Title:
Relative Risk to Communities from Wildland Fire of Idaho
Abstract:
For this analysis, it was assumed that a relative measure of the risks to communities from wildland fire could be characterized by integrating relative wildland fire risk, relative wildland fire hazard, and wildland urban interface. That is, within the wildland urban interface, risks are directly associated with the probability that an area will burn, as well as the likely fire behavior that would occur if that area did in fact burn. It was assumed that burn probability and likely fire behavior would contribute equally to the risks to communities. Agriculture, rock, urban, and water were not assigned a burn probability or relative fire behavior. Consequently, by definition, communities within these cover classes would not be at risk from wildland fires. For those communities occurring within burnable areas, a community’s risk to wildland fire could be characterized as follows:
CAR = (WUI + Relative WildlandFireRiskstd + Relative WildlandFireHazardstd)/3
Using the three components mentioned above, RelFireRiskCommunities_ID_BLM, "Relative Risk to Communities from Wildland Fire in Idaho" was derived.
Supplemental information:
Intermediate ArcInfo GRIDs CAR1026 and CAR10265cl were used in deriving RelFireRiskCommunities_ID_BLM shapefile. Values for CAR1026 were classified into five relative classes (low to high) using the natural break algorithm in ArcMap, to produce CAR10265cl. CAR10265cl was then summarized to a sub-watershed level(HUC6) by using an area-weighted average of the five relative classes where each class had a relative weight of 1through 5 respectively.
Those sub-watersheds having a value for communities at risk were then classified into five classes using the natural break algorithm of ArcMap. Those watersheds having no value for communities at risk were assigned a value of very low.
It is recognized that the factors used in this analysis to determine CAR are not the only factors that contribute to a community’s risk. Perhaps the most important variable relating to CAR is the capability of a community to respond to and suppress wildland fires. For example, how many suppression engines and crews are available and within close proximity of a community? In addition, access for engines and crews, slope steepness, and density (e.g., penetrability) of vegetation are other important factors relating to the success of fire suppression activities. In the future, suppression capability could be added to this risk assessment. However, factors involved with suppression efficiency may be too detailed and variable in nature to be accounted for in a mid-scale risk assessment.
RelFireRiskCommunities_ID_BLM(Relative Risk to Communities from Wildland Fire in Idaho).
Values for CAR (car1026 -ArcInfo Grid) at 90-meters were classified into 5 relative classes (low to high) using the natural break algorithm in ArcMap (car10265cl). These data were then summarized to a subwatershed level (HUC6) by using an area-weighted average of the 5 relative classes where each class had a relative weight of 1 through 5, respectively. This process was accomplished by using Multi-Resolution Integration Tool(MRIT), an ArcMap extension.
Those subwatersheds having a value for communities-at-risk were then classified into 5 classes using the natural breaks algorithm of ArcMap. Those watersheds having no value for communities at risk should be regarded as having a "very low" risk of wildland fire to the wildland-urban interface).
Using the three components mentioned above, the analysis resulted in a final map, Relative Risk to Communities from Wildland Fire in Idaho, sub-watershed level, (Map 2) which displays, by watershed, the areas that are at highest risk/hazard from wildland fire.
These data were designed to characterize mid-scale patterns across Idaho of the the risks of wildland fire to communities. They were developed specifically for use in characterizing relative wildland fire hazard which was then used to assess the risks of wildland fire to communities.
This dataset was used in the "Idaho Interagency Assessment of Wildland Fire Risk to Communities, 2007", Map 2 . It was created for the Statewide Interagency National Fire Plan Working Group to which the Bureau of Land Management (BLM), Idaho is a member. It has also been used in other BLM planning efforts such as Resource Management Plans, Fire Management Plans, and NEPA analysis.
These data were designed to characterize mid-scale patterns of the risk of wildland fire to communities for regional and subregional assessments. The data were intended to be used for prioritizing subwatershed for fuel treatment projects across the state of Idaho.
GENERAL LIMITATIONS
These data were designed to characterize mid-scale patterns across the state of Idaho at a scale of approximately 1:100,000. The use of these data at scales less than 1:100,000 is not recommended without field verification.
The expected accuracy of these data does not warrant its use for geographic extents smaller than approximately 10,000 acres. That is, these data were not designed to be used for "project level" assessments that typically require 1:24,000 scale data.
Are there legal restrictions on access or use of the data?Access constraints: Public
Use constraints:
No warranty is made by the Bureau of Land Management as to the accuracy, reliability, or completeness of these data for individual use or aggregate use with other data.
These data were designed to characterize mid-scale patterns across the state of Idaho at a scale of approximately 1:100,000. The use of these data at scales less than 1:100,000 is not recommended without field verification.
This data set is provided "as-is" without warranty of any kind, including, but not limited to, the implied warranties of merchantability and fitness or a particular purpose. The user assumes all responsibility for the accuracy and suitability of this dataset for a specific application. In no event will the creators or USDA Forest Service be liable for any damages, including lost profits, lost savings, or other incidental or consequential damages arising from the use of or inability to use this data set. Use of these data may require the ability to read ArcInfo Grid datasets.
The expected accuracy of this data set does not warrant its use for geographic extents smaller than approximately 10,000 acres. That is, these data were not designed to be used for "project level" assessments that typically require 1:24,000 scale data.