Province updates decades-old flood hazard mapping, includes projections to 2100

In a series of presentations given via Zoom last week, the province showed off its new flood hazard-mapping web tool. This marks the first time the province has released new flood modeling since the early 1990s.
“The new maps are state-of-the-art flood hazard maps… [that] provide greater coverage across the province and incorporate the future impacts of climate change with predictions to 2100,” explained moderator Maurice Robichaud.
The interactive map allows users to compare the impacts of different magnitudes of flooding, both in the present and in the year 2100. Also included is a projection of where high tide will lie at the beginning of the twenty-second century. Via the use of its search bar, one may center the map on any region of the province or on an individual property by entering its parcel identification number.
The new maps cover almost the entire coastline and parts of 24 of the province’s rivers. Water resources specialist Jasmin Boisvert noted that some areas of the province’s inland water were excluded due to the prevalence of ice jamming, a process of ice buildup in rivers that can lead to flooding. “Ice jamming is very difficult to predict… the technology isn’t quite there yet, the knowledge isn’t quite there yet, which is why some of these areas of the province… were not mapped.”
Since the last round of flood mapping in the 1990s, there have been smaller-scale projects aimed at updating available modeling, but as Boisvert noted, there was “no provincial-lead initiative of this scale.”
On whether the data has changed significantly in the past three decades, Boisvert observed that some areas “have not changed very much. An example of that would be … the Kennebecasis river in the Sussex area. If you were to look at the old flood hazard maps… the present day [models]… would be very similar.”
Boisvert pointed out one major difference in the modeling, even for areas that have scarcely changed. “We’ve now added this additional information on climate change,” he said. “So those maps are certainly different. That certainly adds maybe thirty [or] forty centimetres of water to those particular scenarios.”
Some areas have seen updated modeling in recent years, including the Fredericton region of the Lower Saint John River. Boisvert said that flood events in 2008, 2018, and 2019 “have really changed the way… that we understand the Saint John River,” and that older maps “didn’t have the benefit… of having those massive flood events.”
When asked how often the new map would be updated, Boisvert admitted: “I can’t really give a concrete answer for that.” However, he assured presentation attendees that “if the new information that we get next year is significantly different than what we know now, then that’s certainly something that would raise a red flag and say ‘okay, maybe we should update this more frequently.’”
“We are certainly committed to updating the information that we have here online as new information comes to light and these climate estimates get refined,” said Boisvert.
Flood risk for properties in Sackville varies widely, although the maps show that in the case of a 1-in-20-year flood, Lorne Street and much of Sackville’s rail lines would be handily inundated.
Sackville’s vulnerability is not a new concern. “We have a lot of our engineering infrastructure that’s in the floodplain,” said Sackville’s Chief Administrative Officer (CAO), Jamie Burke. “Our sewage lagoons, for example,” as well as “a major sewage lift station.”
“It’s really that engineering infrastructure that’s not really movable… those are the areas that we really need to protect,” Burke said.
The CAO noted that dyke rehabilitation is under provincial jurisdiction but is key to protecting Sackville’s infrastructure. The town is hoping for progress to come out of recent studies into the protection of the Isthmus of Chignecto, home to a section of the Trans-Canada Highway and CN Rail lines.
“We’re curious to see what those solutions may be, but certainly a dyke rehabilitation and investment plan is… something that we have encouraged the province to do,” Burke explained.
The province’s new flood hazard map can be found online at: https://geonb.snb.ca/flood_hazard_maps/index.html

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