A UBC study finds that conserving just five per cent of watersheds and two per cent of Canada’s land could shield more than half of urban floodplains, safeguarding millions.
Researchers at the University of B.C. say there’s a nature-based way to protect cities from floods, like the 2021 catastrophic flooding in B.C. or more recently the deadly floods that wiped out towns in Spain.
Study author and UBC forestry expert Dr. Matthew Mitchell says this is the first of its kind research in Canada to explore how ecosystems function as natural flood buffers.
Key ecosystems safeguard 54 per cent of built-up areas and 74 per cent of cropland in floodplains, according to the study. When these areas are preserved, they absorb water, slow run-off and reduce the strain on flood defences,” said Mitchell.
“Trees and vegetation can capture that rainfall as it comes down. But also one of the major ways beyond that is the soil and having places where it’s not impervious, it’s not pavement or concrete,” he said in an interview.
“The soil really absorbs and slows it down. So when we get these atmospheric river events there’s a capacity to slow that down and release the water over a longer amount of time, rather than all at once.”
Mitchell said for many people conserving nature is about protecting biodiversity, and that’s true but in doing so governments also protect communities from floods.
While using infrastructure such as dams to protect watersheds near cropland is important, researchers say this should be done in tandem with nature conservation.
Some solutions include restoring riparian areas, or land that borders a body of water, such as a river, stream, lake, or wetland, and putting in hedgerows that can help slow the flow of water, said Mitchell.
Cities should be adding more green spaces and trying to reduce concrete surfaces. Communities can look at creating rain gardens, which are landscaped areas that collect and filter rainwater from a roof or street, allowing it to soak into the ground, he added.
“We must restoring and add vegetation where we can but of course this can be complicated because we can’t just say to farmers, ‘oh, you need to get rid of your crops here and plant trees.’ We need to give them an incentive for that or we need to figure out ways to make up for their loss,” he said.
“Maybe we look at places where it doesn’t make sense to farm. Can we add in different types of vegetation that might help with flooding?”
The study highlights key regions where conservation could have the greatest impact across Canada, including several key areas in B.C.
Researchers looked at places that can potentially store the most rainwater and precipitation, and where they are in relation to important downstream areas, where there are communities, crop lands, and important infrastructure.
Areas around the Lower Mainland, Vancouver Island and the Okanagan, especially Kelowna where there have been massive wildfires exposing mountainsides, are some key B. C.regions where researchers say more needs to be done to preserve the surrounding natural environment to prevent flooding.
Canada faces numerous challenges because of climate change, human alteration of rivers, watersheds and floodplains, the study notes.
With weather patterns shifting fast, projections call for more flooding across the country, which means governments must look at protecting natural ecosystems as part of its adaptation strategy, the study concludes.
Mitchell suggests planting more trees and vegetation on slopes around Metro Vancouver can help slow down rainfall so it doesn’t overflow the infrastructure.
“These natural ecosystems offer cost-efficient, low-maintenance, and resilient solutions that can complement the role of human-made infrastructure in flood prevention,” the study says.
With files from The Canadian Press