The Risks

Geographic Overview

Clackamas County is in northern Oregon and consists of two significant Level III ecoregions: Willamette Valley and Cascades. The Willamette Valley ecoregion in the western part of the county is more populated, is lower in elevation and has lower precipitation (37 to 60 inches) than the Cascades ecoregion, and is composed of fluvial terraces and floodplains, scattered hills, buttes, and adjacent foothills. The Cascades in the eastern part of the county is less populated, higher in elevation, and has higher precipitation (50 to 125 inches) and is dominated by coniferous forests that is managed for logging and recreational use. The union of the two ecoregions increases the diverse nature of the Clackamas County landscape and can have unexpected consequences related to wildfire in the highly populated areas in the western portion of the county.

Historically, forests regularly burned, reducing the amount of dry woody debris and, in turn, reducing the severity of wildfires. Modern land and forest management practices, pursuing a fire suppression strategy, resulted in the buildup of forest vegetation, such as woody materials from brush and downed trees and limbs. The buildup of forest vegetation increases the intensity and severity of fire risk. This is particularly true in dry forests where fire regimes were historically “high frequency, low severity” but due to fire suppression over the past 150+ years, fuels have built up. Conversely, in wet forests fire is uncommon with long intervals between fire events and when fires do occur, they tend to be severe, like the 2020 Labor Day fires. Fire suppression over the past 150+ years has had less of an impact on fuel build up in wet forests because they are naturally abundant in vegetation and are typically too wet to burn except during extreme weather events. For example, a natural fire rotation for the wet forests of Bull Run, which are extremely wet and productive, was determined to be 350 years and the fire regime is “low frequency, high severity”. Because fires are not common in forests west of the Cascades, less is known about the effectiveness of dry-forest fuel reduction strategies in wet west side forests. The Pacific Northwest Quantitative Wildfire Risk Assessment (QWRA) classifies these fuels as a fire risk for nearby communities. Household structures and communities adjacent to or incorporated on public lands have a higher risk of wildfire than households in more urban areas.

As development continues to expand into rural and wooded areas, the cost of fire suppression, risk mitigation, and disaster planning needs to be accounted for and planned. More people are moving into undeveloped areas, thus increasing their risk of wildfire displacement. The updated CWPP accounts for this increased risk and addresses policy recommendations that will support greater funding opportunities for these communities. As communities continue to develop in the high-risk areas of Clackamas County, the cost of fire management and community preparedness will disproportionally put pressure on households living near wildland areas. Therefore, the CWPP update recognizes an imperative need to increase interagency cooperation, promote effective communication between agencies, and create a fire resilient Clackamas County.

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