How Green Infrastructure Can Protect Communities from Flooding

This spring we again witnessed devastating floods in communities across Ontario, costing homeowners and municipalities millions of dollars in damages, uprooting families and businesses, and leaving many wondering if this level of destruction is the new normal. While climate change will continue to cause unpredictable spring rainfall and other impacts, municipal natural assets are emerging as a new class of infrastructure, quickly gaining recognition by municipalities as mitigating flood risk, including here in Ontario.

What are Municipal Natural Assets?
  Municipal natural assets refer to local natural resources such as wetlands, forests and woodlots, parks, lakes, rivers and creeks, that contribute one or more services required for the long-term sustainability of a community and its residents.

While natural assets are often used in concert with traditional engineered or “gray” infrastructure, it is worth noting that when comparing the two, natural assets typically:

• require no or minimal capital expenditures and cost less to maintain;
• are more durable and flexible when managing stormwater flows;
• increase in value over time, while engineered infrastructure depreciates over time.

  In Peel Region, a pilot project demonstrated that municipal natural assets provide stormwater control commensurate with engineered infrastructure. It also demonstrated that natural assets even continued to perform the same level of service under climate change conditions despite higher volumes and velocities of water flow. Using the replacement cost valuation method, the value of stormwater services provided by existing natural assets in the Peel pilot project were estimated to be $704M under current climatic conditions, increasing to $764M under advanced climate change conditions.

Natural assets are not the only kind of green infrastructure that can help mitigate flood risk. Naturalized stormwater management ponds (NSMPs), while engineered, operate using the principles of nature. They are cost-effective to build, less costly to maintain than conventional stormwater facilities, and reduce incidents of flooding, saving homeowners and municipalities money. They also add a great public amenity to neighbourhoods.

How do NSMPs work?
 
Naturalized stormwater management ponds incorporate native plants, including aquatic plants, grasses and forbs, which slow the flow of run-off into the pond while filtering out impurities such as nitrogen and phosphorus, providing many of the same functions as a natural wetland. Currently, 70% of southern Ontario’s natural wetlands have been lost to development, making the addition of human-built naturalized ponds important ecological, as well as infrastructural, investments. After experiencing the benefits of naturalized stormwater ponds, the City of Winnipeg mandated that all new ponds be naturalized and are developing a business case to retrofit existing wet ponds.

Innovation in Ontario’s Greenbelt
 
The Greenbelt Foundation is working with partner organizations to facilitate and support municipal reliance on natural infrastructure. Interest is high across the region. Current projects are listed below and additional initiatives are being developed. Enquiries are welcome.
Opportunities for Municipalities: