Enhancing Urban Drainage Resilience: Integrated 1D/2D PCSWMM Modeling for Mitigate Flooding Risks in Residential Neighborhoods

This paper presents a feasibility-level flood assessment for the Riverside Park community in Ottawa, Canada, using an integrated 1D–2D PCSWMM modelling approach to evaluate existing drainage performance and identify effective mitigation strategies. Riverside Park experienced significant flooding during the 2023 storm event, which highlighted deficiencies in both the minor storm sewer system and the poorly defined major overland drainage network.

The model integrates a city wide1D storm sewer network model with a 2D overland domain representing streets, parks, rear yards, catchbasins, depressed driveways, and outfalls to receiving waters. Simulations covered standard design storms across typical return periods and a climate stress test, with a recent extreme event for validation.

The 2D framework reproduces observed flood pathways, including storm-sewer surcharge, surface ponding at low points, inflows to depressed driveways, and rear-yard conveyance through low-lying corridors. Screening of existing conditions indicates constraints in the minor system, persistent reliance of the major system on the minor system due to the absence of a defined overland outlet, and legacy grading not designed for dual drainage. Together, these factors concentrate runoff at bottlenecks and increase the likelihood of basement flooding and surface accumulation during intense storms.

Mitigation was assessed as coordinated public works and outlet enhancements. Public works include added storage in open spaces, selective sewer upsizing at critical links, inlet control devices to moderate capture and distribute flows, right-of-way regrading near vulnerable driveways, boulevard raising to interrupt unintended flow paths, a high-capacity relief conduit along a critical corridor. Outlet enhancements create redundancy at a rail crossing and establish a secondary overland and sewer outlet to the receiving system. Modelled scenarios show improved conveyance and flood tolerance in the minor system, reduced basement flooding, and targeted benefits to the major system, while recognizing that constraints at downstream outlets limit performance without broader system changes.

Overall, the 2D PCSWMM approach diagnoses coupled surface–sewer interactions, validates against observations, and prioritizes feasible, incremental measures. While no single intervention resolves risk under current constraints, the combined program offers defensible, staged improvements and a clear roadmap for next steps. This study highlights the value of integrated 2D PCSWMM modelling as a practical decision-support tool for urban flood mitigation planning in municipal environments.

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