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Seawall damage a sign of things to come amid sea level rise and climate change, experts warn

The extensive storm damage to parts of Vancouver and West Vancouver’s waterfront on Friday may be a sign of things to come amid climate change and rising sea levels, experts warn.

Parts of the Stanley Park and Ambleside Park seawalls were left looking like they’d been hit by an earthquake after strong winds helped produce a storm surge at the same time as a seasonal king tide.

Stanley Park seawall heavily damaged during king tides

Stanley Park seawall heavily damaged during king tides

SFU earth sciences professor, John Clague, said the combination of those two factors was exacerbated by sea level rise, and that similar damaging storms are expected to increase in frequency in the years to come.

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“It’s a double whammy because you’ve got sea level higher, but you’ve also got the cyclic king tides stacked on top of that, which means that the types of event we saw on Friday are going to become more common and they’re going to be more damaging,” he said.

According to the U.S. Global Change Research Program, the global sea level has already risen by between 16 and 21 centimetres since 1900 — and the rate is increasing. About seven centimetres of that rise accrued in the last 29 years.

Estimates vary on how fast oceans will continue to rise, but the federal 2019 Changing Climate report projects the Vancouver area will likely see more than 50 centimetres in growth over 2000 levels by century’s end.

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The B.C. government has advised municipalities to plan for a sea-level rise of 50 centimetres by 2050 and one metre by 2100.

“The sea level globally is slowly, slowly rising. Most people would not be aware of that because we have daily tidal fluctuations that go through four to five metres, so you’re just not aware this is happening slowly but persistently,” Clague said.

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“But later in the century we’re going to see the plane of the sea is anywhere from about 30 centimetres to a metre from where it is today.”

When construction on Vancouver’s seawall first began in 1917, its designers never anticipated the conditions it is contending with today, according to architect and urban planner Michael Geller.

“While it was built to the standard of the day, they never contemplated there would be the level of sea-rise we’re starting to experience,” he said.

“What we’re going to have to do is take a look at all of the old seawalls … and rebuild a lot of that over time.”

Click to play video: 'B.C. floods: Rebuilding highways with climate change in mind'

B.C. floods: Rebuilding highways with climate change in mind

B.C. floods: Rebuilding highways with climate change in mind – Nov 28, 2021

While building more resilient seawalls will be an engineering challenge, much of what sea level rise presents for cities is a planning challenge, Geller said, as flood construction levels — the minimum height habitable structures can be built at — slowly rise.

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“The biggest challenge is not to just be reactive,” he said.

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“These days we are too often dealing with trying to cure a problem that should have been prevented 20, 30, 40 years ago when we first started to talk about the potential impacts of climate change.”

Nearly a decade ago, the B.C. government laid out guidelines for coastal communities to help them adapt to the impacts of rising sea levels,.

The document proposes four strategies to deal with the effects, ranging from avoiding construction in potentially at-risk areas, to adapting infrastructure, to protecting at-risk structures to managed retreat in areas where the impacts can’t be effectively or affordably dealt with.

Some of those strategies are already being implemented.

In 2014, for example, the City of Vancouver amended its building bylaw to raise the flood construction level in flood hazard areas by one metre.

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In West Vancouver, where much of Ambleside Park was underwater during the storm, the Ferry Building Gallery escaped unscathed, after being raised during ongoing restoration work specifically to protect it from sea level rise.

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Legacy sea-side infrastructure like Vancouver’s seawall, however, could pose a bigger challenge in the years to come, and Clague said even with major upgrades we may need to be expect them to be routinely damaged.

“I don’t think we can abandon them, but we need to look at how we can better protect them,” he said.

“(They) may be a thing of the past — it’s a terrible thought, I hate to say it.”

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