Stormwater Management

Wet Weather Flow Management Guidelines

The Wet Weather Flow Management Guidelines provide a practical working aid in the review and approval of stormwater management plans for new development or redevelopment. The guidelines also identify performance objectives for runoff from development sites, flood management, water quality and water balance (or annual runoff volume).

In September 2003, Toronto City Council adopted a Wet Weather Flow Management Policy (PDF), which provides direction on how to manage wet weather flow on a watershed basis. Since that time, proposed developments in the City have had to comply with the policy.

The Wet Weather Flow Management Guidelines (PDF) was developed to:

  • Guide the design and implementation of stormwater management measures necessary to achieve the long-term goals and objectives of the Wet Weather Flow Management Master Plan;
  • Harmonize stormwater management policies and practices of the former municipalities;
  • Provide guidance on stormwater management practices and approval requirements to City staff, industry and property owners.

The City will apply these Guidelines, effective April 1, 2007, for the review and approval of stormwater management plans for new development/redevelopment submissions. The City will also require designs to incorporate water balance, effective July 1, 2007, for all submissions required in the Guidelines. The conditions for completing an application are described below.

While the Guidelines present a general framework of the City's expectations of approval requirements on water balance, water quality and quantity targets for on-site stormwater management, the City also recognizes that flexibility is important for certain site-specific conditions. As a result, the City may consider any innovative approach if it can be demonstrated that there are better ways of achieving the same performance objectives. The Guidelines document is a "living" document, therefore, there will be technical refinements and updates over time.

Any proposed bylaws to enforce new or existing guidelines will be published for a public and stakeholder review when they are completed and before being sent for approval by City Council.


For further information, please contact:

Patrick Cheung, Senior Engineer
Water Infrastructure Management
Toronto Water
Tel: 416-392-7702
Fax 416-338-2828

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