Study of the impacts of climate change on the water level rise of the Des Prairies river

This project studies the impacts of climate change on the water level rise of the Des-Prairies River (Montreal, Quebec, Canada), i.e. the expected increase in water surface elevation due to a future precipitation event. However, the aim is not to produce exact results about future level in the Des-Prairies River that could be used directly by the municipalities to make urbanization plans or to take adaptive measures. Indeed there are a lot of uncertainties involved in the different steps of such a process, and it was not possible with limited time, data and resources to provide so precise results. The main objective was rather to provide municipalities and public services managers involved in such a matter with a methodology to follow, different numerical methods that can be used, type of results that can be expected, and kind of uncertainties related to this approach. That is why a critical and comparative view on the different available methods and results has been adopted at each step, in order to give the more complete information, and to develop a full comprehensive approach of the effects of climate change on a river system, from the definition of climate change scenarios to the delimitation of an eventual flooding zone. So that the municipalities managers and experts would have information and tools in hands if they want to go forwards and sponsor a deep study to take eventual adaptive measures. The percentage of augmentation of precipitation intensity for 2041-2070 period taken form Mailhot et al (2007), applied to a 24h rainfall event of 50 years return period, permitted to determine the future precipitation data. The utilization of the Hec-GeoHMS software to make the rainfall-runoff transformation gave the future flow hydrograph, which was input into Hec-GeoRAS and River2D software – calibrated with known water elevations and flows. The results of the hydrodynamic simulations showed that some flooded zones were expected in the upper reach of the Des-Prairies River as well as near the outlet, but that the bridges would not get submerged or swept away. Finally, recommendations of use for 1D and 2D models were done according to the quality of the terrain data available, the complexity and the extent of the area under investigation, the flow regime, the existence of hydraulic structure and the type of results desired.