Wetlands key to controlling rising sea levels, says study
As sea levels rise, building higher walls may not be the best way to protect property, infrastructure and ecosystems in southwestern B.C., according to the leader of a four-year project aimed at coordinating local adaptation efforts.
Low-lying wetlands, salt marshes and natural assets are not just valuable habitat for wildlife, they might also be potent tools to manage flooding as sea levels rise by up to one metre over the next 80 years, said Kees Lokman, director of the UBC Coastal Adaptation Lab.
The traditional approach to flood management has led to the construction of nearly 300 dikes stretching more than 1,000 kilometres around B.C., much of that concentrated in Metro Vancouver and the Fraser Valley.
Many of those dikes were built to a design standard set in the 1960s and some are up to one metre too short, according a provincial government study.
Only about four per cent of local dikes are up to standard and the bill to fix them would top $10 billion. Canada's federal disaster mitigation fund is currently just $2 billion.
But simply upgrading the dikes may not be the solution it appears to be.
“Dikes are very much geared to human safety and protecting assets, but we haven't done much to protect our ecosystems,” said Lokman. “We are learning that wetlands are not only important as habitat, they can also buffer storm surges.”
Built solutions can also be made to mimic natural assets.
For instance, living dikes that gently slope toward the sea provide protection for the built environment and enable plants and animals to take up residence and slowly migrate up as sea levels rise.
Conventional dikes built on river delta soils have a tendency to subside over time. The City of Surrey calculated adding one metre to their dikes would cause them to subside by about 50 centimetres, Lokman said.
“The project will increase the likelihood that Surrey and other jurisdictions will embark on other coastal nature-based solutions by better assessing the benefits of the project and increasing awareness of flood risk,” said Surrey project engineer Matt Osler.
Though the notion will be contentious, it could be more prudent to simply retreat from low-lying areas, buying out homeowners as their properties become uninhabitable.
“At some point your flood insurance is going to go up or even be unattainable,” he said. “Once that understanding starts to sink in people become much more comfortable with the idea that a strategic retreat isn't such a bad idea.”
A four-year, $1-million project funded by the Pacific Institute for Climate Solutions dubbed Living with Water will explore integrated flood responses applied on a regional scale.
“There's a whole range of solutions that we could be exploring, but we currently don't have the policy and regulatory tools to actually administer these projects,” he said.
Living with Water aims to bring governments together, while integrating Indigenous knowledge and the perspective of the Squamish and Tsleil-Waututh First Nations.