In the past 30 years, floods have affected more than 2.8 billion people worldwide and caused over 500,000 deaths. In Canada, flooding has caused significant damage and disruption to communities across the country. The 2021 floods in British Columbia’s Fraser Valley cost an estimated $14 billion in damages.

Human activity that changes landscapes can make floods larger and more frequent. Our recently published study shows that clear-cut logging can dramatically increase flood risk, turning what was once a 50-year event into a flood recurring every three years, with the largest and rarest floods showing the greatest sensitivity to forest disturbance.

We studied a watershed on the west shore of Lake Okanagan near Summerland, British Columbia. Around 40 per cent of the site experienced logging. This watershed is no exception, as B.C.’s landscape has become dominated by clear-cut logging.

We found that, without logging, flood risk due to reduced snow melt was decreasing. But after logging, this was reversed, leading to significant upward trend in flood risk.

Flooding has become more frequent across B.C., leading to exorbitant costs to taxpayers. In order to address these challenges, it is critical that the drivers affecting flood risk are clearly understood.

Understanding the relationship between human actions across the landscape and their associated risks is........

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