Living in a Flood Vulnerable Area: Downtown Bolton

Notice of Construction

Toronto and Region Conservation Authority (TRCA) will begin work on the Bolton Berm Major Maintenance Project Phase I in September 2020.



In January 2020, Toronto and Region Conservation Authority (TRCA) hosted an open house information session to help residents and businesses in downtown Bolton become better prepared for flood risk. To learn more about riverine flooding in Bolton, just check out the resources from the open house below.


You can download a PDF copy of the panels, or view the panels using the document reader below. Select Read Now for a full-screen view; select the arrow to the right to advance to the next page.

Use the information on this page to help you understand and prepare for flooding if you live near Bolton in the Town of Caledon.


The majority of downtown Bolton is within the floodplain of the Humber River, and is susceptible to flooding. Toronto and Region Conservation Authority (TRCA) ranks Bolton among the top 10 Flood Vulnerable Clusters (Read definition) in our jurisdiction.

The cluster is a designated SPA, or Special Policy Area. (Read definition.)

Do You Live in an Area at Risk of Riverine Flooding?


If you’re not sure whether your home is in a floodplain, use TRCA’s map viewer to find out. Just enter your address in the search bar. If your home lies within the shaded areas, you could be at risk of flooding.

map showing floodplain area in Bolton

Use the Map Viewer Now


Flood risk map for Bolton Core


NOTE: TRCA utilizes the best technology and latest available data in preparing floodplain mapping. As modelling techniques continue to evolve and as new information continues to be gathered, the resulting updated floodplain mapping products can change the risk and damage calculations, as well as the ranking of TRCA’s flood vulnerable clusters in the future. Map data generated December 2018.

Disclaimer: The data used to create this map was compiled from a variety of sources and dates. TRCA takes no responsibility for errors or omissions in the data and retains the right to make changes and corrections at any time without notice. For further information about the data on this map, please contact the TRCA GIS Department. Return period scenarios are based on statistical probabilities which may be exceeded. Flooding can also occur in areas other than identified on this map.

Understanding Flood Risk in Bolton


Flood Vulnerable Cluster: An area within the floodplain with a high concentration of buildings and roads that could be impacted by riverine flooding.

Special Policy Area (SPA): An area within a community that has historically existed in the floodplain and where site-specific Provincial policies are intended to provide for the continued viability of existing uses.

The downtown area of Bolton was historically developed around river-based mill industries, long before the advent of land use management practices designed to reduce flood risk.

Today, the downtown Bolton community is susceptible to flooding as a result of heavy rainfall events, the spring thaw, and — as experienced in early 2019 — ice jams.

The Bolton Flood Vulnerable Cluster is located in the vicinity of Highway 50 and King Street.

While the Bolton berm and channel have provided functional flood protection for most rainfall events, the flood event of March 2019 demonstrated the risk associated with ice jams in this area.

photo of ice jam in Bolton from March 2019

Historically, ice jams in Bolton have occurred in the river reaches of Hickman Street (west of Queen Street), King Street and Old King Road, and Sneath Road, downstream to Albion-Vaughan Road.

Learn more from TRCA about flood risk in general HERE.

What Types of Flooding Can Affect Bolton 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, which 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 Bolton Can Happen at Any Time of Year

winter icon WINTER: Ice Jams. When temperatures and/or water levels rise, river ice breaks into large chunks. These chunks can become jammed at bridges or other obstructions. Rivers can become backed up and can overflow their banks.
spring icon SPRING: Spring Thaw. Accumulation of snow during the winter season can lead to flooding during the early spring if conditions are right. When temperatures rise, snow melts and turns to runoff.
summer icon SUMMER: Thunderstorms. Thunderstorms can bring large amounts of rain in a short period of time. These intense, localized downpours can lead to flash flooding.
fall icon FALL: Seasonal Weather Systems. Large wet weather systems, including tropical storms such as hurricane remnants (like Hurricane Hazel in 1954), can last for several days. This prolonged and heavy precipitation, on top of already saturated soils, can cause rivers to rise.

Flood Protection in Downtown Bolton

Bolton Berm: How Flood Infrastructure in the Area Works

In the early 1980s, TRCA constructed a network of berms and a flood control channel in downtown Bolton from Highway 50 to King Road.

Berms were built along the south bank of the river to prevent flood water from entering the Bolton core. A flood control channel was constructed under Humber Lea Road to bypass the oxbow section of river.

A culvert was placed under King Road to help regulate the release of water to the oxbow (curved) section of the river.

When high water flows are present, most of the water flows through the flood control channel. This reduces the risk of flooding for the homes around the bends in the river.

view of Bolton Channel from the south bank
view of Bolton Channel looking downstream
view of Bolton Channel looking downstream
view of Bolton Channel near Highway 50

Learn more about TRCA’s flood control infrastructure HERE.

Flood Protection Update

What You Need to Know About the Bolton Berm Major Maintenance Project Phase I

Why is TRCA doing maintenance on the Bolton Berm?

In 2016, TRCA hired an engineer to investigate the Bolton Berm. The berm was found to be too small to protect against the 500-year flood.

This is because the information available when the berm was built in the 1980s was limited. Our ability to predict how floods maneuver through a river system has improved substantially over the past 40 years. In 2016, TRCA was able to apply digital mapping, updated rainfall data, and modern hydraulic modelling software to test the berm.

The engineer’s study determined that, in some areas, the water elevation of the 500-year flood is higher than the top of the berm, and that the berm would overtop during this storm event. The engineer also found that more erosion protection for the berm is required.

Bolton Berm Phase 1 construction area and entrance
Phase I construction area and entrance.

What work is TRCA doing on the berm?

TRCA will be increasing the height of the berm by removing the topsoil and adding compacted, engineered fill. Stone will be added to the river side of the berm to protect it from erosion. The berm will be raised 20 to 70 centimetres, depending on the location along the crest.

Restoration will include seeding the berm with grasses and planting riparian shrubs along the riverbank.

Because the berm is very long, TRCA will be conducting this work in phases:

  • Phase I: the berm will be repaired between 181 King Street East and 211 King Street East
  • Phase II: the section of berm between Queen Street and Humber Lea Road

When will this project start?

TRCA will start the Phase I work on the berm in September 2020. The work is scheduled for completion in April 2021.

It is expected that Phase II will begin in 2021, although the exact date is not known at this time. Residents will be informed when Phase II is scheduled to commence.

Will this construction prevent ice jams?

This project addresses the flood risk associated with high flows in the river. It will not prevent ice jams. However, increasing the height of the berm will reduce the risk of overtopping due to ice.

Enhanced monitoring for ice jam potential is the most effective method for reducing risk. For more information, please refer to the presentation, panels, and Q&As from our January 2020 open house.

aerial photograph of ice jam in Humber River in Bolton during Feburary 2019
Ice jam in the Humber River in Bolton, February 2019.

Why do all the trees on the berm need to be removed?

TRCA must remove the trees on the berm to enable construction crews to raise the berm with new material. Once construction is completed, the berm will be re-planted with new grass.

In the future, TRCA will remove any trees that start to grow on the berm, because their roots can weaken the berm. If a tree blows over, the root system can also rip up large areas of the berm.

To compensate for the removal of trees from the berm, TRCA will plant new trees in the surrounding area, particularly the north bank of the Humber River across from the berm. While most of the trees currently growing on the berm are invasive Manitoba maples, the new trees will be native species.

In addition, TRCA will plant shallow root shrubs on the river side of the berm to provide riparian habitat.

How will TRCA crews access the berm in Phase I?

TRCA will access the berm from the west side of 181 King Street East. Please refer to the map above.

Residents in the area can expect to see increased activity, as trucks and heavy equipment access the berm. The contractors will reduce vehicle speeds to ensure public safety and minimize dust, while restricting work to daylight hours to comply with the noise bylaw.

For site safety and to limit the potential spread of COVID-19, access to the site will be restricted to construction workers, staff, and suppliers for the duration of the project. TRCA requests that members of the public adhere to all posted signage.

soil sampling on the Bolton Berm
Soil sampling on the Bolton Berm.

Do I have to remove items from my yard that are on the berm?

Please remove any items currently on the berm, as these encroach on TRCA property. Fences, picnic tables, planters, and other items need to be removed so that construction crews can access the berm.

Residents who have been identified as having items on the berm should have received a letter from TRCA with details about removal.

COVID-19 Safety

TRCA is committed to the safety of workers and members of the public. Unfortunately, due to the current situation, a public information session cannot be held.

TRCA is working on robust safety programs, and our staff and contractors are collaborating to implement specific site work practices to protect against the spread of COVID-19.

All TRCA staff will practice physical distancing, wear appropriate personal protective equipment (PPE), and work in accordance with the Province’s sector-specific guidelines for construction.

To speak with the project manager, please contact:

Rudra Bissoon, B.E.S. (Hons.), M.E.S, CAN-CISEC
Project Manager, Erosion Risk Management
Engineering Projects | Restoration and Infrastructure

How Will I Know If Flooding In Bolton 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.



When it comes to flood preparedness, everyone — homeowners, landlords, renters, and condo owners — has a role to play. You can take steps to prepare; just select a category below to find out more.

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
• Town of Caledon    
• Region of Peel    
• Peel Regional Police    
• Ontario Provincial Police (OPP)
• OPP Traffic Updates
• Brampton Transit
• GO Transit
• 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