Stormwater best management practices | Coping with climate change

What is it?

Season after season, rainwater, groundwater, lakes and snow are at the heart of natural life and living environments.

However, the challenge of water management is now greater than ever due to climate change and ever-increasing urbanization, affecting the capacity of public systems and infrastructures. These structures alone can no longer adequately control stormwater, leading to environmental impacts and flooding. Indeed, soil sealing and the loss of woodlands and other natural spaces modify the water cycle in urban areas, limiting the absorption capacity of soils and increasing runoff into storm sewer systems and even watercourses.

With networks saturated in many cases, backflow and flooding problems are frequent. Municipal authorities have no choice but to be aware of the challenges of sustainable stormwater management.

A municipality wishing to plan the development of its territory in a sustainable manner has every advantage in adopting a stormwater management plan. Stormwater Best Management Practices (BMPs) are among the most innovative practices developed in this field. They can be integrated into regulations (zoning, PIIA) for private development projects and public amenities, rather than simple retention basins designed according to an engineering approach.

The approach is essentially to encourage infiltration into the ground rather than runoff, to avoid, among other things, polluting the water table and excess water in storm sewers. This means treating the water at source and keeping it on site, and ensuring slower runoff through retention and filtration methods, or redirecting the water into planned absorption zones by reproducing the natural path of the water cycle.

BMP principles

Bioretention is the key to this approach. It uses the phytotechnological properties of plants and soils to filter, retain and infiltrate water into the soil. A number of structures are a form of bioretention at source, such as landscaped valleys, retention basins, rain gardens and vegetated ditches. These infrastructures can also be used to enhance the landscaping of the environment in which they are installed. In addition, BMPs minimize runoff and water pollution by maximizing vegetated surfaces. The choice of plant species is essential to ensure the system’s performance, due to their respective properties.

In public spaces, BMPs favor permeable surfaces. For example, the use of porous materials such as cobblestones, gravel or vegetated strips is recommended.

BMP benefits :

• managing increasingly frequent heavy rainfall events and reducing runoff;
• avoiding flooding of buildings and infrastructure;
• improving the quality of water returning to the watercourse and reducing the quantity of pollutants in this water, thanks to sedimentation and biofiltration;
• increased infiltration of water into the soil, helping to recharge the water table;
• reduce the pressure of urban growth on municipal infrastructures and real estate developers.

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Image: Loisirs du parc de la tête d’or