About Oregon Wildfire Risk
Wildfire is a common and widespread natural hazard in Oregon.
Wildfire is a natural ecological process, but decades of fire suppression along with changes in land use and climate have increased wildfire risk in many areas. Over 41 million acres in Oregon are susceptible. The state experiences large wildfires most years that threaten homes and a range of wildland values.
Wildfires in Oregon can occur during any time of year, but nearly all burn between July and October. No area within the state is completely free from wildfire. Fires ignited by lightning or humans are common in the dry forests and grasslands of central, southwestern and northeastern Oregon.
These wildfire-prone areas support most of the state’s fastest growing communities.
What is wildfire risk?
The Society for Risk Analysis defines risk as "the potential for realization of unwanted, adverse consequences to human life, health, property or the environment." In other words, risk is the exposure to the chance of loss of something we value.
Wildfire risk is the potential for a wildfire to adversely affect things that humans value- lives, homes, or ecological functions and attributes.
Wildfire risk in a particular area is a combination of
Human activities, weather patterns, wildfire fuels, values potentially threatened by fire, and the availability (or lack) of resources to suppress a fire all contribute to wildfire risk.
The Wildland-Urban Interface
Zones where homes and other structures meet wildlands are termed the wildland-urban interface (WUI).
The amount of WUI in Oregon has grown rapidly. Fast-growing communities continue to expand into wildland areas, and the number of Oregon homes and businesses in the path of potential wildfires continues to escalate. Adjacent recreation and scenic areas, wildlife habitat and community watersheds may also be at risk.
Other states in the region face similar challenges. Many western communities are dealing with rising population in WUI zones, forest health issues and increasing frequency of destructive wildfires.
With an expanding range of human values at risk, wildfire has become major issue.
Oregon Communities at Risk for Wildfire
In 2005, Oregon completed its initial statewide Communities at Risk Assessment and list, which assigns each Oregon community a low, moderate, or high risk rating for:
Risk: The likelihood of a wildfire occurring. Based on federal and state data for historic wildfire occurrence.
Hazard: Resistance to control once a wildfire starts. Based on weather, topography and fuel that adversely affects suppression efforts.
Protection Capability: Adequacy of wildfire protection capabilities, including capacity and resources to undertake fire prevention measures.
Value: Human and economic values associated with communities or landscapes. A combination of human life values (50%), municipal watersheds (30%), and commercial forest values (20%).
Overall: A composite rating incorporating all of the factors listed above.
These wildfire risk ratings will help set large-scale fuel reduction priorities across watersheds and multi-county coordination areas.
Most counties in Oregon have completed their initial Community Wildfire Protection Plans (CWPPs) that:
- define community boundaries and WUI areas
- describe local wildfire hazards and values at risk
- explain how the community will reduce risk and respond in the event of a wildfire.
Some CWPPs rely primarily on the state-level risk assessment, but ideally they should incorporate more detailed local information and many already do so. Nearly all could benefit from more precise information about factors that contribute to wildfire risk and community readiness.
The Oregon Communities at Risk assessment and local CWPPs complement each other but differ in scale. Both efforts continue to be improved and refined. The 16 Geographic Information System (GIS) data layers used for Oregon Communities at Risk assessment were the best available that could be applied consistently statewide.
Communities are being encouraged to develop more robust local wildfire risk information and incorporate state-level GIS-based reporting methods.
Some important local values such as infrastructure, ecological values, and historical and cultural sites are not considered in the statewide assessment because consistent data was not available. These values should be addressed in finer-scale local CWPPs.
Toward these goals, state wildfire planners have prioritized needs for data that will strengthen community level plans and will also improve the precision of state level assessments. These information needs are listed BELOW.
Keeping current with risk assessment
Wildfire risk factors are complex and dynamic. Filling data gaps and keeping databases current are major challenges, so refining the Oregon Communities at Risk assessment and local CWPPs will involve sustained efforts at many levels.
Managers must often proceed with wildfire planning in the absence of perfect knowledge, but with increased attention on wildfire, newer and better information is becoming available.
For example, LANDFIRE vegetation data will soon be incorporated into the “hazard” section of the statewide assessment. At the same time, many local groups are working to improve existing CWPPs. These efforts are designed as “living” documents to accommodate this new knowledge.
Acquiring new data and sharing information products among community, state and federal-level wildfire planners are the keys to keeping wildfire risk assessments valid. Communities are encouraged to revisit and update their CWPPs after any wildfire that could change hazard mitigation priorities and strategies.
The Wildfire Risk Explorer facilitates these efforts by providing an information clearinghouse where citizens and communities, and wildfire agencies and planners can share and improve knowledge about wildfire risk in Oregon.
What kinds of local community information would improve the statewide assessment the most? Many kinds of information can improve the statewide risk assessment!
For each of the following information categories, state information needs are listed in priority order:
Information Category: Density of homes/population
- GIS point or structure outline of dwellings or businesses (not outbuildings)
- GIS centroids of “improved” tax lots
- Determined by local knowledge
Information Category: Community or Jurisdiction Name
Jurisdictional names used in the Communities At Risk Assessment may be different from the name in a signed CWPP or common name used by a local government.
When community name or names in a signed CWPP don’t align with the state list, please provide clarification.
Information Category: Community Boundaries
The statewide assessment lacks good information concerning local CWPP boundaries.
- Community boundaries based upon a signed CWPP
- Corrected jurisdictional boundaries
- Jurisdictions subdivided based upon the community at risk definition
Information Category: Wildland-Urban Interface Boundaries
- GIS layer of WUI boundary from a signed CWPP
- WUI boundary determined by a wildland fire protection agency using local knowledge of fuels, prevailing winds, historic burn patterns, and areas where strategic fuel break opportunities need to be considered.
Information Category: Fire locations, occurrence, risk
- GIS layer of fire district wildfire occurrence not reported by ODF or a federal agency.
- Fire locations or GIS density grid of non-ODF, non-federal jurisdiction derived from documented data (911 records) using the process described in the GIS metadata.
- A map covering non-ODF, non-federal jurisdiction with areas of low, moderate, and high wildfire risk delineated based upon local knowledge.
Information Category: Hazardous fuels
The vegetation and related fire-potential data used to determine fire characteristics are inferred from 1992-1996 satellite imagery. To compensate for the age of this data, burn severity data from recent large fires was used to update the vegetation data.
The process used to update the fuels data was developed through expert opinion and applies by ecoregion around the state. Assumptions were made about the flammability of nonforest vegetation (hay/pasture, etc) based on geographic region in the state. Data have not been field verified in many locations.
The fuels layer in the Oregon Statewide Communities at Risk Assessment will be updated with LANDFIRE data when it becomes available. HOWEVER, local review of the cross-walk assumptions used to generate a fuel model layer is still of value, especially for non-forest vegetation types.
Information Category: Fire Protection
- Validate and provide a GIS update of protection capability using the best local knowledge available, i.e. 911 response times, road access for fire equipment, etc.
Assign a “1” (LOW Risk) to areas where effective and consistent structural fire response occurs within 10 minutes- generally where full-time or moderate to high capacity volunteer departments can access fires within 10 minutes.
Assign a “2” (MEDIUM Risk) to areas where there is wildland response, but structural response within 10 minutes is limited and/or does not exist.
Assign a “3” (HIGH Risk) to areas with no organized response.
- Provide a written description of the above rating based upon a known geographic boundary (i.e. fire district).
Information Category: Municipal Watersheds
- GIS layer of watersheds meeting the Healthy Forest Restoration Act (HFRA) municipal watershed definition AND name of municipality AND number (population) of users if known.
- A map of watersheds meeting the HFRA municipal watershed definition AND number (population) of users if known.