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Don Mills Channel Flood Reduction

Don Mills Channel Flood Reduction

As part of Markham’s Flood Control Program, a Class Environmental Assessment was initiated on the Don Mills Channel. 

The Don Mills Channel is a small man made channel that runs through the commercial/industrial area in the Woodbine Ave and Denison Street area.  Several of the private properties and roads in this area are prone to flooding during large storm events. 

The environmental assessment aims to:

  • Identify and understand the causes of flooding in the study area
  • Develop a range of alternative solutions to reduce flooding and flood damages from the Don Mills Channel
  • Recommend the preferred solution or suite of solutions to best reduce flooding and flood damage
  • Establish the funding, approvals and other activities needed to implement  the recommended solutions.


The current system of open channels and culverts does not have adequate capacity to handle storm water runoff during large storm events. Businesses surrounding the Don Mills Channel have flooded numerous times since the land was developed in the 1970’s. Major roads in the study area, including Woodbine Avenue, can be impassable during severe storms.

The Don Mills Channel study area was realigned and confined to a relatively narrow channel corridor through urban development. Significant portions of the Don Mills Channel were also piped through some of the older development sites in the study area.

Study Area

Download a high resolution PDF of the study area

Don Mills Channel Study Area

Estimated Flooding

This image shows the predicted extents of flooding from the August 19, 2005 storm event within the study area, and pictures taken during and shortly after the storm.

Don Mills Channel estimate flooding area

Project Schedule

Fall 2016
  • Liaison committee meeting with key stakeholders to review existing conditions Public Information Centre (PIC) #1
  • Development of initial flood reduction alternatives
Spring 2017
  • Liaison committee meeting to review of alternative solutions and the evaluation process
  • PIC #2 to present the alternative solutions and evaluation results
  • Selection of the preliminary preferred alternative
Summer 2017
  • Council presentation
  • Confirmation of the preferred alternative
Fall 2017
  • Notice of Completion
  • File project with the Ministry of the Environment and Climate Change
Spring 2018
  • A Phasing Plan for the design and construction of all recommended flood protection works will be created
  • Design and construction of lower cost immediate improvement projects to begin

Documents, News & Resources

Process for Project Municipal Class Environmental Assessment

Class EA Phase 1

Identify Problem or Opportunity

  • Identify Need
  • Initiate Consultation with the public and agencies
  • Notice of Commencement

Background Review

  • Obtain and review background documentation and initiate agency contact
  • Identify data gaps to be address during the site inventory/ investigation

Class EA Phase 2

Site Inventory / Investigation

  • Undertake natural heritage investigations
  • Aquatic habitat assessment
  • Incidental wildlife survey
  • Undertake hydrology/hydraulics investigation
  • Archealogical Investigattions
  • Identify opportunities and constraints
  • PIC #1

Evaluation of Alternatives

  • Identify alternatives
  • Complete impact assessments
  • Evaluate alternatives
  • Select preferred alternative
  • Preliminary Design / Project File Report

Preliminary Design / Project File Report

  • Preliminary design of preferred alternative
  • Recommendation for further study, if required
  • PIC# 2
  • Develop a  staging and implementation plan
  • Prepare Project File Report
  • Notice of Completion
  • 30-day Public Review


Detailed Design / Implementation

  • Detailed design of the proposed works
  • Obtain permits and approvals
  • Prepare contract drawings and tender documents
  • Construction and operation of the works
  • Post-construction monitoring

View a detailed Class EA Process for municipal infrastructure projects 

Get Involved

You can get involved in the planning process by attending public information meetings which will take place throughout the process. Sign up for our email list by contacting one of the managers below to stay informed throughout the project.  


Robert Grech, P.Eng.,
City Project Manager, City of Markham,
8100 Warden Ave., Markham, ON L6G 1B4
905-477-7000 ext. 2357 |

Steve Hollingworth, P.Eng.,
Consultant Project Manager, The Municipal Infrastructure Group Ltd
8800 Dufferin Street, Suite 200, Vaughan, ON L4K 0C5
905.738.5700 ext. 359 |