Flow control on a new residential sector in a natural area using a 2D-Double drainage model: A case study

A coupled 2D Double drainage PCSWMM model was built to study the storm water management and the design of an urban development at the City of Ile-Perrot, Quebec. The model's double drainage component deals with the traditional urban basins runoff whereas the 2D component fulfill the surface runoff simulation needs of the natural areas by reproducing the flow on the fields and the open water reservoirs. The hydrologic simulation of these areas was conducted by clustering different 2D contour sectors on subareas, based upon topographic characteristics, physical resolution requirements and hydrological parameters. Both model components are linked by simple simulation elements like conduits, weirs and outlets. The project foresees to integrate new residential sectors with the existing natural ponds and to be constructed basins that are designed and used for storm water retention, while offering supplementary leisure space for visitors. The controlled flow from these areas is limited to a total maximum flow at the downstream conduits. Environmental provincial regulations implying the removal of 80% of TSS were also considered to ensure the protection of the existing species in the ponds from the water runoff pollution. The so called ‘quality rainfall’ (a 25mm, 12 hours Chicago type synthetic rainfall) was used to address the environmental requirements about TSS’s, catching the runoff of the future residential areas by the use of a sedimentation basin. The coupled retention basin was then designed to manage the water volume produced by a 100 years return period synthetic rainfall. Simulation results satisfy both the regulations and the volume-flow limitations, allowing the project’s submission to the government agencies for approval and eventual construction.