College of Forestry

Oregon State University researchers are working with the nation’s leading fire modeling and local subject matter experts to develop the Oregon Statewide Wildfire Hazard Map. The purpose of the map is to identify where wildfires pose the most hazard to structures and other human developments. Similar methods are being used across the nation to support strategic wildfire risk reduction programs. As a science-based tool, the wildfire hazard map and related data will help state agencies and individuals objectively prioritize risk mitigation actions in Oregon communities.

How Are Burn Probability and Fire Intensity Modeled? 

To model burn probability, data related to these criteria are combined with information about historical fire events in spatial fire models. Then, fire models run 10,000+ simulations of plausible fire seasons to capture the full range of possible fire activity, under everything from mild to severe fire weather. 

Fire intensity is modeled using similar simulations that represent over 200 unique fire weather scenarios based on observed weather records. The fire intensity simulations capture the nuanced ways in which wind is affected by the landscape and the important changes in fire behavior as a result.   

Hazard Classifications

Scientists will use data from the wildfire hazard models to assign a hazard classification to every property in Oregon. Data values are calculated at very fine scales and then averaged across each tax lot. Each lot will then be assigned to one of three hazard zones: low, moderate or high.

Many factors contribute to a property’s hazard zone classification. Some of those factors are visible just by looking at a property – for instance, the amount and type of vegetation which primarily affect fire intensity. Other factors can’t be determined by looks alone. For instance, it is impossible to see the likelihood of experiencing a fire or the effect that regional climate patterns may have on a location’s burn probability.

The wildland-urban interface (WUI) is the geographic area where structures and other human development meet or intermingle with forests, rangelands and other vegetation.

Although wildfire disasters happen across a broad range of communities from rural to urban, research shows that most community wildfire disasters in the U.S. have occurred in the WUI. In some communities, the WUI is a transition zone between the more urban core and the wildlands. In these cases, structures in the WUI are threatened by fires spreading into communities, often via ember showers. In other areas, the WUI includes development intermixed with wildland vegetation such that communities are more directly exposed to flames when fires occur. In both cases, the WUI captures areas where there is enough wildland vegetation to support a wildfire AND enough development to result in significant damage to homes, critical infrastructure and human lives.

Image

Researchers at OSU mapped the WUI by applying the best available science and data to a set of definitions and rules developed by a diverse committee of stakeholders. First, in order to be in the WUI, there must be at least one structure per forty acres. Importantly, the rules also make some accommodations. For example, a collection of buildings (e.g., barns and garages) on a single property cannot constitute their own WUI just because there are enough buildings. Second, for areas that do have one structure per forty acres to be included in the WUI, they must also be surrounded by flammable vegetation or located within 1.5 miles of a large patch of flammable vegetation.

The WUI can be mapped in different ways. In Oregon, there are legal criteria for defining the WUI. To map the WUI for the statewide wildfire hazard map, OSU scientists applied the best available science and WUI definitions in OAR 629-044-1011. 

In accordance with Oregon law, the statewide hazard map and the WUI map are designed to be used together to help state agencies prioritize the communities with the highest need for hazard mitigation. To do that, agencies will use both maps to identify properties that are in the WUI and classified as high hazard. This will allow them to allocate state and federal funds to the areas with most need and determine where defensible space and/or fire hardening codes might apply.

Only properties meeting both criteria are potentially subject to defensible space and fire hardening rules required by state law. Fire hardening rules will not apply to existing structures unless significant home updates occur. The codes for both defensible space and fire hardening are currently in draft form and are not adopted for enforcement.

The maps will also help agencies, communities and individuals across Oregon better understand their hazard and prepare for future wildfires. The data and maps will be shared publicly on the Oregon Explorer.

The statewide wildfire hazard map will be publicly available on the Oregon Explorer, which serves as an interactive educational tool for Oregonians. Since 2007, the Oregon Explorer, a program of the Institute of Natural Resources at OSU, has been a public source of geospatial data and wildfire risk information used in state, regional and local risk management applications. 

Following a series of Rules Advisory Committee meetings (spring 2024), public outreach events to discuss the mapping process and related wildfire programs (summer 2024) and subsequent updates to the wildfire hazard map (2024), notifications will be mailed to property owners who are within both the high hazard category and the wildland-urban interface (WUI). 

In addition to supporting state agencies, the data and maps are publicly available on the Oregon Explorer for property owners and communities to learn about and plan for their wildfire hazard. If property owners believe that their wildfire hazard has been mischaracterized, they can appeal the decision through the Oregon Department of Forestry. 

Questions? 

Do you have other questions about the maps developed by OSU? Email us at osuwildfirerisk@oregonstate.edu.