Latest news with #hydrology
Yahoo
3 days ago
- Climate
- Yahoo
Clearcutting tied to 18-fold increase in flood risk: UBC study
A new study from the University of British Columbia suggests that clearcut logging can make catastrophic floods up to 18 times more frequent. The study, published in the Journal of Hydrology, analyzed long-term data from one of the world's longest-running forest research sites in North Carolina, the Coweeta Hydrologic Laboratory. "We had a good opportunity to test out the effect of the physical characteristics of the landscape on the relationship between logging practices and flooding," Younes Alila, a UBC hydrologist and senior author of the study, told CBC News. Researchers compared two neighbouring watersheds, one facing north, the other south, that were both clear-cut in the late 1950s. They found that clear-cutting in the north-facing watershed, which receives less sunlight and retains more moisture, had a dramatic effect on flood behaviour."The north-facing watershed was super sensitive," Alila said. In that watershed, average flood sizes increased by nearly 50 per cent, while the largest floods were 105 per cent bigger than they were before logging. "Different sides of the mountains will respond differently to logging," Alila explained. He says the north side receives less sunlight, which keeps the soil wetter year-round. When storms arrive, the ground is already moist and can't absorb much water, causing more rain to run off into streams and rivers, resulting in larger floods. In contrast, the south-facing watershed, which loses more moisture due to greater sunlight exposure, saw almost no change in flooding after clear-cutting. WATCH | A clearcut the size of a city in B.C.'s Interior: Alila called the difference "a breakthrough finding," highlighting how landscape factors like the direction a slope faces can reshape a watershed's flood regime. "The point we are trying to make is that we can use the way Mother Nature designed the landscape … to better manage the forest in ways that minimize the risk to hydrology and the risk of floods." Precautionary approach In addition to slope orientation, the hydrology professor emphasized that other landscape characteristics, including whether the terrain is flat or mountainous, contains lakes, wetlands or floodplains, all influence how a watershed responds to logging. "You should not be logging in one part of a watershed without accounting for what's happening elsewhere in the same drainage basin," he said. "Water flows from highlands to lowlands so we need cumulative impact studies before moving ahead with forest development." Alila says the current regulations in B.C. don't require companies to conduct proper watershed-level impact assessments before logging. Researchers say the study's findings are directly relevant to the province, where clear-cut logging remains common and terrain features mirror those of the test site. "Clear-cut logging in B.C. has increased the downstream flood risk rather dramatically," Alila added. He points to the devastating 2018 floods in Grand Forks, B.C. as an example, saying clear-cutting in the Kettle River watershed played a major role. Most flood models that predict the behaviour of floodwaters, assume a simple, predictable relationship between logging and flooding, the UBC professor says. For example, cutting down X per cent of trees, will likely result in Y per cent more water runoff. But the study says after clear-cutting, the risk of extreme and unpredictable floods increases in ways that these basic models can't capture. "This experimental evidence validates our longstanding call for better analysis methods," said Alila. "When we apply proper probabilistic tools to long-term data, we find much stronger and more variable impacts than older models suggest." Jens Wieting, senior policy and science advisor with Sierra Club B.C., said the study underscores the need to reform forestry practices to respond to climate risks. "This study is really demonstrating that we need a precautionary approach," said Wieting. "Clear-cutting can make climate change impacts worse." He said moving away from clear-cutting and toward selective logging — a practice where only certain trees are harvested, leaving the rest of the forest intact — could help reduce flood risk, restore degraded landscapes, and save money in the long run by avoiding climate disaster costs. Province acknowledges research In a statement to CBC News, the B.C. Ministry of Forests said it "appreciates the research being done at UBC" and emphasized that the province continues to invest in water and forest management. "Currently, through allowable cut determinations, the Chief Forester places limits on the rate of cut in each watershed to help provide balance to the many values our forested landscapes provide, including reducing flood risks," the statement reads. The ministry says it's also moving beyond traditional modelling to better understand how changes to forests, water, and climate affect long-term sustainability. That includes promoting practices like selective thinning, fuel management and forest restoration. The province has also introduced Forest Landscape Planning (FLP), which it describes as one of the most effective tools for reducing flood risk at a broader scale. Still, Alila says implementation of old-growth deferrals and other reforms from the province have been slow. "We continue old-growth logging…we've been aggressively clearcut logging for the last many decades so we only have a bit left."
CBC
3 days ago
- Science
- CBC
Clearcutting tied to 18-fold increase in flood risk: UBC study
Social Sharing A new study from the University of British Columbia suggests that clearcut logging can make catastrophic floods up to 18 times more frequent. The study, published in the Journal of Hydrology, analyzed long-term data from one of the world's longest-running forest research sites in North Carolina, the Coweeta Hydrologic Laboratory. "We had a good opportunity to test out the effect of the physical characteristics of the landscape on the relationship between logging practices and flooding," Younes Alila, a UBC hydrologist and senior author of the study, told CBC News. Researchers compared two neighbouring watersheds, one facing north, the other south, that were both clear-cut in the late 1950s. They found that clear-cutting in the north-facing watershed, which receives less sunlight and retains more moisture, had a dramatic effect on flood behaviour. WATCH | What are the lasting effects of B.C.'s logging? What are the lasting effects of B.C.'s logging? 12 months ago "The north-facing watershed was super sensitive," Alila said. In that watershed, average flood sizes increased by nearly 50 per cent, while the largest floods were 105 per cent bigger than they were before logging. "Different sides of the mountains will respond differently to logging," Alila explained. He says the north side receives less sunlight, which keeps the soil wetter year-round. When storms arrive, the ground is already moist and can't absorb much water, causing more rain to run off into streams and rivers, resulting in larger floods. In contrast, the south-facing watershed, which loses more moisture due to greater sunlight exposure, saw almost no change in flooding after clear-cutting. Visit a clearcut the size of a city in B.C.'s Interior 3 years ago Mike Morris is the MLA for Prince George-Mackenzie, a portion of the province that has historically been highly forestry-dependant and heavily logged. He is also a trapper who sees first-hand the impact of that logging on local wildlife, and he wants the rest of the province to know what it looks like. Correction: A previous version of the story included an estimation of the clear cut area that referred to the larger region, not the specific clearcut. Alila called the difference "a breakthrough finding," highlighting how landscape factors like the direction a slope faces can reshape a watershed's flood regime. "The point we are trying to make is that we can use the way Mother Nature designed the landscape … to better manage the forest in ways that minimize the risk to hydrology and the risk of floods." Precautionary approach In addition to slope orientation, the hydrology professor emphasized that other landscape characteristics, including whether the terrain is flat or mountainous, contains lakes, wetlands or floodplains, all influence how a watershed responds to logging. "You should not be logging in one part of a watershed without accounting for what's happening elsewhere in the same drainage basin," he said. "Water flows from highlands to lowlands so we need cumulative impact studies before moving ahead with forest development." Alila says the current regulations in B.C. don't require companies to conduct proper watershed-level impact assessments before logging. Researchers say the study's findings are directly relevant to the province, where clear-cut logging remains common and terrain features mirror those of the test site. "Clear-cut logging in B.C. has increased the downstream flood risk rather dramatically," Alila added. He points to the devastating 2018 floods in Grand Forks, B.C. as an example, saying clear-cutting in the Kettle River watershed played a major role. Most flood models that predict the behaviour of floodwaters, assume a simple, predictable relationship between logging and flooding, the UBC professor says. For example, cutting down X per cent of trees, will likely result in Y per cent more water runoff. But the study says after clear-cutting, the risk of extreme and unpredictable floods increases in ways that these basic models can't capture. "This experimental evidence validates our longstanding call for better analysis methods," said Alila. "When we apply proper probabilistic tools to long-term data, we find much stronger and more variable impacts than older models suggest." Jens Wieting, senior policy and science advisor with Sierra Club B.C., said the study underscores the need to reform forestry practices to respond to climate risks. "This study is really demonstrating that we need a precautionary approach," said Wieting. "Clear-cutting can make climate change impacts worse." He said moving away from clear-cutting and toward selective logging — a practice where only certain trees are harvested, leaving the rest of the forest intact — could help reduce flood risk, restore degraded landscapes, and save money in the long run by avoiding climate disaster costs. Province acknowledges research In a statement to CBC News, the B.C. Ministry of Forests said it "appreciates the research being done at UBC" and emphasized that the province continues to invest in water and forest management. "Currently, through allowable cut determinations, the Chief Forester places limits on the rate of cut in each watershed to help provide balance to the many values our forested landscapes provide, including reducing flood risks," the statement reads. The ministry says it's also moving beyond traditional modelling to better understand how changes to forests, water, and climate affect long-term sustainability. That includes promoting practices like selective thinning, fuel management and forest restoration. The province has also introduced Forest Landscape Planning (FLP), which it describes as one of the most effective tools for reducing flood risk at a broader scale. Still, Alila says implementation of old-growth deferrals and other reforms from the province have been slow.
Bloomberg
23-07-2025
- Business
- Bloomberg
China Says It Spoke With Neighbors on Planned Mega-Dam's Impacts
China said it has talked with countries downstream about its new dam project in Tibet, a massive undertaking that will affect a key source of water for India and Bangladesh. 'China has carried out cooperation on hydrology reporting, flood prevention and disaster alleviation with relevant downstream countries and has had necessary communication with them,' said Chinese Foreign Ministry spokesman Guo Jiakun during a regular press conference on Wednesday.
Arab News
12-07-2025
- Science
- Arab News
What We Are Reading Today: ‘Following the Bend'
Author: ELLEN WOHL When we look at a river, either up close or while flying over a river valley, what are we really seeing? 'Following the Bend' takes readers on a majestic journey by water to find answers, along the way shedding light on the key concepts of modern river science, from hydrology and water chemistry to stream and wetland ecology. In this accessible and uniquely personal book, Ellen Wohl explains how to 'read' a river, blending the latest science with her own personal experiences as a geologist and naturalist who has worked on rivers for more than three decades.
ABC News
29-06-2025
- Climate
- ABC News
Flood awareness a high priority for Tasmanian BOM hydrologist Abrar Shabren after Fiji childhood horror
Abrar Shabren knows from firsthand experience the deadly dangers of floodwaters. "It was in our village when I was in year 6 that I saw my friend washed away by floodwaters when we were walking to school," Mr Shabren said. The devastation of seeing a childhood friend taken by floods in Fiji has led to the Hobart-based hydrologist working at the Bureau of Meteorology (BOM), communicating the risks associated with severe weather events to as many people as possible. Mr Shabren has worked in Fiji, and was "fortunate to be posted to Casey Station in Antarctica, [and to] Melbourne, Sydney and Brisbane". "But it was during a trip to Tasmania in 2023 that my wife and I went to Bruny Island, and she fell in love with the place," he said. "And here we are loving everything about the island state. "My studies have seen me become a meteorologist and a hydrologist. The senior hydrologist's first experience forecasting Tasmanian floods was in 2016 when floodwaters almost broke the Launceston levy. It reinforced to Mr Shabren the differences in flooding seen in the tropics and other parts of Australia in the summer months, compared to that seen predominantly in the colder Tasmanian seasons. "Riverine flooding in Tasmania varies significantly between winter and summer due to differences in weather patterns, rainfall distribution and catchment conditions," he said. From mid-autumn to early winter, continuous rainfall from these frontal systems, known as 'autumn rains', particularly affects the western, southern and northern parts of the state, making catchments wet and susceptible to rainfall runoffs. "The persistent rain saturates the soil, reducing its ability to absorb additional water, which increases the chance of higher stream flows and riverine flooding," Mr Shabren said. "Winter typically brings more frequent and higher rainfall, resulting in consistent riverine flooding with passing frontal systems." Mr Shabren said in higher altitudes, snowmelt can further raise river levels, exacerbating flood risks, such as in catchments like the Huon and Meander Valley. "The ground often remains saturated from continuous rain, causing prolonged flooding and higher water levels. Catchments in Tasmania can remain saturated into spring, increasing the chances of flooding associated with springtime weather systems such as low-pressure systems off the east coast. Mr Shabren said summer floods were less frequent but could occur suddenly due to intense, short-duration rainfall events, often catching communities by surprise. These events are usually associated with thunderstorms or weather systems fed by tropical moisture, which can dump large amounts of rain in a short period. "These floods are usually more localised, affecting specific areas rather than widespread regions," he said. The dry ground in summer can lead to rapid runoff, as the hardened soil is less able to absorb water, causing flash floods that rise and fall quickly. This can also lead to rapid rainfall runoffs and flash flooding as the catchment condition and flood behaviour changes. Mr Shabren said all seasons require continuous monitoring and preparedness. The BOM in Tasmania works closely with the State Emergency Service, state government agencies and councils in providing warning service and decision-making advice to the community, he said. "When all environmental conditions indicate potential riverine flooding, the Bureau of Meteorology issues a Flood Watch product, 1 to 4 days in advance. "Subsequently, flood warnings are then issued according to the flood service level specifications for Tasmania, which are available on the BOM website. A Flood Watch is issued when forecast rainfall suggests that local and/or riverine flooding is possible, but uncertainty remains about the exact location and intensity. It may cover large areas and refer to: Flood Watch areas may not be covered by formal flood warning services. A Flood Warning is issued when flooding is more certain, often after rain has begun. It is more targeted, covering specific catchments, and usually includes predicted flood severity. Find out more by visiting the Flood Knowledge Centre and stay up to date with the latest forecasts, observations and warnings by visiting the Bureau's website and by downloading the BOM Weather app
