Wildland Urban Interface, Wildland Urban Intermix, and Wildfire Influence Zones developed by FRAP for the FRAP 2015 Assessment.

This dataset is derived from several data sources, including housing density (input_lsn_HousingDensity12_2), Fire Hazard Severity Zones (FHSZ_Assessment11_1), Unimproved Parcels (input_UnimprovedParcels16_1) , and Vegetation Cover (input_FVEG15_2).

Spatially accurate representation of the nexus between development and wildfire is underpinned in this dataset by the use of Landscan 2012. Assessment dataset input_lsn_HousingDensity12_2 has four housing density classes: Specifically, remote sensed night time light emissions (Conus Night) data is converted to points, summarized into projected 90m grid cells using methods guided by the West Wide Wildfire Risk Assessment Final Report - Addendum I Detailed Technical Methods, March 31, 2013. The data is then resampled to 30m for consistency with other Assessment data products.

Housing Density Classes (DEN4) used in the WUI definitions:

Class Definition

1 Less than one house per 20 acres

2 One house per 20 acres to one house per 5 acres

3 More than one house per 5 acres to 1 house per acre

4 More than 1 house per acre

Interface:

• DEN4 Class 2, 3 or 4

• In Moderate, High, or Very High Fire Hazard Severity Zone

• Not dominated by wildland vegetation (i.e., Lifeform not Herbaceous, Hardwood, Conifer or Shrub according to dataset input_FVEG15_2 )

• Spatially contiguous groups of 30m cells that are 10 acres and larger

Intermix:

• Not Interface

• DEN4 Class 2

• DEN4 Class 3, 4 dominated by wildland vegetation

• In Moderate, High or Very High Fire Hazard Severity Zone

• Improved Parcels only

• Spatially contiguous groups of 30m cells 25 acres and larger

Wildfire Influence Zone

• Wildland vegetation up to 1.5 miles from Interface or Intermix

Fire Hazard Severity Zones:

PRC 4201 - 4204 and Govt. Code 51175-89 direct the California Department of Forestry and Fire Protection (CAL FIRE) to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors. These zones, referred to as Fire Hazard Severity Zones (FHSZ), define the application of various mitigation strategies to reduce risk associated with wildland fires. CAL FIRE is remapping Fire Hazard Severity Zones (FHSZ) for State Responsibility Areas (SRA) and Very High Fire Hazard Severity Zones (VHFHSZ) recommendations in Local Responsibility Areas (LRA) to provide updated map zones, based on new data, science, and technology. Offical "Maps of Fire Hazard Severity Zones in the State Responsibility Area of California" are provided as required by Public Resources Code 4201-4204 and entitled in the California Code of Regulation, Title 14, Section 1280 Fire Hazard Severity Zones, and as adopted by CAL FIRE on November 7, 2007. Maps of the adopted zones in SRA are available at: http://frap.cdf.ca.gov/projects/hazard/fhz.html. More information about the project can be found at: http://frap.cdf.ca.gov/projects/hazard/hazard.html.

Fire Hazard Severity Zone is designated by the HAZ_NUM field, where 1=Moderate, 2=High, 3=Very High (SRA), 4=Very High (LRA). Source: State Resposibility Areas: fhszs06_3; Local Responsibility Areas: fhszl11_1).