The Toronto Rain Storm 2005

A clear example of the destructive power of stormwater was demonstrated during an extremely heavy rain event that hit Toronto on August 19^th 2005.  During a 2 to 3 hour period that day an enormous quantity of rain fell in the Greater Toronto Area.  Some rain gauges recorded over 150 mm of rain.  Stormwater accumulated so fast during the storm that many storm sewers were overwhelmed, causing a chain reaction of backups and flooding across the city. 

The most dramatic result occurred in North York where a small culvert that previously allowed Black Creek to pass underneath Finch Street was quickly overwhelmed by stormwater.  The enormous force of the water that built up behind the road tore a 6 m wide by 3 m deep trench through the road.  Three other roads were also damaged in the storm, as was a wastewater plant and a sewer main.

This single rain event cost the city an estimated $34 million, including $6 million for the immediate repair of Finch Avenue, $9 million for cleanup and repair of surrounding parks, and over 1,600 over-time staff hours.  The environmental clean up cost to mitigate the effects of a broken sewer main that ruptured during the storm, (releasing raw sewage into a nearby stream at 7cubic meters per second), may incur additional costs.  The insurance bureau of Canada estimates over $400 million was paid out to private citizens to cover flood damage to basements from this storm.  All told, the cost of damage from this single rain event was astronomical. By pushing the stormwater system past its capacity these events will only become more common.

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