Burns from the Lionshead Fire. Image courtesy of the Incident Information System
On August 16, 2020, a lightning strike in Lionshead Canyon ignited what would come to be known as the Lionshead Fire. Three weeks later, a historic easterly wind event swept across the Northwest, stoking the flames. The resulting conflagration burned over 200,000 acres, destroyed more than 1,500 structures, including over 700 homes.
According to Kelly Gleason, the fires that ravaged the western Oregon Cascades last summer are exceedingly rare.
Gleason is an ecohydrologist and assistant professor in the Department of Environmental Science and Management at Portland State University. Gleason's research focuses on interactions between hydrology, climatology, and ecology under a changing climate. For the last decade, Gleason has studied the effects of forest fires on snow hydrology, including snow accumulation, melt, and the residual impacts on downstream water quality, quantity, and availability.
The Beachie, Lionshead, and Holiday Farm fires devastated communities in the western Cascades and torched extensive tracts on National Forest lands. In the immediate aftermath of the disaster, scientists like Gleason see the potential to learn how such fires affect the Cascade snowpacks critical to western Oregon's water resources.
Gleason recently received a Rapid Response Research (RAPID) grant from the National Science Foundation to study the immediate effects on watersheds in forests where fires rarely occur. Specifically, Gleason is interested in the snow-fed watershed at the Britenbush River's headwaters, where the Lionshead fire left the landscape a mosaic of burned and unburned forest lands. The watershed feeds the reservoir at Detroit Lake and is a critical water source for hundreds of thousands of people in the Willamette Valley.
Immediately following a burn, black carbon and burned woody debris from damaged trees and shrubs can reduce snow's reflectivity. As a result, snow absorbs more solar radiation, which causes it to melt more quickly, particularly in warmer, subalpine ecosystems, like the forests of the western Cascades. The loss of reflectivity advances the timing of snowmelt and reduces the volume of stored water in the snowpack that water resource managers rely on when determining how to manage water resources to assure availability during the summer dry months.
Meanwhile, the increased snowmelt rates mobilize sediment and nutrients which create water quality issues and dam regulatory concerns in watersheds following forest fires. By combining data collected on location, Gleason and the research team will create computer simulations modeling the fire's potential impacts on water quantity, quality, and availability--information critical to managing downstream water supplies.
"We're interested in getting a broad picture of the fire's immediate impact on the snowpack at various elevations across space and time, and how the snowpack changes relative to the severity of the burn," Gleason said.
In addition to studying how the fire will affect winter snowpack and water resources later in the year, Gleason's data will lay the groundwork for exploring what at first seems like a contradictory idea. Gleason and others hypothesize that patches of forest left bare by wildfire could in the future act as a buffer against snowpacks diminished by a warming climate.
According to Gleason, gaps in the forest canopy created by fires could, after some time, retain a more significant percentage of mountain snowpack. The idea is that once black-carbon-producing remnants of the fire are no longer present, the burned gaps could act as a sort of refrigerator, sheltering the snow from the ambient heat produced by the forest while providing shade to protect the snow from solar radiation. Gleason is planning future studies to test this hypothesis.
"In the long run, we're interested in how these gaps in the forest structure following a fire could optimize snow retention over the long run to mitigate the effects of climate change on hydrology," Gleason said. "If that turns out to be the case, it could have important implications for how we manage forest fires and our water resources in the Western US.”