First-of-its-kind map outlines Canada's future flood zones

Map unveils which Canadian cities most at risk of flooding Engineering Professor Slobodan Simonovic discusses Canada's first flood-impact map showing how floodplains may become inundated under various climate change scenarios.

TORONTO — The first flood map of its kind demonstrates how low-lying areas of some of Canada’s major cities could become flooded within the next 80 years.

The maps were developed by Slobodan Simonovic, engineering professor emeritus and flood-control expert at Western University. Spanning the entire country, they predict flood activity over the next 80 years based on various climate change scenarios caused by global warming.

“[This] was the continuation of our interest in understanding better what are the impacts of climate change on natural disasters in general,” Simonovic told CTV News Channel on Sunday. “My part of the project was to look at how flooding will be affected by climate change.”

The interactive maps are a combination of about 150,000 reference documents, including current and historical rainfall and snow-melt data, topographic analyses, and various climate projections. Using web-based maps, Simonovic illustrates flood frequency, depth and inundation in both the present and future.

Major parts of the country that could be affected include parts of Montreal and Vancouver, Simonovic said, among others.

“Across Canada, we are tracing and seeing a lot of locations that may be affected in the future a little bit more,” said Simonovic. “Examples [include] Vancouver with the Fraser River, the lower Mackenzie [River] of Northwest Territories, [and] the Assiniboine and Red rivers in Manitoba.

“They are all showing under the changing climates much higher levels of flood risk.”

It is estimated that about four million Canadians now live in areas that have been affected by flooding. Projections show that these residents and others will be at increased risk of flooding.

This comes as representatives from around the world gather in Glasgow to discuss measures to tackle climate change. A recent report from the United Nations Intergovernmental Panel on Climate Change outlines a clear link between climate change and the occurrence of extreme weather events.

Simonovic points to various factors that are contributing to the magnitude and frequency of extreme weather events in Canada, specifically when it comes to flooding. But the main one, he says, is climate change.

“Precipitation is the main source of the moisture or water, and then there’s conditions on the ground – that means land use and where the rainfall is occurring – and then there’s the previous and current measures that are in place to deal with the distribution of the moisture and so on,” said Simonovic.

“All of these factors are, in a way, affected by our activities and climate change is definitely one of the most significant because it determines the amount of precipitation that we receive.”

Users are able to search the map using postal codes, and can compare current flood zones to future forecasts up to 80 years from now using worst, mid or best-case climate change scenarios. These scenarios depend on whether countries around the world are able to limit their levels of greenhouse gas emissions, and by how much.