Stormwater ponds for flood resilience

Stormwater ponds temporarily or permanently hold excess water during heavy rainfall, reducing flooding, erosion, and downstream damage. They increase resilience by controlling stormwater flows, improving water quality, and protecting critical infrastructure. For small and rural communities, stormwater ponds provide a cost-effective way to manage flood risk while supporting community safety and long-term planning.

This guidance outlines key steps, best practices, costing information and case studies to help municipalities plan and deliver stormwater pond projects.

Key steps for successful implementation

• Identify suitable locations: Consider topography, floodplain maps and existing drainage patterns when making decisions about the project site
• Understand your needs: Determine whether a detention (dry) or retention (wet) pond is most appropriate for the site and your objectives
• Centre local priorities: Engage with Indigenous communities, local organizations and landowners to integrate local knowledge and values
• Assess the site: Conduct soil, hydrology and vegetation assessments to guide pond design
• Get your paperwork in order: Seek required permits and approvals from environmental and municipal authorities

Best practices for design and delivery

• Design multi-use spaces: Consider whether ponds could serve as public parks for recreational use during dry periods
• Find secondary stormwater uses: Separate stormwater from agricultural or contaminated runoff to protect water quality and allow for potential irrigation use
• Practice regular maintenance: Extend the life of the pond by being consistent in removing invasive plants, clearing trash and debris, and stabilizing slopes to prevent erosion
• Consider ecosystem benefits: Naturalize the shoreline with a vegetation buffer to improve local habitat, stabilize the banks and enhance the area’s natural beauty

Equity and community considerations

• Implement safety measures: Protect people from accidental injury or drowning by implementing fencing, barriers, gentle grading or signage (this is especially important during winter months when snow may hide unstable pond ice)
• Educate pet owners: Discourage owners from allowing pets to swim or drink from stormwater ponds located in or near off-leash dog parks; ensure owners are aware of the potentially deadly risks posed by strong drain currents and bacteria
• Engage farmers and landowners early: Minimize negative impacts and maximize benefits on livelihoods and property for stormwater ponds near residential and agricultural areas

Costing and budgeting information

Stormwater pond projects can cost $35,000–$75,000 per acre of impervious surface treated for wet ponds. Costs for dry ponds¹ vary by scale and design complexity.

Typical cost drivers include excavation, liner materials, and building outlet structures.

To help reduce overall costs:

• Transplant nearby native plants to reduce landscaping expenses
• Leverage community volunteers for planting and monitoring efforts; provide honoraria where appropriate, particularly for small organizations or equity-deserving communities
• Select sites with natural depressions or existing wetland features to minimize excavation needs

Case studies and lessons learned

Detention pond upgrade improves stormwater management and ecological value (Chilliwack, BC, 2024)

The City of Chilliwack completed improvements to the Teskey detention pond, originally built in 1997, to better manage stormwater from increased development in the area. The project included expanding and deepening the pond, upgrading outlet control structures, planting native species to enhance ecological function, and adding trails and access points for community use.

Lesson learned: Retrofitting existing detention ponds can simultaneously reduce flooding, improve stormwater management, and enhance ecological and recreational benefits. This highlights the value of multi-functional infrastructure upgrades in small communities.

Phased stormwater management enhances flood resilience while planning for future capacity (Town of Sackville, NB, 2019)

Following multiple flooding events, the Town of Sackville constructed a naturalized stormwater pond to store approximately 40,000 cubic metres of runoff and protect homes, businesses and infrastructure in the Lorne Street area. The project was implemented in phases, including road reconstruction, upgraded stormwater and sanitary infrastructure, and the first retention pond, with future plans to add a second pond for additional storage. Community workshops and technical studies informed the design to balance flood risk reduction, ecosystem benefits and long-term resilience.

Lesson learned: Phased implementation allows small communities to incrementally increase resilience as funding becomes available. Real-world testing, such as Sackville’s heavy rainstorm in August 2021, can validate infrastructure performance and reinforce the need for additional capacity in subsequent project phases.

Combining stormwater management with public recreation in sponge parks (Montreal, QC, 2020)

The City of Montreal redeveloped a former marshalling yard into Pierre-Dansereau Park, creating a network of public spaces with integrated stormwater retention. The project included a rain garden, a drainage-adapted playground, abundant native vegetation, and pedestrian walkways. These features allow stormwater to be managed ecologically while providing recreational and community amenities. Community members were actively engaged in the design process, providing input on layout and features.

Lesson learned: Thoughtful, multi-functional design can simultaneously manage stormwater, enhance biodiversity and provide accessible recreational spaces. Early and ongoing community engagement is key to achieving solutions that are both functional and widely supported.

*Note: The case studies included on this page are for informational purposes and were not supported by the Green Municipal Fund.

Additional resources

Water balance model online (Partnership for Water Sustainability in B.C.) – A scenario comparison and decision support tool that helps users model stormwater runoff, rainwater capture and green infrastructure performance at the site and watershed scale. The tool simulates how rainfall moves through surface, interflow and groundwater pathways, enabling planners to design interventions that slow, spread and absorb runoff to protect or restore stream health.

Pond maintenance inspection checklist (Toronto and Region Conservation) – Appendix B of this document provides a detailed inspection form for maintenance and repair of various storm pond components. These include drain valves, vegetation, sediment management, debris obstruction and signage.

Risk management considerations for storm water ponds (Intact Public Entities Inc.) – A guidance resource outlining safety, access control and hazard mitigation measures for municipal stormwater management ponds. It includes recommendations for fencing, signage, vegetation and life-saving equipment.

Explore more flood resilience activities

Learn about other flood resilience project types and how they can support your community:

• Wetland restoration or construction
• Permeable pavements

Return to the Flood Resilience Toolkit for Municipalities 

Related toolkits

GMF offers additional toolkits to support municipalities facing different climate risks. 

• Heat Resilience Toolkit
• Wildfire Resilience Toolkit
• Community Facilities Toolkit

Glossary

Detention pond: A type of stormwater pond that temporarily holds stormwater and releases it slowly to reduce downstream flooding

Floodplain: Low-lying land adjacent to a river or stream that is prone to flooding during high water events

Hydrology: The study of water movement, distribution and quality in a given area, including rainfall, runoff and groundwater flow

Impervious surface: A surface that prevents water from infiltrating the ground, such as pavement, rooftops or concrete

Interflow: Shallow, horizontal movement of water through soil before it reaches streams or rivers

Outlet structure: Engineered feature that controls water discharge from a stormwater pond

Retention pond: A type of stormwater pond that maintains a permanent pool of water while also storing additional stormwater during heavy rainfall

Runoff: Water from precipitation that flows over land surfaces toward streams, rivers or stormwater systems

Sediment management: Practices to remove, control or treat sediment accumulation in stormwater ponds to maintain function and water quality

Stormwater pond: An engineered pond designed to store and manage excess rainwater or runoff to reduce flooding, erosion and water quality impacts

Select resources

1. Dry Detention Ponds | Climate Insight