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B.C. can limit flooding by reducing clear-cutting: UBC scientist

New paper shows link between clear-cutting and more flooding, including extreme floods

If the provincial government is serious about protecting downstream communities from flooding, it needs to protect upstream watersheds against clear-cutting, says the senior author of a new study.

The study by Younes Alila, forestry professor at the University of British Columbia, links clear-cutting with more flooding, including extreme floods.

The root causes of flooding lie in changes to run-off, Alila said, adding government officials cannot claim they are protecting downstream communities, unless they are developing appropriate policies related to land use, water use and forest management.

“(We) have been logging like hell in the headwaters everywhere in this province,” Alila said. “You just need to fly over British Columbia with an airplane…and if you actually throw your hat out of an airplane window, there is a 90 per cent chance it falls on a clear-cut.”

Alila made these comments after he and hydrologist Robbie Johnson had published a paper examining the relationship between flooding and clear-cutting, drawing on data from the Deadman River and Joe Ross Creek watersheds north of Kamloops.

“When only 21 per cent of trees in the watershed were harvested, using clear-cut logging, the average flood size increased by 38 per cent in the Deadman River and a staggering 84 per cent in Joe Ross Creek,” Johnson said.

Reduced forest cover leads to more snow on the ground and more sun reaching snowpack. With much less forest cover to catch and shade the snow, more of it melts faster, causing larger floods, Alila.

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Previous research had already linked the loss of forest cover to flooding, but this paper goes further by showing the cumulative effects of clear-cutting downstream and the link between the size and state of watersheds and flooding.

While companies must replant clear-cut areas, such measures alone won’t matter, Alila said. For about two decades, re-planted trees have no effect on run-off, he said. “It takes 60 to 80 years in the Interior for the impact caused by previous cutting to recover to pre-logging conditions,” he said.

The provincial government is currently reviewing forest management practices of timber supply areas. Alila sees this as an opportunity to change course away from the historical preference for clear-cutting toward more selective forms of logging.

The last three years of climate change have demonstrated how it is “extremely urgent” that government designs policies that appreciate nature-based solutions.

The provincial government is also currently working on a flood management strategy for the province. Alila said that if government wants to reduce the costs of disasters like the 2021 floods in the Fraser Valley, it needs to change the land use practices far upstream.

Past governments have left individual municipalities and regional districts in charge of preventing floods, he said. But they do not have the means to control the cause of flooding, changes in the land cover, he added.

“So therefore, we definitely need to work much harder on coordination and something like floods need to be centrally managed,” he said.

Alila is also the bearer of other bad news. The effects of wildfire on flood risk is “actually orders of magnitude bigger than the effects of conventional clear-cut logging,” he said.

Fire burns away organic matter, leaving behind soil that repels water, he said.

“Now…the slopes and the landscape are acting as parking lots,” he said. “(We) should brace ourselves for the worst when it comes to the next flood season.”

The Ministry of Forests acknowledged the changing climate, adding that is why scientists and forest professionals are constantly reviewing significant amounts of data when determining where and when to encourage sustainable harvesting.

The ministry said that it is always developing new silviculture methods and findings into forest practices as part of a commitment to developing and implementing alternatives to clear-cutting practices. Any research, including this new paper, is a welcome addition to an always changing field of study, it added.


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Wolf Depner

About the Author: Wolf Depner

I joined the national team with Black Press Media in 2023 from the Peninsula News Review, where I had reported on Vancouver Island's Saanich Peninsula since 2019.
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