It has long been understood that clearcutting forests leads to more runoff, worsening flooding. But a new study finds that logging can reshape watersheds in surprising ways, leading to dramatically more flooding in some forests, while having little effect on others.
The study looked at two watersheds in North Carolina’s Blue Ridge Mountains that had been logged in the late 1950s, one north-facing and one south-facing. In the north-facing watershed, which saw less sunlight and retained more moisture, floods hit up to 18 times more often for more than 40 years after clearcutting. The most extreme floods were more than twice as large as before logging. In the south-facing watershed, however, clearcutting had virtually no impact on flooding.
“This research challenges conventional thinking,” said lead author Younes Alila of the University of British Columbia. “We hope the industry and policymakers will take note of the findings, which show that it matters not only how much forest you remove but also where, how, and under what conditions.”
Researchers say their findings, published in the Journal of Hydrology, could help foresters elsewhere determine which areas would be most prone to flooding if logged, and could illuminate how the loss of woods may have worsened recent floods.
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