As the Greater Toronto Area expanded and urbanized through the decades, the need to prevent flood damage has steadily grown. It was the catastrophic impact of Hurricane Hazel in 1954 that led to the expansion of TRCA’s responsibilities to include flood control.

Flooding has been a concern for residents of the Toronto area since the area was first settled. Indeed, the first written account of a flood in the region dates back to 1797.

The first severe flood hit the region in 1878. Five inches of rain fell in less than seven and a half hours, causing severe flooding to downtown Brampton and damages to both stores and homes. Bridges were washed out and almost every mill and mill dam in the area was badly damaged or destroyed.

Hurricane Hazel and the Plan for Flood Control and Water Conservation

On October 15 and 16, 1954, Toronto received 210 mm of rain in  a 12-hour period. With steep slopes along rivers and little or no natural water storage capacity, flooding was inevitable. Previous rainfall had already saturated the soils thereby preventing any infiltration, funneling most of the rain directly into watercourses. In the Humber River, flows were four times greater than previously recorded.

For our region, Hurricane Hazel remains the most severe flood in recorded history. In total, 81 lives were lost and thousands of people were left homeless. Most of the bridges on the west side of Toronto were destroyed or badly damaged. Many roads, parks, public utilities, and even an entire street of houses were washed out. While the total economic losses are undeterminable, the tangible damages were astronomical: an estimated $25 million in 1954 dollars.

Hurricane Hazel 1954

Recognizing the importance of flood management, the Provincial government amended the Conservation Authorities Act to enable an Authority to acquire lands for recreation and conservation purposes. In 1959, the Plan for Flood Control and Water Conservation, consisting of three stages, was finalized.

The implementation of the Lands Acquisition Program in 1960 was the first official stage of the plan. The intent of this program was to transfer the liability of flood plain land from private hands to the Authorities and to acquire lands necessary for the construction of flood protection works.

The second stage involved a plan to control flooding through the construction of dams, reservoirs, channels, and other infrastructure. These works, estimated to cost $22,500,000 in the 1959 plan, were designed to control damage in flood prone areas. Finally, the Province initiated an eleven-year process to develop and implement a flood plain planning policy.

Within this process, the Province developed flood plain regulations and updated the Conservation Authorities Act. In essence, flood plain regulations were implemented to restrict future development and land use for flood hazard areas, thereby reducing potential damage and risk to human life.


Between 1959 and 1995 major flood control remedial works were carried out. Of the 15 dams originally identified in the 1959 Plan, the following were constructed:

  • Black Creek Dam in 1959
  • Claireville Dam in 1964
  • Ross Lord Dam in 1973
  • Although not for flood control purposes, Milne Dam was reconstructed in 1964
  • Though not originally identified in the 1959 Plan, an additional flood control dam was constructed in Stouffville in 1969.

In addition, various berms, dikes, and flood control channels have been implemented across the jurisdiction.

TRCA Flood Control structures map

In total, over 18,000 hectares have been acquired through the Greenlands Acquisition Program. This program acquires land for flood and erosion control, as well as the preservation of environmentally significant natural heritage. A significant portion of these lands have been turned over to municipal park departments to manage and now provide for an integrated parks system. The greenspace along each watercourse not only provides social infrastructure but also an area for wildlife to flourish in an increasingly populated area. The lands have become a wildlife corridor not only for permanent species but also for migratory species. What began as a flood control project has helped turn our urban area into a unique, green and beautiful city.

flood control

Today and Tomorrow

Toronto and Region Conservation currently serves approximately on-third of Ontario’s population (over five million). There are approximately 8,000 structures at risk due to flooding across TRCA’s jurisdiction, translating into over 36,000 people at risk at 3.1 billion dollars in potential flood damages, not including potential damage to public infrastructure. TRCA’s role is critical, as its primary function is to protect the public from loss of life and property due to riverine flooding. Its flood risk management activities bridge together flood plain regulation, flood control infrastructure, flood forecasting and warning programs, as well as remediation projects.

With increased urbanization and human impacts on watersheds, flooding will continue to be a significant risk for our region, stressing our need to adapt our flood control policies and procedures. Working together with municipal, provincial and federal governments, community representatives and non-government organizations, TRCA will continue to take a lead role in flood control and water management. We will leverage the most current information available as hydrologic/hydraulic models and mapping are developed, and taking into account the impacts of climate change on these activities.

Hurricane Hazel historical plaque