Development of 1D-2D dual drainage model for commercial and industrial lands in the southdown district of Mississauga, Ontario

The Southdown Grid LID project will assess the technical and financial feasibility of implementing communal, integrated water management systems on private property. This will involve aggregating properties together to share communal systems designed to achieve stormwater management and water conservation objectives, and to realize reductions in infiltration and inflow (i.e. stormwater ingress) to the sanitary sewer system.

A complete understanding of the existing hydrologic and hydraulic conditions allows the characterization of baseline conditions for the study area. To evaluate existing conditions scenario a PCSWMM model was developed to represent 37.4 ha (92 ac) of I/C lands, consisting of thirteen (13) separate property parcels in the Southdown project area.

This presentation will provide an overview of the approaches taken for the development of an integrated PCSWMM model to represent baseline conditions of the area with following components:

• 1D-2D hydrologic, hydraulic, and water quality model
• Surface runoff modeling considering different land uses
• Modeling 2D component to represent overland flooding
• Comparison of the peak flows, total runoff volumes, and pollutant loading (TSS & TP) for a range of design storm events as well as seasonal/annual precipitation patterns
• Identification and quantification of sanitary sewer inflows contributed by stormwater sources; the study area lies within an I/I priority location of concern
• Snowmelt component for continuous simulations
• Impact of climate change on existing sewer system

The overarching goal of existing conditions model development is to support the development of an approach which advances the wide scale adoption of distributed and decentralized stormwater management practices on private property through public/private partnerships.