The City of Toronto is carrying out a study to identify sewer and watermain infrastructure within Mimico Creek that is at risk of damage due to erosion impacts as a result of high flows from storms and snow melt.

This study looks at how the City’s storm sewer and watermain infrastructure can be protected within the creek using recommended solutions to help reduce or prevent future impact. This will ensure the City’s infrastructure continues to operate and service residents and businesses. The solutions will be part of a Mimico Creek Geomorphic Systems Master Plan for the creek that is implemented over a multi-year period.

The geomorphology of a stream examines how natural and human factors have shaped its form and function over time. Erosion can affect the path a stream follows (form) and the aquatic and terrestrial habitats the stream supports (function). Erosion results in gradual changes to the form and function of the stream and stream bed. Significant changes to water levels contribute to increased erosion.

During storm events, rain water or snow melt runoff enters underground pipes via drains and catch basins on streets and in parks and is discharged from storm sewer outfalls into watercourses that flow to Lake Ontario. At times these flows can be high, resulting in erosion damage. High flows from past storms have caused substantial erosion damage to sewers and watermains located in and near the City’s ravines and watercourses.

This erosion damage can:

  • Destabilize the soil near sewers and watermains
  • Expose or break buried sewers and watermains
  • Damage storm outfalls, erosion control structures, the bottom or banks of the watercourse and aquatic habitats

To learn more about erosion in streams and rivers, view the Understanding Streams  information deck.

The map below shows the location of Mimico Creek and area under study.

Arial map of Humber Creek from Hwy 427, north of Airport Road to Lake Ontario

The study area includes the 19 km length of Mimico Creek in Toronto from Highway 427 near Disco Road and Attwell Drive to where it meets Lake Ontario.

Study Purpose

The purpose of the study is to develop a Geomorphic Systems Master Plan (GSMP) for Mimico Creek that will include recommendations for stabilizing the creek and protecting water infrastructure from erosion. The study will:

  • Identify concerns related to erosion that may damage the City’s water and sewer infrastructure.
  • Develop solutions that protect the City’s water and sewer infrastructure from excessive erosion processes within the stream.
  • Improve stream functions, such as increasing stream bank stability, reducing erosion, enhancing stormwater conveyance, and improving habitats.

The study will not examine trail conditions or recommend improvements to trails, forestry or ravine amenities.

Study Process

This study will follow the Municipal Class Environmental Assessment process for Master Plans, an approved planning process under the Ontario Environment Assessment Act. This study includes the following key steps:

  1. Identify the problem or opportunity to be studied.
  2. Identify and evaluate alternative solutions.
  3. Consult the public on evaluation results and study recommendations.
  4. Complete a study report and make it available for public comment.

A Master Plan will be prepared with the final study recommendations. The study report supporting the Master Plan will be posted on the project webpage for a 30-day public comment period. Following a successful public comment period, the recommended solutions will be included in the City’s Stream Restoration and Erosion Control Program and implementation will be prioritized across all GSMPs city-wide.

The study will focus on:

  • Identifying sewers, watermains and outfalls located within the creek that are at risk from erosion caused by high flows from storms and snow melt runoff.
  • Developing, evaluating and recommending solutions to reduce erosion impacts on the City’s infrastructure, while improving aquatic and terrestrial habitats.

In Mimico Creek, there are:

  • 93 sanitary sewer crossings or sanitary sewers parallel to the creek
  • 112 storm sewer outfalls
  • 27 watermain crossings or watermains parallel to the creek


The City will notify and consult the public on the study and its recommended solutions. To stay informed about the study’s progress, please contact us and we will add you to our email list for updates.

In 2021 the City of Toronto carried out emergency work to replace the Van Dusen Boulevard Pedestrian Bridge over Mimico Creek and rehabilitate a portion of Mimico Creek in the area of Van Dusen Boulevard. That work is now complete. Additional needs will be address as part of the Mimico Creek Geomorphic System Master Plan.

To receive project updates by email, please email and indicate that you would like to be added to the mailing list.