After July floods claimed four lives, Nova Scotia plans to map floodplains by 2026

After July floods claimed four lives, Nova Scotia plans to map floodplains by 2026

A plan has now been put in place to create the kind of detailed floodplain maps that some Nova Scotia emergency managers said they lacked when heavy flooding occurred in July.

Mapping is expected to take place over the next three fiscal years, with completion by 2026, Byron Rafus, deputy secretary of the Department of Municipal Affairs and Housing, told a legislative committee on Wednesday.

The $10 million program will allow municipalities to identify places where there is a high risk of flooding, and “address issues” related to building homes and other infrastructure in flood-prone areas, Rafus said.

“These plans are being developed for municipal use,” he said in an interview after the session. “They will be given zoning (flood risk) and can plan accordingly and develop rules for their communities.”

The maps will indicate the potential extent of water accumulation in different areas during coastal and inland flooding events.

Mapping uses lidar, a remote sensing technology that creates elevation maps of the Earth’s surface. It also uses other data sources, including surveys of structures such as bridges and culverts, existing data on the depth of rivers and coastal basins, and takes into account water flows, tides and rainfall.

Create models of potential danger areas

This data, combined with climate projections, is used to create models that show potential risk areas for 20-year and 100-year flood events. The maps will show climate conditions in 2050 and 2100.

Two six-year-old boys, a 14-year-old girl and a 52-year-old man died in the West Hants Regional Municipality during floods in July, when heavy rain hit some parts of the county. At the time of the disaster, emergency management officials did not have access to detailed maps of the floodplain, West Hants said.

Mapping of the West Hants area is underway and will be completed by April 1, 2024, Rafus said.

A man in a suit stands in front of the Nova Scotia flag.
Mapping is expected to be done in three phases, Byron Rafus, deputy secretary of the Department of Municipal Affairs and Housing, said during a legislative committee hearing on Wednesday. (Michael Tutton/The Canadian Press)

Tim Webster, head of the Applied Geomatics Research Group at Nova Scotia Community College, said in a phone interview that his group will be involved in mapping work in western Nova Scotia.

“For some municipalities, it will be very valuable because some of them don’t have anything,” he said.

However, he noted that the modeling projections were not as severe as what happened in West Hants, where flash floods swept large trucks off secondary highways. Webster said he thinks it would be wise to include such heavy rainfall events in the mapping as well.

“I think it would be smart to actually try to model the West Hants event and document it perhaps more rigorously than we currently do,” he said.

In a 2020 report by the University of Waterloo’s Intact Center on Climate Change, the authors gave Nova Scotia low marks for flood planning, noting that it is the only province in Atlantic Canada that has delegated mapping responsibility to local governments.

Floodplain maps are useful in showing where water flows during heavy rainfall, and can help municipalities identify areas where they should install infrastructure to divert water, Blair Veltmate, director of the Intact Center, said in an email Wednesday.

Useful flood maps

However, he said floodwater diversion work using strategically located berms, diversion channels, ponds and giant water tanks should be done “in the months and years before major storms.”

“If action is not taken to act on flood map guidance, communities will generally end up deploying thousands of sandbags at the last minute. Sandbags should be the last line of defense against flooding, not the first,” he wrote.

Additionally, Veltmate said there is a danger in citizens putting complete trust in floodplain maps.

“No one—unless they live on top of a mountain—should assume they are free of flood risk just because their home does not appear on a flood map. Small storms, due to climate change, are more common today than in the past,” he wrote. It affects flooding in areas outside the flood plain.

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *