King Fire burn severity - A look at potential impacts to water resources
The U.S. Forest Service has recently made data available on the burn severity of the King Fire. According to this new data, almost half of the trees and plants on the King Fire landscape burned at high severity. This means that little to no vegetation survived in those areas, leaving the soils exposed and at risk for erosion. t that we have created using the Forest Service’s data, a large portion of the high-severity burn occurred along the slopes of the Rubicon River – a tributary to the American River and contributor to Placer County Water Agency’s water supply.
In addition to vegetation burn severity, the Forest Service has released the soil burn severity map for the King Fire. This map shows that a significant amount of soil burned at high severity along the slopes of the Rubicon River. When soils burn at high severity, they tend to repel water rather than absorb and filter it. The result can be an increase in landslides, sedimentation, and more flash flood-like behavior in the watershed. These types of events can have serious impacts on water agencies’ and hydropower facility operators’ ability to manage their water and power delivery systems.
Between 1984 and 2010, there was a significant increase in the number of acres within a forest fire burning at high intensity, from an average of 20% in the mid-1980s to over 30% by 2010. The Rim Fire burned at nearly 40% high intensity, and as shown by the King Fire, the trend continues. Increasing forest restoration efforts in the Sierra Nevada to reduce wildfire severity is of critical importance to California’s water supply. These catastrophic fires have a direct effect on both the natural and built systems that millions of Californians rely on for water. For more information on how megafires in the Sierra directly impact California’s water supply and how stopping that trend can benefit our economy, check out our latest report - The State of the Sierra Nevada’s Forests.
Additional links to data and definitions:
- Vegetation burn severity data was provided by the U.S. Forest Service's Rapid Assessment of Vegetation Condition after Wildfire (RAVG) process.
- To learn more about how burn severity is measured, check out the U.S. Geological Survey's Composite Burn Index (CBI) Photo Series.
- To learn more about the difference between fire intensity effects on vegetation and fire severity effects on soil, check out this fact sheet created by the King Fire Post-Burned Area Emergency Response Assessment (BAER) Team.
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