The Don River's Flood History

Our ravines guide covers the Don Valley's parkland as it exists today. This page is about how it got that way — a river with a long history of destructive floods, made worse by a century of industrial engineering, and only recently brought back under control.

Early floods and Hurricane Hazel

The Don has a long record of destructive floods and ice jams, worsened over time by urbanization of its watershed — an 1878 flood destroyed more than 20 bridges and mills along the river. But the defining flood event for the whole region remains Hurricane Hazel, which struck on October 15–16, 1954. Hazel dropped enormous rainfall onto an already-saturated watershed; while the Humber River saw the highest death toll, the Don River watershed also flooded severely as part of the same citywide catastrophe that killed 81 people region-wide.

The Keating Channel problem

Well before Hazel, the lower Don had already been drastically re-engineered. A 1909 diversion redirected the river's mouth into a hard right-angle turn, and between 1914 and 1922 the city built the Keating Channel to flush industrial waste and control the river's outflow into the harbour. This channelization created an unintended long-term flood risk: engineers had constrained the river's flow without accounting for how it would behave in a genuinely extreme storm — a vulnerability Hazel exposed and that persisted for decades afterward.

A $1.4 billion fix

The Don Mouth Naturalization and Port Lands Flood Protection Project, led by Waterfront Toronto alongside the city, provincial and federal governments at a combined cost of roughly $1.4 billion, finally addressed the Keating Channel's flood risk — cutting a new, naturalized channel and creating a new island to protect the West Don Lands, South Riverdale and the Port Lands from the kind of extreme flood the old channel couldn't handle. A major construction milestone, completion of the new river mouth and island, was reached in November 2024.

Sources

• Toronto and Region Conservation Authority — Don River Watershed
• Waterfront Toronto — Flood Protection Milestone Puts New Waterfront City Within Reach