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Progress report: Canada-wide flood mapping is well underway


June 16, 2021   by Greg Meckbach

The small town of Okotoks was hit hard by the June floods of 2013, with the river valley rushing and raging through wiping out pedestrian bridges, campgrounds, river banks and pathways.

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A nationwide estimate of coastal, pluvial, and fluvial flood hazard is one part of the ongoing effort to come up with a national approach to insuring or re-locating homes at high risk of flood, a federal government official suggests.

Flood mapping is one of five interconnected pieces of residential flood risk management, said Matthew Godsoe, director of the resilience and economics integration division at Public Safety Canada, during the recent CatIQ Connect webinar.

The Task Force on Flood Insurance and Relocation, announced in November 2020, is working on a Canada-wide estimate for flood hazard and flood damage, said Godsoe.

The other four pieces of residential flood risk management are:

  • insurance
  • strategic relocation
  • a review of the Disaster Financial Assistance Arrangements
  • a review of the national disaster mitigation program, which is under a two-year review ending in March 2022.

The task force, including representatives of the Insurance Brokers Association of Canada and the Insurance Bureau of Canada, recently worked with different levels of government to pull together engineering and regulatory flood maps.

“Where we did not have those high-resolution, engineering-level maps, we purchased three global flood models from Aon Benfield, KatRisk and from JBA,” Godsoe said June 10 during CatIQ Connect’s quarterly webinar, produced by Catastrophe Indices and Quantification Inc. “[We] undertook a process of calibrating those against the regulatory maps, so that we could say something intelligent about how accurate they were in comparison to the regulatory maps, [and] to enable us to better describe the level of uncertainty in those estimates.”

The task force also procured address point data and attribute data for all residential properties across Canada. Along with six possible flood insurance models, the task force is handing off the engineering and regulatory maps to an actuarial sciences team that will study them this summer and fall, said Godsoe.

“This has given us very good insights into the total amounts of cost and how they are distributed across pluvial, fluvial, and coastal flood risk,” he said. Also, the process has shown where those total amounts of cost “are distributed [geographically] across jurisdictions, and in which large scale municipalities or rural areas.”

Fluvial flooding occurs when water levels rise in lakes and rivers, the Insurance Bureau of Canada reports. Pluvial (or surface water) flooding happens as a result of heavy rainfall either overwhelming the municipal storm drain system, or from rain falling on hillsides that are unable to absorb the water.

The Task Force on Flood Insurance and Relocation is aiming is to have a “statement of fact report” in order to get a common understanding of flood exposure across country in a given year. It will also examine ways for Canada to create low-cost insurance for residents at highest risk of flooding. The goal is for the statement of fact report to be presented to deputy ministers and made public by spring of 2022, Godsoe said during CatIQ Connect.

An audience member asked Godsoe about coastal flood risk.

“Within one of the models we purchased, we have a full coastal flood damage assessment set,” said Godsoe. “We have been using that to cost out the flood risk. The modelling [for coastal flood risk] is just not quite as mature, but we do have a very significantly annual coastal risk based on the models that we have so far.”

The scope of the insurance scheme under consideration, which is intended to enable affordable coverage for high-risk homes, would include the three big sources of flooding (pluvial, fluvial and coastal), said Godsoe.

“The estimates for coastal are a little bit more rudimentary. The fluvial estimates are really solid and the pluvial ones are quite good.”

Another CatIQ attendee asked whether the flood models factor in defence measures.

“Where there are really big defence structures, and where we don’t have regulatory maps, we have gone through and spot-checked many of those areas,” replied Godsoe.

Generally speaking, regulatory maps do account for large flood defence structures such as the Red River floodway in Winnipeg, Godsoe suggested.

“Unfortunately, for smaller-scale dams and smaller-scale flood defence measures, we do not have a single data layer that we are able pull into the models. So we suspect that many of those things are not currently covered in the modelling approaches.”

Feature image via iStock.com/thefurnaceroom