By Jayson Adam, Eng., and Mélissa Breton-Dufour, Eng., M. Sc. A.
Episodes of intense rainfall are becoming more frequent, placing increasing pressure on urban infrastructure. In the context of climate change, stormwater management can no longer be treated as a simple technical issue addressed at the end of a project. It is becoming a central component of planning, directly linked to the durability, resilience, and overall performance of developments.
Stormwater retention aims to control the volumes and flow rates generated by precipitation in order to limit downstream impacts. The increase in impervious surfaces leads to higher peak flows, intensifying the risk of network overload, flooding, and degradation of receiving environments. Designing sustainable infrastructure therefore requires managing water at the source, considering not only current conditions but also increasingly intense future rainfall events.
Integrating Water Management from the Earliest Project Stages
A key success factor lies in involving infrastructure teams early in the project process. Too often, stormwater management is addressed late in the design phase, which limits technical options and increases costs.
Beginning at the conceptual stage, a comprehensive analysis helps identify the solutions best suited to the site:
- Topography and natural drainage patterns
- Soil characteristics and infiltration potential
- Land-use and urban constraints
- Local regulatory requirements
This proactive approach encourages integrated solutions that are optimized and aligned with the overall project.
High-Performance Infrastructure at the Core of Stormwater Management
Open-air retention basins are among the most effective and versatile solutions to address these challenges. Whether dry basins or permanent-pool basins, these facilities temporarily or permanently store excess runoff while limiting peak flows discharged into the municipal network or receiving water bodies. They are generally designed to manage rainfall events with return periods of up to 1-in-100 years, thereby providing enhanced protection against extreme weather events.
The hydraulic performance of these basins relies on the rigorous design of control structures, including calibrated orifices, safety spillways, valves, and bypass systems. These components enable precise flow regulation, ensure infrastructure safety during major storm events, and meet the requirements of municipal regulations and the MELCCFP, particularly with respect to simulated rainfall events, flow control, and flood protection.
Beyond flow control, open-air retention basins also play an important role in improving water quality. They help reduce suspended solids (TSS) before stormwater is discharged into receiving streams. This aspect is frequently required by the MELCCFP, as well as by several municipal regulations, within stormwater management projects, in addition to quantitative flow control requirements.
Retention basins also fit effectively within a comprehensive stormwater management strategy. When integrated with swales, ditches, green corridors, or infiltration structures, they help reduce the volumes directed to sewer networks and wastewater treatment plants while mitigating hydraulic surcharges. This integrated approach also improves the environmental performance of projects by promoting the settling of suspended solids and improving the quality of discharged water.
When well designed, open-air retention basins can also become valuable urban features. Thoughtful landscape design, combined with appropriate safety measures, allows for harmonious coexistence with surrounding communities and transforms a technical structure into a meaningful element of the urban landscape. Achieving this requires a multidisciplinary approach bringing together civil and hydraulic engineers, landscape architects, and urban planners to ensure coherent integration into the urban fabric.
Finally, the long-term sustainability of these facilities depends on a clear maintenance plan and proper support for municipalities. Designing with operational needs in mind from the outset helps maintain the hydraulic and environmental performance of retention basins over time.
Open-air retention basins therefore represent much more than a regulatory requirement. They are a strategic lever for designing resilient, sustainable infrastructure adapted to current and future climate realities.
