City of Toronto potential flood area, for a 50 foot or 15.25m rise in water level from Lake Ontario, which occurred in Houston 2017 hurricane Harvey. Map changes by Don Tai
I was wondering, I am sure like many others, what would happen if the City of Toronto had a flood similar in height to Houston 2017 caused by Hurricane Harvey. Who would get flooded and who would remain dry? Is the City of Toronto largely at risk? Are we ready? Unlike Houston, Toronto is not flat. We also do not have hurricanes or tropical storms. That being said, let us try to analyze a topological map of Toronto and see how we would fare. As I live in Scarborough note that Scarborough has the Scarborough bluffs. My area of Scarborough is 235m above sea level. As Lake Ontario is 75m above sea level, we have a buffer of 160m or 525′. I think we are safe from a flood risk.
Lake Ontario is 75m above sea level. The City of Houston received 20′-50′ or 6.1m-15.2m of flooding. This means, theoretically any piece of land below 90m in Toronto might have been flooded. We also assume that Toronto would have similar drainage characteristics as Houston. I would find a topographic map of Toronto, find out who is below 90m and this would be the areas of Toronto that would be flooded.
City of Toronto topological map, flood risk
From my rough estimate of Toronto topology, and specifically this Toronto map a 50′ or 615m rise of Lake Ontario would flood any land below 90m.
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City of Toronto flood map, finer detail of downtown Toronto
City of Toronto topological map. If waters did rise as in Houston of 50′ or 15m, all the blue areas would be flooded.
City of Toronto topological map. If waters did rise as in Houston of 50′ or 15m, Scarborough, mostly in red at above 200m, would be far higher than the 90m flood high water mark.
City of Toronto topological map overlayed with a Google street map. If waters did rise as in Houston of 50′ or 15m, Scarborough, mostly in red at above 200m, would be far higher than the 90m flood high water mark.
There are no clear lines here, and no one can predict how much rain can fall, how much water will rise and how quickly rainwater could be absorbed by the ground. A guess would be that Queen Street from the Gardener through to roughly Spadina, and Gerrard from University past the Don Valley Parkway through to the Lake. That is a sizable portion of downtown Toronto. For certain all of the Gardener Expressway and the Don valley Parkway south of Eglinton Ave would be the first to flood. These roadways, as well as train lines are built on low land and are at very high risk of flooding. We have already seen in Toronto the DVP south of Bayview Avenue being flooded in 2013 and 2017. This flooding was from regular rainstorms.
Toronto Don Valley Parkway flooding in 2013
City of Toronto potential flood area, for a 50 foot or 15.25m rise in water level from Lake Ontario, which occurred in Houston 2017 hurricane Harvey. Map changes by Don Tai
