Clear‑Cut Logging Can Dramatically Increase Flood Risk
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https://theconversation.com/new-study-finds-clear-cut-logging-can-dramatically-increase-flood-risk-284825 <-- shared technical media article
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https://doi.org/10.1016/j.foreco.2026.123895 <-- shared paper
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H/T @Daniel Pierce | Ramshackle Pictures
“Here is a clear and simple breakdown of some of the latest bombshell findings out of the UBC Hydrology Lab… using a probabilistic framework, known as attribution science in the climate world. [The researchers] studied two watersheds in BC’s Okanagan Valley near Summerland. In this area, they found that climate change was actually making the frequency of floods go down, but forest harvesting counteracted the effects of climate change and increased the flood risk by 10-fold (!!!) turning a 20-year flood into a flood that occurs every two years. [The H/T] truly want to know how the BC government and timber industry are responding to this new science internally. They’re absolutely silent on it in public as they continue business as usual…”
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“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. [The authors] recently published study [paper link above] 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.
[They] 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.
[They] 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 critical to making informed decisions that can mitigate risk, and lower costs passed on to the public…”
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“HIGHLIGHTS
Nonstationary frequency pairing isolates logging impacts from climate driven variation.
Climate, and logging driven changing probabilities of peak flows can be quantified.
Logging raises flood probabilities across all return periods.
South-facing mid-elevation cuts strongly amplify snowmelt-driven peak flows.
This updated method strengthens causal inference through an explicit counterfactual and a direct control–treatment comparison.
ABSTRACT: Stationary frequency pairing is one of two main methods used in paired watershed studies assessing forest harvesting impacts on peak flows. However, climate change, ongoing harvesting, and regrowth often lead to nonstationarity in peak flow distributions. We present a nonstationary frequency pairing approach that evaluates harvesting impacts by allowing the parameters of peak flow frequency distributions to vary through time in response to physically based covariates. Applied to a large snow-dominated paired watershed study (35 km2, and 43 km2) in British Columbia, Canada, the method reveals that all peak flow magnitudes are sensitive to harvesting, with flood frequency shifts intensifying as event magnitude increases. These findings reflect the extent and spatial distribution of cut blocks across the sensitive large-scale physiography seen at the treatment watershed. They also demonstrate the method’s power to isolate harvesting effects from climate-driven variation. Key advantages of the method include: (i) enabling novel understanding of how macro-scale physiography controls relationships between covariates and peak flow probability, and (ii) providing time-varying estimates of harvesting effects that reflect different stages of watershed disturbance and recovery, (iii) identifying the causal influence of climate drivers on changing flood risk, and disentangling these effects from those of forest harvesting. This study extends the nonstationary paired-watershed framework to a new snowmelt-dominated setting, demonstrating its capacity to uncover the role of macro scale physiography in governing the effect of harvesting on peak flows. In doing so, it advances the use of probabilistic causation in forest hydrology and provides a more rigorous basis for evaluating watershed disturbance…”
#Nonstationary #Probabilisticphysics #Foresthydrology #Floodfrequencyanalysis #Snowmelt #Causalinference #flood #flooding #forest #forestry #water #hydrology #OkanaganValley #watershed #BC #Canada #BritishCanada #clearcut #logging #harvesting #practices #climatechange #extremeweather #humanimpacts #caseexamples #floodrisk #risk #hazard #probabilistic #framework #attributionscience #policy #planning
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