Markham’s Erosion Restoration Program is a long-term plan to restore areas of erosion throughout the City’s watercourses and minimize the risks to private property, public safety, infrastructure and the environment associated with channel erosion.
Erosion is a natural process of ‘wearing away’ of the sides of a channel, and occurs when the forces exerted by the flowing water exceed the resistive forces of the bank and vegetation. This can lead to a change in the shape of a watercourse and is usually caused by an increase in flow. The City is drained by watercourses that can erode due to upstream development, natural processes, extreme weather and watercourse alteration, or some combination of these factors.
Erosion can pose risks to nearby infrastructure (i.e. manholes, sewers, bridges, etc.), adjacent property (due to slope instability) and the ecology of the watercourse itself (from sedimentation, debris build-up and vegetation disturbance).
As erosion is a natural stream process which cannot be avoided, proper maintenance and restoration works should be planned and implemented to minimize risks to public safety. Therefore, it is important for the City to monitor the progression of erosion and evaluate the potential impacts.
With 278 kilometers of watercourses traversing through the City, approximately 27% are within public ownership. For those watercourses under private ownership, the City has easements in many areas along engineered channels to monitor areas of erosion. Over 900 erosion sites are monitored throughout the City. Through the Erosion Restoration Program, the City addresses the risks of erosion to ensure that our watercourses are safe for everyone.
The Erosion Restoration Program is undertaken to identify areas of erosion concern within the City and to develop a plan for addressing erosion. The focus of the study is to identify and prioritize erosion sites, evaluate risk to public health, safety and infrastructure, and develop alternatives for restoration and associated costs.