Living in a Flood Vulnerable Area: Markham Industrial

Use the information on this page to help you understand and prepare for flooding if you are a private property owner in the Markham Industrial area.


Located within the Don River watershed, the Markham Industrial cluster is in the City of Markham, part of the Regional Municipality of York. It is situated near the intersection of Woodbine Avenue and John Street and west to Highway 404.

Are You in an Area at Risk of Riverine Flooding?


If you’re not sure whether your property is in a floodplain, use Toronto and Region Conservation Authority’s (TRCA) map viewer to find out. Just enter your address in the search bar.

If your property lies within the blue shaded areas (as shown below), you are within the floodplain and could be at risk of flooding.

map viewer showing Markham Industrial flood vulnerable area

Use the Map Viewer Now

Understanding Flood Risk in Markham

The Markham industrial cluster is subject to flooding because 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 1970s. Major roads in the study area, including Woodbine Avenue, can be impassable during severe storms.

The neighbourhood experienced significant flooding to private properties and roads during a storm event on August 19, 2005. Spills can also occur in nearby low-lying areas:

  • During a 2-year storm, a spill can occur at the Mayfair Club at 50 Streelcase Road East and the adjacent commercial properties located at 100 Steelcase Road.
  • During a 5-year storm, the commercial properties on Torbay Road can also be inundated, along with the Courtyard by Marriott Toronto Northeast/Markham.
  • Several other private properties and roads in this area are prone to flooding during large storm events.

The City of Markham completed an Environmental Assessment in 2018 to determine the most appropriate means of flood protection from frequently occurring storms for properties along the Don Mills Channel. The project, which is currently in the implementation phase (targeted for completion by the end of 2027), includes the following components:

  • A Flood Control Storage Facility
  • Culvert Upgrades
  • A Floodproofing and Education Program

The objective of the floodproofing and education program is to assist property owners and managers, as well as tenants, to identify and implement measures to protect their properties and assets against flood damage.

Learn more from TRCA about flood risk in general HERE.

What Types of Flooding Can Affect Markham Residents?

Did you know that there are several types of flooding? Different levels of government are responsible for different types of flooding. To find out who to contact during a flood, see BE PREPARED.

  1. Riverine flooding occurs when the water levels of rivers rise, overflowing their banks. Reducing riverine flood risk is under the mandate of Conservation Authorities like TRCA.
  2. Urban or Pluvial flooding consists of street flooding, basement flooding, and flooding of other low-lying areas due to the overflow of local drainage systems. Municipalities are responsible for managing this type of flooding.

Flooding in Markham Can Happen at Any Time of Year

winter icon WINTER: Ice jams can occur behind crossings and at bends in rivers, causing water levels to back up behind the jammed ice.
spring icon SPRING: Cummer Creek can experience high flows in the spring as rainfall and melting snow add flows to the river.
summer icon SUMMER: Parts of Cummer Creek can flood when intense, localized, downpours occur with summer thunderstorms.
fall icon FALL: Large wet weather systems, often the remnants of tropical storms (like Hurricane Hazel in 1954), can last several days. Prolonged and heavy precipitation on top of already saturated soils can cause rivers to rise.

How Will I Know If Flooding In Markham Is Forecasted?

  • TRCA operates a Flood Forecasting and Warning Program. If flooding is possible or about to occur, TRCA issues flood messages to designated individuals within municipalities, local agencies, school boards, the media, and members of the public who self-subscribe. LEARN MORE

Floods Happen graphics

  • TRCA maintains a network of river and rainfall gauges. You can get real-time gauging information HERE.

Flood Protection Near Markham

The Don Mills Channel is a small, man-made channel that runs through the commercial/industrial area in the vicinity of Woodbine Avenue and Denison Street. It is managed by the City of Markham. LEARN MORE.

Learn more about TRCA’s flood control infrastructure HERE.


Floods are the most common natural hazard in Canada, and the most costly in terms of property damage. You can take steps to prepare for a flood and reduce the likelihood of damage.

1 Know the Risks
Be aware of the types of hazards that might affect your property, and the kinds of emergencies that could be expected.
2 Make a Plan
Have an emergency plan for your property. This will save time and make real situations less stressful. View the City of Markham’s emergency response plan HERE.
3 Get a Kit
In an emergency, you will need basic supplies, and should be prepared to be self-sufficient for 72 hours. The City of Markham has developed great resources to help you to create your own kit. Learn more HERE.
4 Talk to Your Insurance Provider
Overland flood insurance is not a standard offering on most policies. Talk to your representative to confirm your coverage and options. You can learn more from the Insurance Bureau of Canada HERE.
5 Protect Your Property
There may be steps you can take to make your property less vulnerable to the effects of flooding, such as installing backflow preventers and ensuring that elevators don’t descend into flood waters. Check out the resources offered by the Intact Centre on Climate Adaptation HERE.

Flood Preparedness Tips for Property Owners


  • Put weather protection sealant around basement windows and the base of ground-level doors.
  • Consider installing a sump pump and zero reverse flow valves in basement floor drains; and make sure everything is working and has a battery back-up.
  • Clear eavestroughs, catch basins, culverts, and drainage ditches.
  • Review your insurance policy to ensure you are adequately covered. (See above.)
  • Do not store important documents or valuables in the basement.
  • Assemble a 72-Hour Emergency Kit. (See above.)


  • Move furniture, electrical appliances, toxic substances (such as pesticides and insecticides), and other belongings to a floor above ground level.
  • Do not attempt to shut off electricity if any water is present.


  • Listen to the radio to find out what areas are affected, what roads are safe, where to go and what to do if the local emergency team asks you to leave your home or business.
  • Never cross a flooded area:
    • If you are on foot, fast water could sweep you away.
    • If you are in a car, do not drive through flood water or underpasses.
  • Avoid crossing bridges if the water is high and flowing quickly.


Tips to ensure building safety:

  • Do not return home or enter your business until authorities have advised that it is safe to do so.
  • Make sure the building is structurally safe.
  • Look for buckled walls or floors.
  • Watch for holes in the floor, broken glass and other potentially dangerous debris.

Who to Contact During a Flood

who to contact during a flood in York region

Select the image above to download a PDF copy.

Municipal Flood Resources

Check out the following to help better protect yourself and your home:



Additional Resources for Property Owners

  • Use York Region’s Business Continuity planning guide to prepare your business for any emergency. Learn more HERE.

Get more preparedness tips from TRCA HERE.


Use the following sources to stay informed during a flood:

• Check your local weather online, or on radio or television before you leave the house.
• Check Environment Canada’s public weather alerts
• Sign up to receive TRCA flood messages
• Check your local municipal and public transit social media links (below).

Social Media Alerts and Notices

• TRCA Flood Risk Management
• City of Markham    
• York Region    
• York Regional Police    
• Ontario Provincial Police (OPP)
• OPP Traffic Updates
• York Region Transit
• GO Transit
• York Region News    
• 680 NEWS
• CBC Toronto (traffic reports)

Additional Resources

Emergency Management Ontario
• Ontario’s Emergency Management and Civil Protection Act: Disaster Recovery Assistance for Ontarians
• Public Safety Canada:

Flood Smart CanadaCreated in partnership with the Insurance Bureau of Canada, this resource is designed to help Canadians better prepare for flooding.
• Electrical Safety Authority: Flood Safety Information
• Intact Centre on Climate Adaptation: Flood Protection Resources
• Institute for Catastrophic Loss Reduction: Protect Your Home from Basement Flooding

Information About Flood Insurance