Coastal flood risk in Lower Mainland will intensify in the future, says U.S.-based Climate Central

A new sea level data map shows flood risk zones will extend higher and further inland on Canada's coast, particularly impacting pop‐ ulated areas in parts of Metro Vancouver south of the Fraser River.

It's estimated 325,000 people in Canada will live on land falling in annual flood risk zones by 2100, according information released Thurs‐ day by Climate Central, a Princeton, New Jersey-based, non-profit group of scientists and communicators.

That's a 10 per cent in‐ crease from the group's 2030 estimate of 295,000 people facing annual flood risk.

Risk of significant coastal flooding is especially ap‐ parent in Richmond, Delta and South Surrey, said Peter

Girard, Climate Central's vice president.

By the end of the century, nearly all of Richmond in‐ cluding the airport, Delta and large chunks of Surrey will lie below annual flood levels, the new map projects.

"This isn't surprising," Gi‐ rard said during a zoom in‐ terview with CBC News.

"As you look south of Van‐ couver, you see areas already at risk of coastal flooding … and those risks increase over time and by the end of the century you're going to see significant risks."

Previous estimates from the Intergovernmental Panel on Climate Change project sea levels will increase to 0.5 metres by 2050 and one metre by 2021 along the B.C. coast, primarily affecting areas in the Lower Mainland like Richmond and Delta.

It's high time to prepare for the risks, Girard said.

"Being able to look 30 or 60 years into the future … means that planners in those areas can begin preparing for the risk before it becomes re‐ ality," he added.

Municipalities south of the Fraser River have been aware of the impending chal‐ lenge for a long time, Delta Mayor George Harvie said.

"We've been repairing [dikes] and looking at areas which are subjected to winds and storm surges and pro‐ tecting our residential areas," Harvie told CBC News.

But the Delta mayor said the responsibility of main‐ taining dikes is weighing heavy on local governments.

"We have about 67 kilo‐ metres of dikes in Delta and for us to bring them up to standard [can cost] $2 billion and that's just for Delta. It's not going to happen."

In 2011, the B.C. govern‐ ment transferred the respon‐ sibility of operating and maintaining dikes to the local government.

Harvie said he would like to see the province get more involved.

Climate experts say dikes aren't a silver bullet, and point to other protections municipalities can use.

According to Karen Ko‐ hfeld, director at SFU's School of Environmental Sci‐ ence, one such measure in‐ cludes wetland restoration.

"It's a classic example of some of the nature-based so‐ lutions that can be put in place to help protect the shoreline on a larger scale," she said.

The SFU professor said wetlands and marshes act as a defence system to reduce coastal energy by lowering the amplitude and speed of ocean waves, which mitigates storm damage and shields coastlines from erosion.

Delta Mayor Harvie said the city has partnered with the City of Surrey and Semi‐ ahmoo First Nation in a simi‐ lar marshland restoration project known as the Living Dike Pilot Project.

With the project at Bound‐ ary Bay, the largest salt marsh in southwestern Cana‐ da, collaborators aim to grad‐ ually deposit sediment into the marshlands over a 30year period. The plan aims to increase the marsh's height, forming a natural barrier ca‐ pable of withstanding rising sea levels.

What's causing sea lev‐ els to rise?

Kohfeld said one of the major contributors to sea lev‐ el rise is global warming.

The ocean is getting warmer, she explained.

"It's storing heat, and as the water warms up, it ex‐ pands. And that simple ex‐ pansion of sea water causes the volume of the ocean to get bigger."

Additionally, melting glaci‐ ers - large sheets of ice and snow - are adding more wa‐ ter to Earth's oceans, she said.

While an increase of 50 centimetres or one metre in sea levels over the course of the next 75 odd years might not sound as striking, experts caution against "underesti‐ mating the power of water."

Kohfeld said the increase in the amount of water will exacerbate the impact of king tides and storms.

Climate Central's Girard said the rise in global emis‐ sions is another contributor to elevated coastal flood risks.

"As long as we pollute, as long as carbon dioxide con‐ tinues to enter our atmos‐ phere, these impacts will be‐ come more severe," he said.