Rouge River Tributary 5 Environmental Assessment

The City of Markham's online engagement website allows you to contribute ideas and feedback on City matters important to you. More information on the project can be found here. 

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 for Tributary 5 of the Rouge River and establish and evaluate options to provide flooding/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 (See Site Location figure below).
 

• Tributary 5 Markham Centre-Notice of Study Commencement.pdf

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. 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 Project File Report is currently available for public review and commenting for a 30-day review period starting April 16, 2026, and ending on May 16, 2026, in accordance with the Municipal Class EA process. Please access the Project File Report and the project’s Notice of Completion here.