the different transport modes are indeed compatible with the sustainable development concepts facing against road saturation, CO2 emissions, visual or noise pollutions while ensuring a better safety. Even through the shared awareness and the common efforts to increase the river traffic, this transport mode is still considered "under-developed" in the white paper of the European commission of 2001. For example, the fluvial transport in France has increased by 30% in ten years (1997− 2007), but it only represents 3% of the means of transport. And the recent recommendations in "Grenelle de l’environnement" initiated by the Frenchministry of ecology may accelerate the rebalance between rails, roads and rivers, carrying the ambition of a 25% report from the road down to the river by 2020. However, the development of this transport mode will certainly have economical and ecological consequences on the river management. The intensification of the river traffic by increasing the size and/or the frequency of passing boats will impact the actual management plan of the river. The waves induced by navigation could become stronger and bank erosion more frequent. The induced currents may be more intense and the resulting sediment transport more problematic. Indeed, it is accepted in aquatic environment that erosion Numerical Modelling of the Sediment Re-Suspension Induced by Boat Traffic 3