Rouge River Tributary 5 Environmental Assessment

The City of Markham has completed a Schedule 'B' Municipal Class Environmental Assessment (EA) study for the Rouge River Tributary 5 watercourse. The study area is a key area for future development and, under existing conditions, the lands around the watercourse have potential flood risks during large storms. The purpose of this study is to assess potential flood mitigation and stormwater servicing for Tributary 5 of the Rouge River, and establish options to provide stormwater management solutions to facilitate future development of lands within the Markham City Centre.

The main Tributary 5 channel generally flows in a northerly direction and connects into the Rouge River. The project study area is primarily bounded the Metrolinx Rail corridor to the west, Highway 407 to the south, Kennedy Road to the east and just north of Unionville Gate to the north. Tributary 5 begins at the southeast portion of the study area at Highway 407 and connects to the Rouge River north of Unionville Gate. Please see the figure below for the study area location.

The comprehensive study and evaluation process has determined that the optimal solution to address potential flood mitigation for the Tributary 5 watercourse is to pipe Tributary 5 underground and have it sized to convey Regional flows. This option will remove flooding potential from virtually all of the Study Area, will open up the development potential of lands that are currently impacted by Tributary 5, and won't displace residents or businesses. The Project’s final report, also referred to as the Project File Report (PFR), documents the Municipal Class EA study, evaluation process, recommendations, impacts and mitigation measures, and a record of engagement.

The final Project File Report is available for download and review under the Documents tab. The Notice of Completion can also be found under the Documents tab.

Get Involved

Public Review Period is Now Open!

We value your input in the development of the optimal solution to address flooding concerns in the Tributary 5 study area. The EA study's final Project File Report is currently available for public review and commenting starting on April 16, 2026, and ending on May 29, 2026, in accordance with the Municipal Class EA process. Please access the Project File Report and the Notice of Completion under the Documents tab. Please provide any comments and/or questions to the Project Study Lead listed on the sidebar.

Previous Public Consultation

A pre-recorded virtual Public Information Centre (PIC) took place from February 25, 2025 to March 25, 2025. The City would like to thank the community for their participation in the virtual PIC.

The virtual PIC presented an overview of the study purpose, existing conditions, evaluation of alternative solutions, the recommended solution, and project next steps. The preliminary recommended option during this stage included piping the majority of the channel to convey the regional storm flows.

Feedback collected during the PIC period has been taken into consideration for the study. A copy of the PIC presentation slides have been provided on this webpage under the Documents tab.

A Notice of the pre-recorded virtual PIC was also sent to stakeholders and members of the public, and is also posted on this webpage under the Documents tab.

Other Ways to Get Involved

1. Stay updated: Save this website to your browser favourites.
2. Provide your feedback: Contact the Project Study Lead listed on the sidebar and provide your feedback or ask further questions you may have regarding the project.