Oregon Department of Forestry
What do the colors on the map represent?
The map displays fire business threshold; low (green), medium (blue), high (yellow), very high (orange), and extremely high(red) indicating the potential for significant fires to occur. The map is one of many tools local ODF Fire Managers utilize when making decisions including changing fire danger restrictions, or forest closures.
How is a significant fire defined?
Equating significant fires with fire size has weaknesses. Regardless of size, the significance of a particular fire is dependent upon the fuels in which the fire burns. Fires burning in light fuels can burn large acreage in a short time, but can be controlled in a short time as well. Fuels (or fuel models) differ not only between parts of the state, but within individual units. Cost becomes the equalizing factor throughout the state, and represents the difficulty of suppression. Smaller acreage timber fires are much more significant than large acreage grass fires and that difference is reflected in fire costs. Discussion with ODF Fire Managers indicated a significant fire would be one that requires more resources than a unit currently funds and typically is represented by ODF costs that exceed $25,000.
Fire danger factors that increase exposure to significant fires can be established separately for each fire danger rating area (FDRA) analyzed. NFDRS indices and weather parameters are utilized where meaningful correlations exist and fire business thresholds can be established. Fire business thresholds are determined that result in having a relatively small number of days when a majority of significant fires occur. For example, on 25% of the days when a threshold is passed (ERC=70, for instance), 75% of the significant fires occur. These types of business thresholds have important implications for fire management decisions. There are several different fuel models used across the state and each FDRA has different threshold established based on historic climatology and fire history. In some cases it was necessary for an NFDRS indices and a weather parameter to be used. Two FDRA’s use ERC and Min RH to get the best correlation. Each analysis was conducted with local Fire Danger Technical Specialists to ensure the data being utilized was accurate and best reflected local conditions.
What is ERC?
Energy Release Component (ERC) is a number related to the available energy within the flaming front of a fire and is a good indicator of fire season severity and the potential for large and/or significant fires to occur. Fuel models represent the burning characteristics of different vegetation types. Fuel model G is often used because it comprises both fine and large dead fuels, as well as woody and herbaceous live fuels. Therefore, ERC in Fuel Model G is a good indicator of seasonal fire trends. However, local analysis should be conducted to determine what fuel model and index best correlate with historical fire occurrence.
What the Significant Fire Potential Map is not:
The Significant Fire Potential Map is not a adjective or Fire Danger map. The Fire Danger for each Unit or District is determined locally by Fire Managers is displayed on their individual website such as:
The Significant Fire Potential Map is not a regulated use or Industrial Fire Precaution Level Map.
The Forest Closure information is located at the following links:
More about the National Fire Danger Rating System (NFDRS) and ODF
NFDRS has a long history in the US and Canada. In 1954 there were eight different fire danger rating systems used throughout the country among various fire fighting agencies. Through agreements and compacts work on a national system was begun in 1959 and by 1961 an outline was established. In 1972 the system became operational nationwide. Until 1994 ODF was utilizing its own unique Fire Danger Rating System; after 1994 ODF transitioned to NFDRS. NFDRS is a relative system and is not intended to predict fire behavior but is intended to allow for a statistical analysis of historical fire and weather data to determine various percentiles in the distribution of historic data that will then serve as breakpoints for fire management decisions.
ODF Fire Environment Working Group
The ODF Fire Environment Working Group (FEWG) was established in 2005 with the purpose of providing information concerning fire intelligence and the fire environment for fire managers and firefighters around the State. This task was to be accomplished through training, guidance, and tool development in the areas of fire behavior, fire danger assessments, and fire planning. The tools developed are aids to safely, effectively, and efficiently accomplish fire management objectives. One of the focuses of the FEWG is to establish minimum baseline objectives related to understanding and implementing the National Fire Danger Rating System (NFDRS) and participation in fire planning opportunities such as Fire Danger Operating Plans. The goal is to move the department towards more effectively utilizing nationally recognized interagency tools and information that is currently available and that are being developed.
A series of Fire Danger Technical visits began in 2006 that brought members of the FEWG Steering Committee to locations across the state to provide peer review of pocket cards and the analysis used to produce those cards. A review of the method of communicating NFDRS indices to firefighters and mangers was reviewed and documented. The fire danger analysis which establishes fire business thresholds and is used to produce pocket cards is done locally, with a peer review by other fire danger technical specialists to ensure that the breakpoints have been developed in a valid and consistent manner across the state. A valid and consistent approach then makes this NFDRS analysis a useful tool that helps local managers make informed fire danger management decisions and also enhances fire fighter safety.
Additional fire business needs were identified that resulted in the ODF Significant Fire Potential analysis. Using FireFamily Plus software, historic fire occurrence and weather were analyzed in a consistent methodology . The Significant Fire Potential map became a by-product of the analysis. It provides a useful visual tool to make as assessment of the potential for significant fires across the state.