The Wildland-Urban Interface (WUI) is defined as the location where structures and communities meet or intermingle with undeveloped wildland. In the U.S., over 46 million homes in over 70,000 communities have been built in the WUI. Since 2000 in California alone, an average of over one thousand structures per year have been lost to WUI fires. Despite this significant WUI fire problem, there is little information on fire behavior at the WUI. An improved understanding of WUI fire dynamics is critical to assessing and improving current methods of reducing structure ignitions. The objective of this project is to determine fire behavior at the Wildland Urban Interface (WUI) by developing a WUI fire and ember exposure scale and conducting post fire incident reconnaissance and analysis. The data will be collected through laboratory- and field-scale experiments. Post-fire analysis will be used to identify structural vulnerabilities to WUI fire. These results will be incorporated into the NIST Disaster and Failure Studies Repository and will allow for validation of the NIST WUI Fire Dynamic Simulator computer fire model. The increased understanding and data are being used by standards organizations to guide the development of new standards and provide the scientific basis for new performance-based requirements with the intent to make structures more resistant to firebrand attack. The results of this research will allow improved fire-resistance of building components, structures and communities which will improve the resilience of WUI communities.
Objective: Determine fire behavior at the Wildland Urban Interface (WUI) using post fire analysis and collect data for the development and validation of the NIST WUI Fire Dynamics Simulator (WFDS), leading to a technical foundation for the implementation of the WUI Fire Hazard Scale.
What is the new technical idea? The new technical idea is the creation of an ember and fire exposure scale to document and quantify the severity of WUI fire events. The creation of an exposure scale builds upon the field data collection efforts in coordination with state and local agencies, the development of standardized data collection methodologies (that once implemented will generate reliable post incident data, inclusion of data into NIST’s Disaster and Failure Studies Repository), and the use of the NIST WFDS and targeted lab and field experiments to improve risk assessment and mitigation predictions. Documentation of defensive actions during WUI fire incidents is critical to the understanding of WUI structure survivability and the effectiveness of risk reduction methodologies.
What is the research plan? The Research Plan is developed around two key technical ideas. To quantify the severity of WUI events, both the fire and the thermal exposure to secondary items needs to be characterized. Understanding the thermal exposure (heat and ember fluxes) will enable the reliable performance evaluation of hazard mitigation technologies. A framework will be developed for the acquisition of reliable and useful WUI fire incident data. The collected WUI fire data will be used to identify structure ignition vulnerabilities and guide hazard reduction research including specifically exposure modeling using computational simulations. In more detail, the Research Plan includes the following:
a. Case Studies and Post Incident Data Repository
The NFPA Firewise methodology for WUI fire community protection will be applied to Witch Creek Fire and the validity of the methodology will be assessed. This is possible through extensive data collection conducted during and after the fire. Using the lessons learned during the Witch Fire data collection, a methodology is being developed to collect, store and analyze pre and post-WUI fire data. The joint effort between NIST, CALFIRE and the City of San Diego is aimed at standardizing data collection to ensure that critical data is not lost (due to recovery efforts) and that data compatibility is assured. Different hardware, software and field methodologies are assessed, with the aim of creating a California State data collection infrastructure. The data collected at the Witch Creek Fire will be input in the database and analyzed to determine how structural construction and landscaping attributes affected structure fire performance during the Witch Fire. The database will also be used by WFDS to develop case studies and recreate parts of the Witch Fire.
A comprehensive post-incident field survey, documenting all the structures within the fire perimeter or a community of interest allows a systematic assessment of structure ignition vulnerabilities. Documenting only destroyed and damaged structures can result in erroneous assessments and misleading conclusions with respect to structural vulnerability.1 Data collected from NIST WUI Fire deployments will be integrated into the NIST Disaster and Failure Studies Repository.
b. The National WUI Fire Data Collection Team
A technical collaboration has been developed with the USFS Fire Engineering Research Applications (FERA) Team to develop a national WUI post-fire data collection team. The partnership with the USFS will enable access to WUI fire incidents at a national level. This partnership will use the FERA fuels expertise to capture the exposure from the wildlands to the community. Exposure data will be incorporated into the Hazard Scale.
c. Technology transfer of the NIST WUI data collection methodology.
c. Technology transfer of the NIST WUI data collection methodology.
e. WFDS simulation of WUI wind
f. WUI Fire Data Collection using Unmanned Aerial Vehicles (UAVs)
g. Ignition and Fire Spread Behavior of Structures Adjoining Homes
 For example, at The Trails community in San Diego, CA, the Witch/Guejito fires in 2007 destroyed 74 homes and damaged 16. Out of the 74 destroyed homes 12 had wood shake roofs (of varying ages and treatments), while 37 had Spanish tile roofs (with and without bird stops), 24 had composite roofs and there was one metal roof. The wood shake roofs were present in 16% of the destroyed structures, while the Spanish tile roofs were present in 50% of structures. There were 245 structures within the fire line at the Trails. For the performance of roofs within the fireline 100% of wood shake roofs exposed were destroyed while only 24% of Spanish tile roofs were destroyed. By documenting all structures within the fire line, the relatively high (all other factors being equal) vulnerability of wood shake roofs stands out. While quantifying structure survivability is a complex process that involves construction particulars and measures of fire and ember exposure, the above example illustrates how misleading partial information can be.
 FAA requires that a site specific COA be obtained before an application can be filed for a statewide COA.
 Prescribed burns will be conducted by the US Forest Service and/or the Texas Forest Service.
Realized Research Impacts:
Impact of Standards and Tools:
A member of a joint NIST-Texas Forest Service study team collects data on a Amarillo, Texas, building damaged by wildfires in February 2011. Photo credit: NIST.
Start Date:October 1, 2011
Lead Organizational Unit:el
Related Programs and Projects:
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