LINKS
Fires and Floods: Future-proofing forestry against climate catastrophes
UBC Forestry,June 29, 2022 “..In his investigations, Younes also found that clear-cutting is indeed likely contributing to an increase in the frequency and severity of floods. Treed areas shade the ground, slowing snowpack melt when temperatures increase, he explains. Without treetops and root systems to absorb rain and slow snowmelt, cleared areas can act as water basins. On mountainsides, runoff has nowhere to go but down, spilling into and sometimes overwhelming low-lying areas. “Current research has found cases of 100-year floods becoming 25 times more frequent in watersheds of very flat topographies.”
Clear-cutting forests linked to 18-fold increase in frequency and size of floods
By University of British Columbia on phys.org, July 17, 2025 “Clear-cutting can make catastrophic floods 18 times more frequent with effects lasting more than 40 years, according to a new UBC study. In one watershed, these extreme floods also became more than twice as large, turning a once-in-70-years event into something that now happens every nine years.”This research challenges conventional thinking about forest management’s impact on flooding,” said senior author Dr. Younes Alila, a hydrologist in the UBC faculty of forestry. “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.” References this scientific paper: Stochastic framework reveals the controls of forest treatment – peakflow causal relations in rain environment, Henry C. Pham et al., 2025 in Journal of Hydrology Tip if the Hat to Norris W for this one
Floods, Fires, Forests. For Younes Alila, It All Connects
Alice Kassam for The Tyee Sep 8, 2025 “In November 2021, record-breaking precipitation fell across British Columbia over two days, unleashing floods and landslides on a scale the province wasn’t prepared for. Thousands were forced from their homes. Five people died when a slide swept across Highway 99. For Younes Alila, a University of British Columbia professor of forest hydrology — the science of how forest disturbances affect water flows — the disaster came as no surprise. For more than a decade, his research had shown how B.C.’s land management choices, especially the approval of large-scale forest clearcuts, can amplify floods and landslides. He published in peer-reviewed journals, warned officials and spoke to anyone willing to listen. Few did. …“I’m not asking to stop forestry. I’m asking for the management of the forest to be guided by the peer-reviewed science, in order to minimize the effects on the environment and on downstream communities. Continuing to do business as usual, especially in a changing climate, is causing havoc. The government needs to stop listening only to the industry and start catering to the public.”
When Fire Burns a Path for Flood
Zoë Yunker for The Tyee zJune 19, 2023. “Parker Cove’s duelling disasters are connected. Here’s what that means for BC…Wildfires, particularly severe ones, can transform the way water moves over and through a landscape. Above ground, a fire is considered most severe when trees are blackened, their needles and leaves are gone, and the forest’s understory is eliminated. In an unburned forest, those trees help moderate the amount of water on and in the ground. Without that plant buffer, sudden spikes in rainfall or snowmelt hit the ground faster. That effect is magnified by the burn level below, also known as a fire’s “soil burn severity.” When a fire burns hot, it changes the density and mineral composition of the soil below, creating a water-resistant layer on top. “At a certain level, sand turns to glass,” said UBC adjunct professor Peter Wood, who focuses on forestry and climate change. “It’s not quite like that. But it’s on that level of creating kind of an impermeable, hard-baked surface.” When that happens, water can’t seep into the soil like it usually does. “When those rains come, they’ve got a waterslide to go down,” said Wood. And those flood triggers are escalated further when a wildfire is located on a steep slope, and when the fire burns at high elevations that get lots of snow in the winter. When temperatures rise in the spring, the ample snow on the ground melts fast and heads downhill.”
Why we see floods following fires: A tale of two extremes
The Weather Nework, July 6, 2023 “…Wildfires can alter landscapes in a few ways; they remove vegetation that would otherwise provide stabilization and absorption to the ground, and they can alter the soil composition itself. If a fire burns hot enough, or is persistent enough, it can change some compounds in the soil to make the soil hydrophobic. Meaning any heavy rainfall that occurs in the affected area will simply pool on the ground surface, as the soil will repel the water.”
Forests and Floods: Natural Infrastructure for a Green Recovery
Community Forests International:
Dani Miller, Megan de Graaf (MScF), Daimen Hardie for Community Forests International, April 2021 “INVESTING IN FOREST INFRASTRUCTURE ADAPTATION…Since 2018, Community Forests International has been developing one such initiative, specifically targeting Canada’s flood-prone Maritime Provinces: The Forest Infrastructure Adaptation (FORA) Project. The FORA Project aims to formalize the valuation, restoration, and financing of natural Acadian forest infrastructure for flood attenuation in New Brunswick. The aspiration of this pilot project is to create an investment-ready business case for mobilizing forest infrastructure solutions at scale and in similarly impacted regions throughout the Maritime provinces.”
Impact of Thinning and Contour-Felled Logs on Overland Flow, Soil Erosion, and Litter Erosion in a Monoculture Japanese Cypress Forest Plantation
Moein Farahnak et al., 2024. “This study investigated the impact of thinning and felled logs (random- and contour-felled logs) on overland flow, soil erosion, and litter erosion in a Japanese cypress forest plantation (2400 tree ha−1) with low ground cover, from 2018 to 2023 in central Japan…Overland flow increased in the plot with random-felled logs during the first year post-thinning (from 139.1 to 422.0 L m−1), while it remained stable in the plot with contour-felled logs (from 341.8 to 337.1 L m−1)… thinning with contour-felled logs can be considered a viable method for mitigating overland flow in monoculture plantations with low ground cover.”
Heavy Rain and Upland Forest
by Alexandra Kosiba for Northern Woodlands Magazine. Dec 1, 2024 “One of the most significant climatic changes that we’ve experienced in the Northeast is an increase in the frequency and intensity of rainstorms. With these downpours comes a heightened risk of destructive floods, especially in hilly and mountainous areas, where runoff moves swiftly downslope, washing out roads, inundating farm fields, and damaging buildings…”She offers practical techniques for reducing impacts of severe storms.
Threats to fish and fish habitat in the watersheds of Nova Scotia
Webpage under Fisheries & Oceans Canada. It provides a useful 0verview of fish and fish habitat in Nova Scotia, e.g. maps of
– Primary watersheds of Nova Scotia
– Distribution by watershed of both species listed under the Species at Risk Act and those assessed as “at risk” by the Committee on the Status of Endangered Wildlife in Canada
– Land cover disturbance by watershed across Nova Scotia
Referenced.
NCC Freshwater Conservation Blueprint
“This gallery showcases the Nature Conservancy of Canada’s (NCC) Freshwater Conservation Blueprint for the Northern Appalachian–Acadian Region of Canada.”
NCC Watershed Health Assessment
“This dataset contains the Watershed Health Assessment (WHA) for the Northern Appalachian–Acadian Region of Canada (New Brunswick, Nova Scotia, Prince Edward Island, and eastern Quebec).”
Beneficial Management for Riparian Zone in Atlantic Canada
No Date. From meta data: Created 2006-08-21, modified 2010-03-16. 52 pages Summarizes regulations etc
An Ecological Approach to Riparian-Buffer Definition, and Implications for Timber Harvests in Nova Scotia, Canada
Stoffyn-Egli, Patricia’ and Duinker, Peter. 2013. In Journal of Sustainable Development
Modeling Reforestation’s Role in Climate-Proofing Watersheds from Flooding and Soil Erosion
Robert L. France et al., 2019 in American Journal of Climate Change Abstract: The mitigation potential of reforestation for offsetting the deleterious effects of increased flooding and soil erosion projected to occur in Atlantic Canada through future climate change was investigated. Modelling determined a strong but non-linear relationship between extent of vegetative cover and runoff volume and discharge rate for a Nova Scotian watershed, suggesting that reforestation will reduce, but not completely prevent, flooding. Predicted erosion rates were found to be progressively reduced in relation to the extent of upland reforestation. Of three scenarios examined in which 60%, 65%, and 85% of the entire watershed are randomly reforested, only the latter would reduce the elevated erosion expected to occur through climate change back to present-day existing levels. Additional modelling revealed that comparable mitigation of soil erosion can ensue through implementation of 70 m streamside buffer strips, which would only take up 19% of the total surface area. Prioritizing riparian zones for reforestation will therefore subsume less of the overall productive land area and therefore enact a less severe socio-economic impact on agriculture and forestry.
Is extensive clearcutting in Nova Scotia causing excessive flooding 16Mar2022?
Post on nsforestnotes.ca on March 16, 2022
Forest Degradation Increases Community Vulnerability to Extreme Floods
Rachel Plotkin & Julee Boan on davidsuzuki.org May 14, 2024 “Forests, particularly older, more complex forest ecosystems, act as natural “managers” of rainwater and snowmelt, helping to slow the pace of water movement and reduce the risk of extreme flooding events. Their leaves and needles help to decrease the intensity of water hitting the ground. Older trees also usually have larger canopies, which disperse rainfall. Conifer trees, specifically, provide shade during the spring before the rest of the forest “greens up”, which helps to moderate the rate of snowmelt. Older trees and complex forest ecosystems also provide greater soil stability, as tree root networks and other plants provide expansive anchors and absorb water. Even when old trees in a forest eventually die, and no longer mitigate against flooding, they still serve a host of other values.”
A global synthesis on the effects of thinning on hydrological processes: Implications for forest management
Antonio D. del Campo et al., 2022. In Forest Ecology and Management. “…Thinning intensity of about 50% of the stand density is determined as the threshold at or over which hydrological processes are significantly affected. The duration of thinning effect can be set between 2.6 and 4.3 (throughfall) and 3.1–8.6 years (soil moisture and transpiration).”
www.forestresearch.gov.uk: Flooding
“Many parts of the UK are seriously impacted by flooding and the frequency of floods is expected to increase due to climate change…Care in species choice, soil management and drainage, woodland design, placement and management can mitigate these effects. They can also help to secure woodland benefits for reducing downstream flood risk.”
Forest fire, thinning, and flood in wildland-urban interface: UAV and lidar-based estimate of natural disaster impacts
Temuulen Ts. Sankey et al., 2024.In Landscape Ecology. “Wildland-urban interface (WUI) areas are facing increased forest fire risks and extreme precipitation events due to climate change, which can lead to post-fire flood events. The city of Flagstaff in northern Arizona, USA experienced WUI forest thinning, fire, and record rainfall events, which collectively contributed to large floods and damages to the urban neighborhoods and city infrastructure.”
Watershed Maps produced by ERTH5600
(Graduate Student class in the Department of Earth Sciences, Dalhousie University)
– Part 1 of 4: Average Slope of Watersheds: In Map Viewer
This map is one of four for a watershed characterization study. This dataset showcases the average slope of the watersheds for the tertiary and sub-tertiary watersheds associated with Nova Scotia.
Description: This map was created for a watershed characterization study associated with ERTH5600 out of Dalhousie University. The choropleth map showcases 5 classifications of average watershed slope for each watershed. The watershed data was provided by the Government of Nova Scotia (Open Data Nova Scotia, 2021). The slope was determined from the Nova Scotia Digital Elevation map (Government of Nova Scotia, 2006).
– Part 2 of 4: Percentage Forest Cover for Watersheds: In Map Viewer
This map is one of four for a watershed characterization study. This dataset showcases the percentage forest cover of the watersheds for the tertiary and sub-tertiary watersheds associated with Nova Scotia.
Description: This map was created for a watershed characterization study associated with ERTH5600 out of Dalhousie University. The choropleth map showcases 5 classifications of percentage forest cover for each watershed tertiary and sub-tertiary watershed. The watershed data was provided by the Government of Nova Scotia (Open Data Nova Scotia, 2021). The forest cover data was also provided by the Government of Nova Scotia (2021). Item created: Apr 28, 2023
– Part 3 of 4: Drainage Density for Watersheds: In Map Viewer
This map is one of four for a watershed characterization study. This dataset showcases the drainage density for the tertiary and sub-tertiary watersheds associated with Nova Scotia.
Description: This map was created for a watershed characterization study associated with ERTH5600 out of Dalhousie University. The choropleth map showcases 5 classifications of drainage density for each tertiary and sub-tertiary watershed within Nova Scotia. The watershed data was provided by the Government of Nova Scotia (Open Data Nova Scotia, 2021). The water features data was also provided by the Government of Nova Scotia (Open Data Nova Scotia, 2022). The river data was extracted from the water feature layer to determine the drainage density for each watershed.
– Part 4 of 4: Percentage Lake Cover for Watersheds: In Map Viewer
This map is one of four for a watershed characterization study. This dataset showcases the percentage lake cover for the tertiary and sub-tertiary watersheds associated with Nova Scotia.
Description: This map was created for a watershed characterization study associated with ERTH5600 out of Dalhousie University. The choropleth map showcases 5 classifications of percentage lake cover for each tertiary and sub-tertiary watershed within Nova Scotia. The watershed data was provided by the Government of Nova Scotia (Open Data Nova Scotia, 2021). The water features data was also provided by the Government of Nova Scotia (Open Data Nova Scotia, 2022). The lake data was extracted from the water feature layer to determine the percentage lake cover for each watershed.
– Clustered Watersheds: In Map Viewer
This map presented watershed clusters based on watershed characterization parameters. The parameters utilized in clustering were drainage density, average watershed slope, percentage forest cover, and percentage lake cover.
Description: This map was created for a watershed characterization study associated with ERTH5600 out of Dalhousie University. The choropleth map showcases 5 classifications with respect to different clusters based on a k-means clustering algorithm. The four parameters utilized in clustering were drainage density, average watershed slope, percentage forest cover, and percentage lake cover.