WUI Fire Data Collection and Exposure Modeling Project

The Wildland-Urban Interface (WUI) is defined as a location where structures meet or intermingle with undeveloped wildland.  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. Data collected will be used for the development of improved standards and building codes, contributions to the NIST Disaster and Failures Database, planning critical research such as experiments on structural vulnerabilities to WUI fire exposure, and validation of the NIST WUI Fire Dynamics Simulator (WFDS). A first generation hazard mitigation tool will be developed by 2013 along with a fire and ember exposure scale framework.

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 first generation methodology for assessing and mitigating risk in WUI communities by 2014.

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. A fire and exposure scale is needed to quantify the severity of WUI events. The exposure scale 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. In more detail, the Research Plan will include the following research activities:

a.  Case Studies and Post Incident Data Repository
Conduct the Tanglewood Complex fire (Amarillo, TX, 2011) case study and finish the Witch/Guejito case study – findings from these studies will be used to identify structure ignition vulnerabilities and guide hazard reduction research and solutions. The post Witch fire data collection will continue with the support of CALFIRE and the City of San Diego.  The State and City have provided access to the site for NIST personnel during and after the fire.  The analysis is divided into two components.

The first study focused on The Trails subdivision at Rancho Bernardo that was affected by the Witch and Guejito fires (San Diego, CA, 2007). This community of approximately 270 homes was almost entirely within the fire perimeter. Seventy four homes were completely destroyed and sixteen were damaged. The study focused on the development of a timeline for the evolution of fire and structure ignitions throughout the community.

The NFPA Firewise methodology for WUI fire community protection will be applied to The Trails and the validity of the methodology will be assessed. This is possible through extensive data collection conducted during and after the fire. In order to map out the community, NIST, with CALFIRE support, has taken over 11,000 pictures of the destroyed and remaining homes.  A database is being developed to house the Witch and Guejito Fire data (including the pictures) collected in 2007 and 2008 (see Post Fire Incident Methodology).

The second report of the Witch/Guejito fire at The Trails documents why the fire took certain “paths” though the community and why certain structures burned, while others survived. The report used, for the first time, exposure and defensive actions to document structure performance and to identify the effectiveness of hazard reduction technologies.

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 wide data collection infrastructure. The data collected at The Trails will be input in the database and analyzed to determine how structure construction and landscaping attributes affected structure fire performance during the Witch Fire. This database will also be used by WFDS to develop case studies and recreate parts of the Witch Fire.

The database is Geographic Information System (GIS) based. The plot and structure particulars collected including damage to vegetation will be included in the database along with the defensive actions documented in the first report. The GIS framework will enable spatial queries of the data. The dynamic framework will allow for expansion of the collection fields if future data collections identify additional features of interest.

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.

The NIST WUI data collection methodology was used to train the Texas Forest Service in October 2010 and was field tested during the initial reconnaissance deployment in response to the fires around Amarillo, Texas in February 2011. The method was also used during the Bastrop Complex Fire in Texas in 2011, the most destructive WUI fire in the State’s history.

b.  The National WUI Fire Data Collection Team
The NIST WUI data collection efforts to date (Witch 2007 and Tanglewood Complex 2011) were accomplished through partnerships with CA and TX. While this model has proved successful a national framework is necessary in order to respond to WUI incidents in other states. The development of a National Fire Data Collection Team will be developed in partnership with the US Forest Service. The National Team will enable access to fires in all states. The utilization of highly trained personnel, together with the developed QA/QC plan, will ensure data consistency and reliability. The National WUI Fire Data Collection Team will be used to collect detailed WUI community fire response data.

A technical partnership has been developed with the USFS Fire Engineering Research Applications (FERA) Team. The new technical ideas associated with this partnership are:

• 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 is in contrast to the state-centric approach used to date between NIST, CA and TX.
• Use the FERA fuels expertise to capture the exposure from the wildlands to the community. The NIST built environment expertise will be augmented by the USFS wildland and residential vegetative fuels expertise. The exposure from vegetative fuels in the wildlands is the missing link in characterizing the threat to structures in a community. Exposure information will be used to develop the foundation for a national WUI fire exposure or intensity scale.
• Information sharing on field wind data, which will assist with WFDS model validation and help characterize WUI fire exposure severity. 

c.  Wide spread use of NIST developed WUI data collection methodology.
To date there has been no standardized approach to collect basic WUI community fire response data at a national level. The NIST WUI 1 data collection methodology was designed to address this need. The widespread use of the NIST developed WUI 1 data collection methodology will generate a usable data set of what structures are burning in the WUI. This information will be used to guide the National WUI Fire Data Collection Team deployments. Data collected from WUI Fire deployments by trained personnel will be integrated into the NIST Disaster and Failure Studies Repository.

A post –WUI fire data collection deployment is scheduled for September-December 2012 in southern CA. Training for the deployment team has been scheduled for July 2012, with a mock deployment exercise in August.

d.  Develop a WUI Exposure Scale – concept developed
There is a critical lack of quantitative information on the assault on structures from embers and fire. This is due, in part, to the lack of a common scale for quantifying this exposure. An exposure scale can be used to successfully improve the building codes and standards as well as the building practices to meet the survivability requirements of structures in certain fire and ember exposure environments.

Unlike a hurricane that gets an overall rating based on maximum sustained winds, a WUI fire, being so dynamic and variable in space and time will not get a single rating. The exposure is location specific and not incident specific, therefore an incident or fire can have many rating depending on the local conditions. The framework for a WUI exposure scale will be developed and used to guide current and future WUI research as well as developments in codes, standards and best practices.

e.  WFDS simulation of WUI wind
Wind, topography and fuels are the main attributes that affect WUI fire behavior. The presence of severe winds such as the Santa Ana’s or the winds seen in the Texas panhandle can produce extreme fire behavior. The focus of this effort will be in developing wind predictive capabilities. This will be accomplished through coupled experimental and modeling work at parcel, community and landscape scales. This will be done in collaboration with NOAA, the National Center for Atmospheric Research (NCAR) and the US Forest Service.

Instrumentation characterization will be conducted specifically with respect to comparing aerial wind sensor and SODAR^[2] data. USFS funding will be leveraged to collect critical wind data during prescribed burns. Prescribed burns will be conducted by USFS and Texas Forest Service specifically for the development and validation of WFDS.

f.  Unmanned Aerial Vehicles (UAVs) – New Activity
UAVs are essential for collecting critical prescribed fire behavior information. Participation in prescribed burns^[3] will typically occur during the winter/spring months. Participation during future post fire field deployments will occur during the summer/fall months.^[4]

g.  Ignition and Fire Spread Behavior of Structures Adjoining Homes
A new series  of live fire burn experiments is planned to examine ignition and flame spread of wood fences and piles of fire wood.  There is a lack of information on the ignition of and flame spread along structures and materials adjoining homes such as fences, wood piles, mulch, landscape borders, and ornamental vegetation and what role these have in the ignition of homes.  Research is required on common materials and construction assemblies to determine what the ignition and fire behaviors are and which combinations perform relatively better and worse.  This quantitative knowledge is necessary to technically support the development of science-based codes, standards, and best practices that homeowners and communities need to prevent or minimize WUI fire ignition and spread to homes due to the landscape features around the homes.

h.  Technology transfer
Technology transfer will be accomplished on the framework developed by the WUI exposure scale. Specifically the WUI exposure scale will enable the codes, standards and best practices to reflect the hazard reduction requirements associated with specific exposure conditions. Cost effective solutions will be enabled both for new construction as well as retrofit by building to meet specific WUI exposure requirements. Technical partnerships have been developed with key stakeholders from Codes and Standards organizations to key state agencies to enable this technology transfer.

 

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[1] 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.

[2] SODAR(Sonic Detection And Ranging) is a meteorological instrument used to remotely measure the wind profile and vertical turbulence structure in lower levels of atmosphere.

[3] Prescribed burns will be conducted by the US Forest Service and/or the Texas Forest Service.

[4] A Certificate of Authorization (COA) was obtained from the Federal Aviation Administration. The COA has enabled NIST to conduct acceptance testing of the ARRA purchased UAVs. The UAVs were successfully flown at the Winn Ranch, in Wimberley, Texas. Proficiency testing to meet FAA requirements is scheduled throughout the upcoming year. A COA for the entire state of Texas will be submitted and work will begin for a site specific COA in California.  SOPs are driven by the FAA COA requirements and the training and SOPs provided by the vendor. The FAA is mandating all air operations, while all ground activities are specified by the UAV manufacturer and accepted by FAA.

 

Recent Results:

• Completed unmanned aerial vehicle (UAV) flights – initial series 4/2012.
• Completed initial characterization of UAV instrumentation capabilities, 7/2012
• Output: NIST TN 1635, A Case Study of a Community Affected by the Witch and Guejito Fires
• Output: NIST TN 1708, Initial Reconnaissance of the 2011 Wildland-Urban Interface Fires in Amarillo, Texas
• Output: NIST TN 1748, report on Characterizing WUI Fire Exposures
• Outcome: WUI Fire Exposure scale (presented at NIST WUI Fire Research Needs Workshop in CO, August 2012). 
• Impact: Bastrop Complex Fire – NIST/USFS data collection methodology used for documentation and analysis of worst WUI fire in Texas history (2012)

Standards and Codes: This project will focus on incorporating the exposure scale into building codes and standards including the 2012 International Wildland-Urban Interface Code (ICC), the 2009 Wildland Urban Building Code, California Chapter 7A Building Code, and the 2013 Standard for Reducing Structure Ignition Hazards from Wildland Fire (NFPA 1144).   Researchers  are members and participate in the Fire/Performance/Wildland-Urban Interface Committee, FI PC WU –ICC (Bryner)  and  the Technical Committee on Forest and Rural Fire Protection (Maranghides), Quantification of Exterior Fire Exposures, ASTM E05.14 (Manzello).  The economic analysis results will be incorporated into NFPA 1144 Committee on Forest and Rural Fire.