New mapping shows how climate change could flood low-lying areas in Vancouver and beyond

Low-lying areas of major cities like Vancouver and Montreal could become inundated with floods in the next 80 years under various climate change scenarios, suggests a floodplains map developed by a Western University researcher.

The maps, created by engineering professor Slobodan Simonovic, are a visual distillation of almost 150,000 reference documents — including current and historical rainfall and snow-melt runoff data, topographic analyses, urbanization factors that impede effective drainage and a range of climate projections.

Simonovic superimposed the data on web-based maps to show potential future flood inundation — how much of an area is covered by water — as well as how often and how significant floods could be.

The maps, which show flood impacts on a Canada-wide scale in a standardized way, identify areas where rivers are most likely to overflow, including the Assiniboine and Red rivers that converge on Winnipeg and the Fraser Valley that runs through Vancouver.

Simonovic said other vulnerable streams are found in parts of northern Ontario, Quebec and British Columbia, the Mackenzie River in Northwest Territories, and much of the island of Montreal.

One of his goals was to show the public the impact of floods resulting from climate change.

“It means basically more land will be flooded, more land will be underwater during these extreme events,” he said, adding that 30 per cent more of Canada could be flooded by 2100, with a flood depth increase of up to 60 per cent.

“Obviously, this is not every location within the country. There are some areas higher risk than others, but an overall increase up to that level is a very significant message.”

Users of the maps can search by postal code and zero in on neighbourhoods, or compare current 100-year flood zones to those forecast under worst-, mid- or best-case climate change scenarios 60 and 80 years from now.