Basement Flooding

What the City is doing: Basement Flooding Protection Program

Toronto’s sewer systems were designed for most storms. However, Toronto is experiencing more severe storms, with more rain falling over a short amount of time. This increases pressure on the sewer systems and overland drainage routes such as roads, local rivers and streams. When severe storms occur, the sewer system and overland drainage routes can become overloaded, leading to basement flooding.

The City's Basement Flooding Protection Program is a multi-year program that is helping to reduce the risk of future flooding across the city by making improvements to the City's sewer system and overland drainage routes. This involves:

  • Carrying out Environmental Assessment studies in basement flooding study areas across the city
  • Constructing recommended infrastructure improvements on a priority basis


On this page:

Environmental Assessment (EA) Studies

For each basement flooding study area, an Environmental Assessment (EA) study is conducted.  These are complex studies that can take two or more years to complete. 

The EA studies examine the ability of the sewer system and overland flow paths to safely carry stormwater runoff during severe storms and recommend infrastructure improvements to increase the capacity of the sewer system that will reduce the risk of future flooding.

Improvements may include:


Each study is being carried out in accordance with the Municipal Class EA requirements. An EA defines the problem, considers and evaluates alternative solutions, assesses impacts of the proposed solutions, and identifies measures to lessen any adverse impacts. Consultation with the public and interested parties is an important part of the EA process. The public and interested parties can provide input into the planning process at key stages of the study process.

For more information about a current or completed Basement Flooding Environmental Assessment Study, visit the Activities at a Glance section.

From Studies to Construction

Once an EA study for a basement flooding study area is complete, the recommended basement flooding projects are sequenced into a 5-year project list which is presented on an annual basis to City Council.  As all projects cannot be constructed at the same time, projects are prioritized and scheduled to protect the greatest number of properties as soon as possible, within approved budgets, and coordinated with other construction work -- as per Council approved criteria. The length and type of construction will vary depending on the type of projects being implemented.

There are several stages of work that must be undertaken before a construction project is completed.  The stages include:

  1. Preliminary Design:  Preliminary engineering drawings are developed for review and input from City departments, utilities and regulatory authorities.  The input is incorporated in the overall design.
  2. Detailed Design:  Final detailed engineering drawings are developed and permits to proceed with the construction work are obtained.  Prior to construction, Public Notices are delivered door-to-door about two months in advance to let the community know that a construction project will soon be taking place.
  3. Construction:  Construction Notices are delivered door-to-door about two weeks in advance and road signage is placed in the community to provide residents with project details prior to the start of construction. Construction activities may include excavation of the roadway, sidewalks and/or boulevards, and may require protective fencing to be erected.
  4. Restoration  Restoration within construction areas varies by project, and typically involves restoration of road surfaces, sidewalks, grass and tree plantings, etc.


For more information about current basement flooding construction projects, see the Activities at a Glance section below.

Working with the community

The City of Toronto and its contractors are committed to communicating with local communities about basement flooding construction activities and anticipated disruptions in their neighbourhood.

The Basement Flooding Protection Program has a Field Ambassador who is dedicated to communicating with the local community and the on-site contractor, and responding to construction enquiries during the course of the project. You may spot the Field Ambassador on your street in a brightly coloured blue vest.

Field Ambassador contact information is provided in the Construction Notice for each project. the Construction Notices are available on the City's Construction Information website.

Basement Flooding Protection Program: Activities at a Glance

The Basement Flooding Protection Program will examine the entire city. EA study area boundaries are defined by "sanitary subsewersheds" (i.e. areas that are serviced by the same local sewer infrastructure) and are prioritized based on past flooding experiences.

View the interactive map that shows the different basement flooding study areas across the city. Enter your address to find out more about what is happening in your neighbourhood.

  Click here to view the map.

Experiencing Basement Flooding?

If your basement floods, please contact 311 (24 hours/day, 7 days a week) immediately. You can call, e-mail or submit a self-service request and a City staff member will come to your property to investigate. If you are calling during a severe storm event, please note there may be high call volumes and some delays; we appreciate your patience.

Contacting 311 helps the City keep track of flooding incidents and is part of the critical information used when planning and prioritizing basement flooding study areas. Please note that the information collected by 311 is not shared with any third party including insurance or real estate companies.

More basement flooding prevention tips and advice.