Wildland-Urban Interface (WUI) Fire Data Collection on Parcel Vulnerabilities

Summary

Gaining a deeper understanding of Wildland-Urban Interface (WUI) fire dynamics and the mechanisms of structure ignition is crucial for enhancing the resilience of structures and communities to WUI fires. This project focuses on advancing the science of WUI fires through post-fire data collection, case studies, and laboratory experiments to reduce community losses, including fatalities, injuries, and property damage.

The insights gained from this research inform the development of new codes and standards aimed at improving the fire resistance of structures and reducing vulnerability to firebrand attacks. The findings are shared with communities and standards organizations to provide a scientific foundation for the creation of performance-based mitigation strategies. Ultimately, the results will lead to more fire-resistant building materials and designs, strengthening the safety and resilience of communities vulnerable to WUI fires.

Description

Objective
To develop the measurement science needed to mitigate the effects of wildland-urban interface (WUI) fires by providing technical guidance for structures, landscaping elements, and community designs that resist ignition and limit the spread of WUI fires.

Technical Idea
Developing effective and implementable WUI fire mitigation requires understanding of real-world structure ignition vulnerabilities, quantification of expected fire and ember exposures, and appropriate structure hardening and parcel-level fuel management.

Post-fire data collection and analysis reveal how WUI fire behavior is driven by the interactions among fuel, weather, and terrain, and the roles played by heat, embers, and direct flame impingement. Pathways for fire may implicate structure design, materials, and landscaping elements. Post-fire analysis also shows how fire behavior is modified by defensive actions, both active and passive. Documentation of defensive actions during WUI fire incidents is critical to the understanding of WUI structure survivability and the effectiveness of risk reduction methodologies.

Developing a deep understanding of how WUI fire incidents progress, how fire spreads through the built environment, and how people and first responders take action to save lives and property, can improve community preparedness and resilience to future fires.

Structure ignition vulnerabilities observed and identified through post-fire analysis of communities exposed to WUI fires also informs more focused laboratory experiments. Full-scale experiments of parcel, landscaping, and structural fuels will help to quantify WUI fire exposures and identify and test vulnerabilities and relevant mitigation approaches. Experiments include the effects on WUI fire spread of interactions among combustible and non-combustible parcel-level fuels, design features of the structure and building assembly, and the spatial relationship between WUI fuels. Mitigation techniques are needed for both existing structures and for new construction. The new insights from this project will be incorporated into the design of new buildings and communities and retrofitting of existing buildings.

With this combined field and laboratory knowledge, structure and community vulnerabilities to WUI fires can be better mitigated through development of fire-resistant design and advanced materials, based on reliable post-incident data and analysis, and promoted through incorporation into codes, standards, and best practices.

Research Plan
The research plan proceeds from obtaining an understanding of the vulnerabilities of structures and communities, finding ways to address them, and disseminating the new knowledge.

Case Studies

Post-fire data collection and analysis on WUI fires identify vulnerabilities for structures, parcels, and communities and illuminate the roles of defensive actions, fuel management, and mitigation strategies in modifying the event and reducing the hazard. Evaluation of home and community mitigation performance requires long-term detailed post-fire research to establish the timeline and locations of defensive actions throughout the community, in addition to an investigation of structural damage and exposure to fire and embers. Due to the complexities of fire behavior and the destruction of supporting data by the fire itself, many questions must be subsequently investigated in more detailed laboratory experiments. Therefore, case study analysis results help to set the experimental research agenda.

Future post-fire deployments will seek to add to the knowledge obtained in previous case studies on four major fires:  the Witch Creek-Guejito Fire (San Diego County, CA, 2007), the Tanglewood Complex (Amarillo, TX, 2011), the Waldo Canyon Fire (Colorado Springs, CO, 2012), and the Camp Fire (Butte County, CA, 2018). Planning for deployments includes: identifying the WUI event criteria for data collection that will direct future research; establishing contacts; pre-planning with local Authorities Having Jurisdiction; identifying and preparing data collection and analysis methodologies and tools; and training of field data collectors. Data collection methodologies that were standardized during previous case studies will be updated in collaboration with partners. Collaborations with national, state, and local organizations collecting WUI community data pre- and post-fire will continue to be pursued, with the goals of continuing to develop best practices and of adding to the body of knowledge on the vulnerabilities of structures and communities to WUI fires.

Laboratory/Field Experiments

Analysis of post-fire data has identified key vulnerabilities of buildings to WUI fires, including structural components and parcel-level fuels such as fences, decks, sheds and other auxiliary structures, furniture, woodpiles, landscaping timbers, ornamental vegetation, mulch, and leaf litter.

More research is needed to understand ignition and flame spread along these materials adjoining homes, as well as the role that they play in the ignition of buildings. Experiments will help quantify the fire and ember exposures generated by combustible materials on the parcel under a variety of conditions. The capability of mitigation approaches to reduce the fire exposures generated by these fuels will also be tested. The results will be used to develop WUI building codes, standards, and best practices for homeowners and communities.

Technology Transfer

Knowledge learned from both post-fire case studies and experiments must make it into the hands of practitioners and communities at risk of WUI fire. Before, during, and after any WUI fire event, decisions that can reduce losses from WUI fires are made by people at all levels within the community. At the community level, improvements to codes and standards must be adopted and enforced to fully realize the benefits. At the organizational level, firefighter situational awareness is key to decisions made about evacuation or firefighting action during a WUI fire event. At the individual and household level, people may modify their properties before a fire to mitigate its effects, must respond to a fire as it approaches, and need to deal with the aftermath of the fire as it has affected them. Disseminating research knowledge to relevant audiences, including codes and standards organizations, Authorities Having Jurisdiction and policymakers, and local communities and homeowners at risk to WUI fire, is a key aspect of the research plan.

Major Accomplishments

• The NIST WUI Structure/Parcel/Community Fire Hazard Mitigation Methodology (HMM) provides guidance to communities about what changes and mitigation approaches are necessary to better protect structures and communities from WUI fires.
• Lessons learned about life safety considerations for no-notice WUI fire events when there is not enough time to evacuate led directly into guidance and recommendations for a paradigm shift and advance evacuation planning and community preparedness.
• Detailed study of the Camp Fire identified the influence of widespread spot fire ignitions, community fire spread pathways, burnovers, temporary refuge areas, and rescues on fire spread and life safety during the catastrophic fire.
• Dozens of experiments burning combustible fences and woodpiles quantified the hazard of these common parcel-level fuels, which increase local exposure of fire and embers and facilitate fire spread through WUI communities.