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Q2 2020 Technical Articles:
Defensible Space: Combating the Challenges of Wildfire Mitigation
Please find this quarter's featured article "Defensible Space: Combating the Challenges of Wildfire Mitigation" below:
COMBATING THE CHALLENGES OF WILDFIRE MITIGATION
Combating the Challenges of Wildfire Mitigation
BY MICHAEL J. GOLLNER, PhD
OVER THE PAST FEW YEARS, wildfires have caused immense destruction around the world. In the United States, California has become ground zero for wildfire disasters, with 2017
and 2018 representing some of the largest losses of life and property in a century. The Mendocino complex fire in 2018 burned over 450,000 acres, the largest in California history. However, the much smaller Camp Fire caught the national
attention for taking 86 lives and consuming nearly an entire community. The recent 2019 –2020 Australian bushfire season, with over 46 million acres burned and 34 deaths, has demonstrated this global problem will only get worse unless
we change the way we address it.
The effect large wildfires have on people — lives lost, communities destroyed, critical natural resources wiped out — is a large part of what transforms a natural process into a human disaster. Increasingly, large populations are affected
by wildfires, even indirectly by health effects from smoke exposure, large-scale preventative power shutoffs, and post-fire landslides. With a growing population in the Wild-land-Urban Interface (WUI), where natural lands and human
development meet, it is critical that fire protection engineers play an increasing role in fire prevention. Our unique skill set is well-adapted to WUI fires, but we must shift our thinking to community-scale fire hazards that are
strongly coupled to the surrounding landscape.
We often hear of two major reasons for destructive wildfires: ignitions from power transmission lines and climate change. Both are critically important issues and are literally changing the landscape of fire. However, tackling these issues
alone will not result in the changes needed to prevent the dramatic destruction of communities and widespread health effects experienced. Neither will an ever-increasing budget focused on suppression. Instead, we must take what we
have learned about wildfires and apply it to implementing dramatic changes to the way we build our homes, plan communities, and manage our natural lands.
California, like many other natural ecosystems, has always had fire.Indigenous people used fires to manage their landscape,and there were devastating fires
long before we changed land management practices. Smokey the Bear exemplifies our current problems, as one of the most successful advertising campaigns in history — and perhaps one of the biggest failures for wild-land fire management.By
suppressing every small fire, we have left a massive buildup of fuels less resilient to change.
This has been exacerbated by climate-related issues, such as beetle-killed trees which now line some of our forest floor. Because we are so good at extinguishing fires 98% of the time, we leave these massive buildups of fuel to burn only
during the most critical fire conditions, the worst weather days where hot, dry winds make it nearly impossible to stop an advancing fire front. How these severe weather events will be affected by climate change is a source of debate,
but the most recent trend is that these conditions are getting worse.
Focusing solely on preventing ignition sources, therefore, perpetuates the problem that has been growing over a landscape no longer able to cope with fire. In California, most ignitions are human caused over 84% nationwide and unfortunately, we’ve seen a number of devastating fires caused by power lines. This makes sense because high winds affect power transmission infrastructure and incredibly dry fuels nearby are needy recipients of sparks, ready to
spread fires throughout the landscape. Unfortunately, power lines aren’t the only source of ignitions. The largest wildfire in California history, the Mendocino fire, was caused by an errant strike of a hammer.Other
instances include chains dragged behind vehicles, lawn equipment, even falling rocks.
With more critical fire danger — dry fuels, low humidity, high winds — the easier any potential spark can generate a fire that rapidly grows and intensifies. Populations have dramatically increased in the WUI, where development abuts undeveloped
lands that can and will burn. The very presence of people exacerbates the risk of ignitions, and also places more people in harm’s way. Removing ignition sources is a noble task, but how do we make a difference if nothing we do can
guarantee stopping these fires on the worst fire days?
As a society, we must recognize that we can’t and won’t stop all fires. Focusing on better landscape management — including adding prescribed fires, reducing hazardous fuels near communities, and allowing some fires to burn under mild
conditions — will lower the intensity of fires our communities are exposed to. There are many challenges here, as there is always some risk from a fire, even under controlled conditions. There is often public backlash from reducing
fuels on landscapes, local smoke exposure, and the previously mentioned risk from any fire. But without these smaller fires, we will be forced to contend only with the most extreme fire events.
As a community, we must make it harder for these fires to spread into urban areas. Most of this task focuses on structures and infrastructure, e.g. homes and businesses, but also critical infrastructure such as hospitals, power, water,
evacuation routes, and communications. Fire protection engineers have a key role, implementing our extensive knowledge of passive fire protection to the exterior, rather than the interior of buildings. “Hardening” communities from
fire is possible with moderate changes. Modifications can be made to homes to prevent ignition from embers, such as screens on vents, non-combustible building materials, and constant maintenance removing flammable litter. Defensible space keeps fires from getting close enough to ignite structures and give
firefighters a safe place to protect those structures as the fire approaches. Importantly, a 5-foot (1.5 meters) zone around a structure that is completely free of combustible materials, including mulch and wood fences, helps keep
potential flames further from homes, decreasing the risk of ignition.
Implementing these recommendations is hard. Defensible space requires constant maintenance, and therefore, inspections and enforcement. The adoption and enforcement of codes and standards for WUI fire protection is significantly behind
the built environment. There are some great community-based programs that help, such as Fire-wise and Fire Adapted Communities; however, it takes a grass-root effort and typically occurs in communities already affected by fire. As
seen in the Santa Rosa Coffey Park neighborhood destroyed by the 2017 Tubbs Fire, even a severely destructive event can fail to motivate adoption of stringent new building standards. There is also a continued challenge of renovating
existing buildings to replace flammable wood roofs, siding, and decks, which can be prohibitively expensive for many of the most vulnerable individuals in at-risk communities. New mechanisms, such as community and homeowner grants
and specialized workforce development, will be needed to make large-scale changes.
All these changes require extensive cooperation between residents, first responders, and public policy makers. Efforts such as development of a Community Wildfire Protection Plan (CWPP) are critical in looking at local resources, hazards,
and potential solutions. Everything from evacuation planning to potential mitigation efforts can be included, and the effort of bringing many different stakeholders together helps to aid future coordination and discussion on mitigating
Future Opportunities for Science and the Profession
The understanding of wildfires and how they ignite and spread within our communities is improving, but there are still many unanswered questions. Embers are the key mechanisms of spread from wildfires into communities, but much of this understanding is in its infancy.We understand vulnerabilities for individual structures, but have a hard time quantifying just how impactful one measure will be versus another. From sprinklers to home spacing, we struggle to improve and quantify the best designs
There is opportunity to improve this knowledge via more detailed investigations of previous events and improved experiments and physical modeling of fire spread. This can be incorporated into a risk-informed framework to optimize future
decisions. A framework for wildfires focused on communities could help us make decisions on the most cost-effective measures and focus on reducing risk in an informed way. In our FPE community, increasing education on WUI design and outlining
these methods into a standardized, best-practice guide should be a near-term goal.
Transferring science to policy is an even bigger challenge. There are many questions here. How do we balance homeowner freedom to design their landscapes with fire safe strategies? What do we do about the huge stock of existing infrastructure?
How do we pay for the cost of initial improvements as well as continued maintenance? Again, fire protection engineers can play a critical role here. As they say, “knowledge is power,” and there is immense opportunity for fire protection
engineers to contribute to the analyses, which provide hard numbers to residents, policy makers, and insurance interests. Armed with numbers to support these mitigation efforts, hard options are easier to gain acceptance, similar to
the widespread adoption of fire sprinklers and other fire-safety codes and standards we have already helped champion.
Response is still important, but we fail to understand its influence in many ways. We often don’t know where a fire is until hours after it has wrought destruction on a community. There is a critical need for improved fire detection and
emergency communication, as well as tracking of firefighting resources, improving their safety. These can be coupled with improved modeling in data-assimilation called FIREFLY, using an ensemble-based data assimilation approach with the objective to forecast the location and speed of the fire. The specific focus of the present study is on evaluating the new features of FIREFLY at field scale
in a controlled grassland fire experiment known as FireFlux I. FIREFLY features the following components: an Eulerian front-tracking solver that treats the fire as a propagating front and uses Rothermel’s model for the rate of spread
(ROS, which is already used in weather modeling. Information must be put in the hands of decision makers quickly. From public information to critical evacuation alerts, how information is disseminated to the community, must be balanced
and understood before it’s widely implemented. Clearly, there are improvements to be made here, but we are learning some important lessons and already seeing improvements in the way evacuations are done far ahead of events in 2019.
Finally, ignition reduction should always be part of our efforts. It’s obvious we need to improve on this, especially from power transmission infrastructure; but let’s not forget that fires are going to start from accidents or arsonists
regardless of how much we improve our infrastructure. We must prepare our landscapes and communities for the future fires that will come.
MICHAEL J. GOLLNER, PhDis with the Department of Mechanical Engineering at the University of California, Berkeley.
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Sprinkler Hydraulics: A Guide to Fire System Hydraulic Calculations, 3rd edition
Updated by Russ Fleming, former president of the National Fire Sprinkler Association and past SFPE President and SFPE Fellow.
The Society of Fire Protection Engineers (SFPE) is a professional society for fire protection engineering established in 1950 and incorporated as an independent organization in 1971. It is the professional society representing those practicing the field of fire protection engineering. The Society has over 5,000 members and 100+ chapters, including many student chapters worldwide.