Wildfire Risk to Communities Flame Length Exceedance Probability - 8 foot (Image Service)

The data included in this publication depict the 2024 version of components of wildfire risk for all lands in the United States that: 1) are landscape-wide (i.e., measurable at every pixel across the landscape); and 2) represent in situ risk - risk at the location where the adverse effects take place on the landscape. National wildfire hazard datasets of annual burn probability and fire intensity, generated by the USDA Forest Service, Rocky Mountain Research Station and Pyrologix LLC, form the foundation of the Wildfire Risk to Communities data. Vegetation and wildland fuels data from LANDFIRE 2020 (version 2.2.0) were used as input to two different but related geospatial fire simulation systems. Annual burn probability was produced with the USFS geospatial fire simulator (FSim) at a relatively coarse cell size of 270 meters (m). To bring the burn probability raster data down to a finer resolution more useful for assessing hazard and risk to communities, we upsampled them to the native 30 m resolution of the LANDFIRE fuel and vegetation data. In this upsampling process, we also spread values of modeled burn probability into developed areas represented in LANDFIRE fuels data as non-burnable. Burn probability rasters represent landscape conditions as of the end of 2020. Fire intensity characteristics were modeled at 30 m resolution using a process that performs a comprehensive set of FlamMap runs spanning the full range of weather-related characteristics that occur during a fire season and then integrates those runs into a variety of results based on the likelihood of those weather types occurring. Before the fire intensity modeling, the LANDFIRE 2020 data were updated to reflect fuels disturbances occurring in 2021 and 2022. As such, the fire intensity datasets represent landscape conditions as of the end of 2022. Additional methodology documentation is provided in a methods document (\Supplements\WRC_V2_Methods_Landscape-wideRisk.pdf) packaged in the data download. The specific raster datasets in this publication include: Risk to Potential Structures (RPS): A measure that integrates wildfire likelihood and intensity with generalized consequences to a home on every pixel. For every place on the landscape, it poses the hypothetical question, "What would be the relative risk to a house if one existed here?" This allows comparison of wildfire risk in places where homes already exist to places where new construction may be proposed. This dataset is referred to as Risk to Homes in the Wildfire Risk to Communities web application. Conditional Risk to Potential Structures (cRPS): The potential consequences of fire to a home at a given location, if a fire occurs there and if a home were located there. Referred to as Wildfire Consequence in the Wildfire Risk to Communities web application. Exposure Type: Exposure is the spatial coincidence of wildfire likelihood and intensity with communities. This layer delineates where homes are directly exposed to wildfire from adjacent wildland vegetation, indirectly exposed to wildfire from indirect sources such as embers and home-to-home ignition, or not exposed to wildfire due to distance from direct and indirect ignition sources. Burn Probability (BP): The annual probability of wildfire burning in a specific location. Referred to as Wildfire Likelihood in the Wildfire Risk to Communities web application. Conditional Flame Length (CFL): The mean flame length for a fire burning in the direction of maximum spread (headfire) at a given location if a fire were to occur; an average measure of wildfire intensity. Flame Length Exceedance Probability - 4 ft (FLEP4): The conditional probability that flame length at a pixel will exceed 4 feet if a fire occurs; indicates the potential for moderate to high wildfire intensity. Flame Length Exceedance Probability - 8 ft (FLEP8): the conditional probability that flame length at a pixel will exceed 8 feet if a fire occurs; indicates the potential for high wildfire intensity. Wildfire Hazard Potential (WHP): An index that quantifies the relative potential for wildfire that may be difficult to manage, used as a measure to help prioritize where fuel treatments may be needed. Additional methodology documentation is provided with the data publication download. (https://www.fs.usda.gov/rds/archive/Catalog/RDS-2020-0016-2) Note: Pixel values in this image service have been altered from the original raster dataset due to data requirements in web services. The service is intended primarily for data visualization. Relative values and spatial patterns have been largely preserved in the service, but users are encouraged to download the source data for quantitative analysis.本出版物收录的数据为2024版美国全境野火风险组分数据集，满足以下两项条件：1） 覆盖全域景观（即可在景观全范围的每个像元上进行量化）；2） 表征原位风险——即负面影响发生在景观对应位置处的风险。 本数据集以美国农业部林务局（USDA Forest Service）落基山研究站与Pyrologix LLC生成的年度燃烧概率与火灾强度国家级野火危险性数据集为核心基础。研究采用LANDFIRE 2020（版本2.2.0）的植被与野外可燃物数据作为两套独立但相关的地理空间火灾模拟系统的输入数据。 年度燃烧概率通过美国林务局地理空间火灾模拟器（FSim）生成，初始像元分辨率相对较粗，为270米。为将燃烧概率栅格数据分辨率提升至更适用于社区危险性与风险评估的精细尺度，研究将其重采样至LANDFIRE可燃物与植被数据原生的30米分辨率。在此次重采样过程中，研究同时将模拟得到的燃烧概率数值赋值至LANDFIRE可燃物数据中标记为不可燃的建成区范围内。燃烧概率栅格数据表征的是2020年末的景观状况。 火灾强度特征以30米分辨率进行建模，具体流程为：全面运行FlamMap模拟，覆盖火灾季内所有气象相关特征的变化范围，随后依据各类气象类型的发生概率，将模拟结果整合为多类输出成果。在开展火灾强度建模前，研究已对LANDFIRE 2020数据进行更新，以反映2021年与2022年发生的可燃物扰动情况。因此，火灾强度数据集表征的是2022年末的景观状况。 详细的方法学文档已收录于数据下载包中的SupplementsWRC_V2_Methods_Landscape-wideRisk.pdf文件内。 本出版物包含的具体栅格数据集如下： 1. 潜在建筑野火风险（Risk to Potential Structures, RPS）：该指标将野火发生可能性、火灾强度与单栋住宅的广义受灾后果进行耦合，每个像元对应一个计算值。针对景观中的任意位置，该数据集提出了一个假设性问题：“若此处存在一栋住宅，其面临的相对野火风险为多少？”借此可对比已有住宅区域与拟新建住宅区域的野火风险水平。在《社区野火风险》（Wildfire Risk to Communities）网页应用中，该数据集被称为“住宅野火风险”。 2. 潜在建筑条件性野火风险（Conditional Risk to Potential Structures, cRPS）：表征特定位置若发生火灾且该处存在住宅时，住宅面临的潜在受灾后果。在《社区野火风险》网页应用中，该数据集被称为“野火受灾后果”。 3. 暴露类型（Exposure Type）：暴露性指野火发生可能性与火灾强度和社区的空间重合度。该图层可区分三类区域：住宅直接受周边野生植被引发的野火影响区域、住宅通过余烬、住宅间引燃等间接途径受野火影响的区域，以及因距离直接/间接引燃源过远而未受野火影响的区域。 4. 燃烧概率（Burn Probability, BP）：表征特定区域年度内发生野火的概率。在《社区野火风险》网页应用中，该数据集被称为“野火发生可能性”。 5. 条件火焰长度（Conditional Flame Length, CFL）：若特定位置发生火灾，沿最大蔓延方向（火头）燃烧时的平均火焰长度，是野火强度的平均衡量指标。 6. 火焰长度超4英尺概率（Flame Length Exceedance Probability - 4 ft, FLEP4）：若发生火灾，单个像元处火焰长度超过4英尺的条件概率，用于表征野火达到中高强度的潜在可能性。 7. 火焰长度超8英尺概率（Flame Length Exceedance Probability - 8 ft, FLEP8）：若发生火灾，单个像元处火焰长度超过8英尺的条件概率，用于表征野火达到高强度的潜在可能性。 8. 野火危险性潜力指数（Wildfire Hazard Potential, WHP）：该指数用于量化难以管控的野火相对发生潜力，可作为优先确定可燃物处理区域的参考依据。 本数据出版物下载包中还附带了额外的方法学文档（链接：https://www.fs.usda.gov/rds/archive/Catalog/RDS-2020-0016-2）。 注意：由于网页服务的数据要求，本影像服务中的像元数值已与原始栅格数据集有所调整。本服务主要用于数据可视化，其保留了大部分相对数值与空间格局，但建议用户下载原始数据用于定量分析。