On the interaction between stormwater drainage systems and rivers in urban areas: A case study located in Quebec City

As part of the rehabilitation program of its infrastructures, the Ministère des Transports du Québec (MTQ) will carry out the reconstruction of a section of a major highway located in Quebec City, Canada. WSP Canada inc. (WSP) has been mandated to establish the storm water drainage system redevelopment plan. WSP chose PCSWMM software to fulfill its mandate.

The special feature of this study is that the outfalls of the studied storm water networks (watershed area = 739 ha) are all located in a river known for its very reactive behavior. This river is also known to cause flooding problems in the city. One of the main objectives is therefore to ensure that total discharges in the river including those coming from the studied storm water system and following the rehabilitation of the highway are similar or lower in relation to current discharges. Thus, the model includes hydraulic section of that river (watershed area = 6696 ha) and reproduces its behavior. Simulations of known rain events corresponded well with field observations.  This allows analyzing and understanding the dynamic interaction that occurs between storm water outflows coming from the highway and the river. This is, in our opinion, a very interesting issue that more and more cities may have to address in the near future.

As part of this presentation, we will discuss the project and about the PCSWMM model. We will present how the model was constructed, calibrated and a part of the results obtained.