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Lake Simcoe Region Conservation Authority

Skip Navigation LinksLake Simcoe Region Conservation Authority > A New Way to Manage Stormwater

​​A photo of a municipal stormwater pond.​​​

A New Way to Manage Stormwater

​We've been engaged in a ground-breaking research study in an effort to improve stormwater management (SWM), introduce savings, and address the impacts of urbanization, degraded water quality, flooding and climate change.

The project, “Equitable Responsibility for Transformative Design: A systems-based approach to watershed management" demonstrated that improved environmental outcomes can be achieved at lower costs if stormwater is planned at a watershed-scale and considers the use of both publicly and privately owned lands.

A summary report can be accessed here​ and the full technical report can be provided by contacting communications@LSRCA.on.ca.

Now that we have completed the study and it's shown us the many benefits of changing how we manage our stormwater, we are working with municipalities and other stakeholders on a plan to put these changes in place.


​Stormwater management is primarily the responsibility of municipalities who plan and execute stormwater management within their jurisdiction, usually with little consideration of impacts to downstream municipalities, or cost savings that could be achieved by working collaboratively. In addition, most municipalities have not been able to allocate the necessary funds to manage stormwater because of competition with other priorities.

These inefficiencies together with inadequate funding has led to a $6.8 billion stormwater infrastructure deficit in Ontario alone.

This pilot project was undertaken in the East Holland River subwatershed to show how stormwater management can be optimized to reduce phosphorus loads and river flow (including flooding) at the lowest cost. In this study it was important to seek optimal use of Low Impact Development (LID) solutions as well as centralized solutions (e.g.hybrid ponds) considering availability of both public and private lands.

What have we learned?

This project tells us what we have known for some time now, ​​that being the need to look at stormwater through a watershed lens. It demonstrates the multiple benefits of undertaking a watershed scale modeling approach. 

Through the study a stormwater methodology was developed for the East Holland River subwatershed that can be further refined and applied to other subwatersheds within the Lake Simcoe watershed and beyond.

Key findings:

  • Identified the most cost-effective stormwater control measures to achieve a 40% reduction in phosphorus load.
  • Achieving a 40% reduction in phosphorus load is only possible if SWM controls are sited on both private and public lands.
  • There is the potential of a 27% cost saving if stormwater management is planned at watershed scale vs jurisdictional scale.
  • Phosphorus reduction strategies also reduced peak flows, leading to a 17- 24% reduction during a 25-year storm event.
  • Optimized solutions will help reduce impacts of climate change. For example, nearly all the projected increase in a 1 in 10-year peak flow event would be mitigated by the optimized SWM solution.  

For more information on this project please ​contact: Ben Longstaff b.longstaff@lsrca.on.ca​

Project Partners

  • Town of Aurora
  • Credit Valley Conservation Authority
  • Town of East Gwillimbury
  • Fortin Economics
  • Freeman Associates
  • Ministry of Environment, Conservation and Parks
  • Town of Newmarket
  • Paradigm Environmental 
  • Sustainable Technologies Evaluation Program
  • Toronto and Region Conservation Authority
  • Town of Whitchurch-Stouffville
  • York Region