Every year in the United States, more than 3,000 homes are destroyed by wildland/urban interface (WUI) fires. Given the magnitude of these losses, the fire service needs a more consistent and complete method of post-fire data collection that can be shared and implemented on a national scale. The database that could be generated would support a more quantitative assessment of which construction and landscaping attributes contribute to structure ignition.
In answer to that issue, the National Institute of Standards and Technology’s (NIST’s) Disaster and Failures Studies Program was designed to help increase the resilience of communities in the aftermath of disasters, including WUI fires. As part of the program, equipment and a methodology have been developed to better assess and document the damages to a community caused by WUI fire. These assessments and documentation can help determine specifically what is burning and why; this information is also being used to improve building codes and practices in order to reduce losses from future WUI events.
Studying The Trails
In 2007, the NIST WUI Team was invited by the California Department of Forestry and Fire Prevention (CAL FIRE) to collect post-incident data from the October 2007 fires in California. NIST was invited to work with CAL FIRE on documenting the WUI fire event and identifying structure construction vulnerabilities. This resulted in a case study1 at The Trails development of Rancho Bernardo, located 25 miles north of downtown San Diego. This area was burned by the Witch and Guejito fires, two of several destructive fires that ravaged Southern California in 2007. There were 274 homes in The Trails community, including 245 within the fire perimeter. In all, 74 homes were destroyed and 16 were partially damaged.
The NIST data-collection effort provided information needed to characterize 1) the nature and direction of the fire’s approach from the wildlands, 2) the effects of fire within the community and 3) the defensive actions that were taken. The intent was to collect sufficient information, not only to characterize the overall fire behavior in the WUI, but also to provide a foundation for future case studies. Key findings from the first report of the case study include:
- The Guejito Fire approached The Trails at a fire spread rate of 9 km/h.
- The arrival of the wildland firefront, not the preceding embers, caused the majority of the damage and overwhelmed first responder resources.
- More than 50% of the structures were ignited within three hours after the main front of the Guejito Fire hit the community.
- It’s estimated that 29 of the destroyed structures (40%) were burning at the same time.
- Direct ember ignitions accounted for one out of every three destroyed homes.
- Embers were responsible for the ignitions of structures on the perimeter and in the interior of the community.
- Two out of every three destroyed homes were ignited directly or indirectly by embers.
- 40% of structures on the perimeter were destroyed compared to 20% in the interior of the community.
- Direct embers ignitions occurred from the arrival of the wildland fire front through the next nine hours.
- 60% of defended structures on fire were saved.
- 70% of the destroyed homes were not defended.
- Defensive actions were taken on one out of every three homes in The Trails.
- 15 out the 16 damaged homes were successfully defended.
The NIST Data-Collection Method
Following the Witch/Guejito fire data collection and analysis effort, NIST developed a two-phase data-collection method. Phases 1 and 2, or WUI 1 and WUI 2, are summarized below:
WUI 1: Single-form data collection
Phase 1, or WUI 1, data collection involves a single-page data-collection form, a digital camera and a GPS unit. The single-page form is filled out for all structures within the fire perimeter, not just the structures that were damaged or destroyed. This is a critical step, as it enables agencies to completely assess the vulnerabilities of structures in the WUI.
A national WUI 1 database is being developed to house all the WUI 1 field data. An online training and accreditation program will enable qualified personnel to collect WUI 1 data and provide them for inclusion in the National Disaster Database at NIST.
The WUI 1 data-collection process was tested at the Willow Creek Fire, and the WUI 1 field data collection and data storage effort will become operational in 2013. Interested municipalities should contact the authors for additional information.
WUI 2: GIS-based data collection, including timeline reconstruction
Phase two, or WUI 2, involves collecting data via geographic information system (GIS) tools. The data is collected in the field and stored in the database at a parcel level. The database is assembled through a combination of field/office data collection and production activities. Field data collection occurred through the use of GIS-enabled tablet PCs.
Data Collection with the TFS
More recently, in October 2010, NIST and the Texas Forest Service (TFS) worked together to train TFS personnel on the NIST WUI data-collection method. The NIST equipment was pre-staged in Texas, and several field training exercises were conducted to maintain data-collection proficiency.
The fires burning around Amarillo in February 2011 provided a unique opportunity for NIST and the TFS to document WUI fire losses and fire behavior. The joint NIST/TFS team was deployed within 44 hours of ignition. Field measurements were made at the Willow Creek and Tanglewood Complex fires. (A third fire in the Amarillo area, referred to as the Country Club Fire, was not studied because of the limited damage to structures.)
Preliminary findings indicate that:
- Buffalo grass, even when mowed, carried fire on residential yards and wildlands.
- Certain foundation constructions (pier and beam), as well as modular/mobile homes, may exhibit certain ignition vulnerabilities.
- Statewide pre-deployment of firefighting resources using the Texas Intrastate Fire Mutual Aid System (TIFMAS) was effective in rapidly getting resources to the fires.
- Extensive defensive actions were identified in the Tanglewood Complex Fire.
Note: A complete preliminary report of the deployment is now available online.2 A second, more detailed, technical report will provide a reconstruction of the event timeline and general fire behavior observations. The second report will also document how structure survivability was influenced by defensive actions, structure attributes, landscaping characteristics, topographical features and wildland fire exposure.
It’s also important to note that during this deployment, the NIST WUI field data-collection methods were, for the first time, integrated into the Incident Command System’s logistics and standard operating procedures (SOPs).
Deployment Details & Tips
Rapid team deployment is critical to collecting reliable post-fire WUI data. In the Amarillo deployment, data collection was initiated 44 hours after fire ignition, and the analysis processes ran continuously, 24 hours a day, for the duration of the three-week field deployment.
A daily safety brief was conducted each day at 0700 hrs, with field data collection occurring during daylight hours. At the end of each field day, all the land-parcel data was uploaded into the WUI 2 database. This included building and landscaping attributes as well as fire behavior reconstruction observations. The creation of field maps and initial quality assurance/quality control was performed overnight. New data, including high-resolution imagery, was then loaded onto researchers’ tablet PCs for data collection in the field the following day.
Timeline reconstruction is a critical part of the WUI 2 data-collection method. This is accomplished primarily by holding technical discussions with first responders to collect timeline information, such as radio logs and time-stamped images or video.
Extensive defensive actions were taken by local and non-local fire departments during the Tanglewood Complex Fire. The actions will be documented in the full technical report.
Future Data Collection
Currently, NIST is working together with the U.S. Forest Service Fire and Environmental Research Applications Team (FERA), based in Seattle, and the San Diego Fire-Rescue Department to assemble a rapid response team of WUI 1 and WUI 2 field data collectors to respond to WUI fires in the southwestern United States. WUI Rapid Response Team training is scheduled for the summer of 2012 in San Diego. The next deployment is planned for the fall 2012.
Given the increasing size and scope of wildland/WUI fires, these data-collection teams will become increasingly important to fire agencies. If we can determine specifically how WUI fires start and spread, and share that information on a national scale, we can potentially prevent the destruction of thousands of acres of land and structures, and save countless lives.