Metro Vancouver facing future threat from rising sea levels levels, future, before

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Metro Vancouver facing future threat from rising sea levels


METRO VANCOUVER - Rising sea levels could cause flooding in Metro Vancouver communities that never had to worry about it before, such as False Creek and Kitsilano, according to new projections from the B.C. government.

Most coastal communities in B.C. have bylaws that restrict construction in coastal areas prone to flooding.

Those restrictions are based on the water level at high tide, plus an extra allowance for surges and waves, which occur during major storms.

The problem is those calculations are based on current sea levels and don’t take into account what most experts now believe is inevitable: a rise in global sea levels of a metre or more by 2100.

“It would mean that structures that are safe now under current conditions ... may be getting wet in 2100,” said Neil Peters, the B.C. government’s inspector of dikes.

On Wednesday, the provincial government released new maps indicating which area of the province could be vulnerable to flooding in 2100.

Many of the areas highlighted on that map, such as wide swaths of Richmond and Delta, are below sea level and already have sophisticated dike systems in place.

But the map also highlights a number of areas not now prone to flooding, such as False Creek, parts of Kitsilano and a portion of North Vancouver near the Second Narrows bridge.

“Some of those areas could be impacted and they’re not currently recognized as floodplain areas,” said Peters. “There are no dikes there.”

Peters said Vancouver’s Southlands, which is now in a floodplain, will also see its flood risk increase as sea levels rise.

It’s up to each city to map its floodplain and draft bylaws that protect homeowners from floods.

To help with that task, the province on Wednesday also released a set of detailed guidelines for municipalities on how to construct floodplain maps that take into account a gradual rise in sea levels over the next century.

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Climate-change experts have predicted that, by 2100, sea levels could rise anywhere from half a metre to two metres.

Peters said the province assumed a rise of one metre in its calculations.

“It’s not an extreme estimate, by any means,” he said.

Once cities have revised their floodplain maps, said Peters, they have a few options on how to proceed.

Some may choose to build dikes, or raise existing dikes, to allow development to continue in areas that might otherwise be flooded.

Other cities might forbid new buildings in the floodplain and, over time, encourage the removal of those already there.

“It’s called managed retreat,” said Peters. “Over a number of building life cycles, you eventually abandon an area for a lower land use, like parks or fields, something that isn’t vulnerable to flooding.”

The good news, said Peter, is that communities have time to adjust to the new reality.

“This isn’t an imminent threat,” he said. “Sea-level rise is slow and we’ve got time to plan.”

Paul Henderson, director of strategic initiatives for the City of Vancouver, said city staff are already working on a long-term climate-change adaptation strategy, which it plans to present to council next year.

That strategy includes how to address the increased risk of flooding in places such as False Creek. One possible solution, he said, is to raise the height of existing seawalls.

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False Creek, taken on Friday, November 12, 2010. The area could be under water in the future, B.C. experts say.



Bike riders enjoy an area which, according to recent B.C. government calculations, could one day be under water.