Wildfires pose a risk to the fabric of rural communities and essential forest resources such as timber, water, habitat, and ecological services. Wildfire risk assessment models are used to provide guidance for community members and forest managers as they plan and implement changes to reduce the risk of loss due to wildfire. The actions necessary to provide this mitigation are usually fuel reduction treatments, which vary greatly in effectiveness, cost, and impact to ecological processes. In addition to assessing fire risk, sometimes models are designed to measure the effectiveness of these fuel treatments in order to direct policy. The three purposes of this study are to provide an assessment of the current fire risk in the rural community of Forest Ranch, California, to test three techniques for identifying optimum locations for fuel treatments, and to measure the modeled effectiveness of these fuel treatment locations in reducing fire risk.
Wildfire plays a natural and integral role in many ecosystems throughout the world. Although humans are the most common source of wildfires in the United States today, vegetation and entire ecosystems evolved to adapt to the influence of wildfires ignited by natural sources. Anthropogenic use and/or control of fire contribute to the frequency and intensity of wildfires regardless of the source, thereby affecting the landscape composition and leading to feedback loops. In California, Native Americans utilized fire as a tool for increasing beneficial natural resources and preserving negative feedback loops. This anthropogenic burning, in combination with naturally occurring fires, has produced a landscape that both requires and prospers from fire. Without fire, fuels accumulate, leading to a landscape prone to high intensity fires, and potentially leading to a shift in fire regime. While fire-dependent landscapes would benefit from allowing the natural fire process to occur without human influence, we have interjected our lives into the system. Local communities, land managers and multiple levels of government policy require active management of the landscape to control the fire regime, primarily through fire suppression and fuel treatments. In the case of the Forest Ranch community, and the needs of local residents and the timber industry, the desired fuel condition would be a situation with low likelihood of supporting high severity crown fire over spatially broad areas. Assessing the fuel loading and composition of a landscape helps to identify locations that require rearrangement of fuels in order to prevent high severity fires from occurring.
While California’s landscapes have evolved with fire, they have not adapted to recent changes in human needs. As European settlers began to populate the forested mountains of California, they chose to suppress wildfire. The federal government supported this action, creating firefighting teams trained to extinguish any fire with the goal of growing timber for harvest. However, the forest and fuel load grew faster than the new stewards could actively manage; we are left with many landscapes in a precariously hazardous state. Many of California’s forests contain excessive fuel loadings and are primed for high intensity, stand-replacing fire behavior. While this is a significant problem for the balance of ecological health and ecosystem services, it is also a serious hazard for the humans who have chosen to make their homes in the forest.
During the past century communities have expanded their influence within the fire-prone forests of California, creating a volatile mix of humans and nature that has evolved without true consideration of risks. Every year wildfires destroy hundreds of homes, despite the fire-fighting infrastructure and abundant fuel treatments that have been completed to prevent or minimize loss to fire. Millions of dollars are spent annually on these fuel treatments; it should be known which treatments are the most effective. When lives, property, aesthetic value, and forest resources are at stake, extensive fire suppression measures should be taken. However, if valuable and limited resources are being focused toward inefficient or ineffective priorities, potential losses to fire will not be minimized. Assessing a reduction in fire risk as a result of fuel treatments is not a simple matter of measuring biomass removed from a site. However, the risk reduction can be evaluated and assessed for efficiency with the use of a computer-based model. Geographical information systems (GIS) and remote sensing are two powerful tools that can be combined with field observations to develop a model for accurately assessing the fire risk of a community, and for assessing the numerous costs and benefits of different fuel treatments. This study utilizes data that was derived by modeling fire behavior to assess the level of fire risk in Forest Ranch, CA. It results in quantitative and qualitative outputs that are used to compare spatial configurations of fuel treatments. Additionally, visual presentations of the analysis of the resulting data can be used to educate communities of their potential fire risk.
Over the past few hundred years fire in California has transitioned from an anthropogenic tool to a threatening hazard. To evaluate how fire has become a natural hazard requires proper definition of hazard. A hazard is defined as a natural process that has the potential to negatively impact human resources. Hardy specifically defines fire hazard as being an arrangement of fuels with sufficient volume, type, and condition that increase probability of fuel ignition and result in fires that are beyond the limits of standard suppression efforts. Implicit in this definition of fire hazard is that humans desire suppression in the first place. In essentially all cases the goal of fire suppression is to protect lives, high-value property and forest resources. With humans continuing to populate wildlands, protecting human lives and property has become a priority. This has led to increasingly aggressive attacks upon the wildfires. The use of fire suppression as a tactic for reducing fire hazards is counterproductive because it heightens the fire hazard while creating a major financial and ecological cost. Combustion has happened for millions of years; fire has occurred on California’s landscape for at least thousands of years and is an important and unavoidable component of the ecosystem. Due to the frequency of fire’s natural occurrence in northern California, every acre of fire that is suppressed is an acre of land still awaiting fire. The immediate benefit of suppressing the fire is well received by local residents and stakeholders, while the ever-increasing fuel load creates a higher fire-risk in following years. Diametrically opposed to fire suppression is promoting fire on the landscape. However, balancing the needs of growing populations and ecological needs by applying fire as a tool on the landscape is not simple due to the juxtaposition of human resources and fire-prone landscapes.
The wildland urban interface (WUI) is an area where residential development intermingles with undeveloped wildland vegetation. WUI is at the center of many human environment relationships, and the WUI may be the focus of loss of property by wildfire. It is at the WUI where wildland fires destroy most structures as a result of fuel buildup from decades of fire suppression and the presence of human-caused fire ignitions. The inevitability of fire within the WUI requires adequate preparation. Assessing the landscape and identifying specific locations with high fire risk conditions provides a baseline for planning fuel treatments that could minimize fire hazard.
Wildfires threaten homes and people within the WUI. However, those people and homes are threatening to forest ecosystems in which fire is an important process. Compounding the two-sided threat is that increased numbers of people in the WUI increase the problems related to emergency response (both suppression activities and evacuation protocols). Wildland fire fighters are requiring more and more structural firefighting skills as more homes are constructed in the WUI. This leads to a complex mixture of shared responsibilities, mutual aid agreements, and hierarchical “nightmares” of the incident command structure that often places agencies foreign to the local environment in greatest control of action. Along with these shared responsibilities comes the need to answer questions regarding which goals receive highest priority in the firefighting actions.
Fire is the result of three physical components— heat, oxygen, and fuel. Fuel is considered to be any combustible material that is available to fire. Fuel types vary considerably in the ability to combust based on their chemical composition and spatial arrangement. Fuels that are continuously distributed on a landscape are able to carry fire directly from one area to another. Fuels that are distributed in a complex pattern, including patches with little or no available fuel, cause fire to move more sporadically. Although the chemical composition of fuels cannot be readily altered as a method of fire suppression, vegetation that is more volatile (containing chemicals that readily burn at high intensity) can be replaced with vegetation that is less volatile. Although this is possible surrounding homes, it is clearly not an option for forest ecosystems. However, the structure of fuels can be altered in a process referred to as a “fuel treatment.” Methods of fuel treatment vary greatly by cost, effectiveness, and impact to the surrounding ecosystem. A number of fuel treatment methods, including brush clearing, selective timber thinning, mastication, or prescribed burning, are commonly conducted to minimize negative impacts and labor costs while maximizing risk reduction.
The purpose of this study is to test the efficacy of three different sets of fuel treatment locations for reducing fire risk at a range of spatial scales for Forest Ranch, a rural community in the coniferous forest at the junction of the Cascade and Sierra Nevada Ranges of Northern California. Fuel treatments occur across many types of landscapes, and share the consistent goal of reducing fire intensity and fire risk. In WUI areas, fire risk is a dominant management concern. As a result, finances are commonly focused on treatment methods for reducing fire risk, but limited funds are allocated for detailed analysis of the benefits of these treatments. This study will illuminate the best techniques for achieving the goal of reducing fire risk in the community of Forest Ranch, California, while also testing three techniques for identifying treatment locations.
This study is designed to address fire hazard reduction (more specifically, fire risk reduction, quantified by high intensity fire behavior) and to promote education of the homeowners about the current and potential fire risk. The fire risk assessment resulting from this study is a modeled surface and does not necessarily represent the actual conditions of the community. This uncertainty is the result of limitations in the model itself and the use of static data to represent dynamic fuel and vegetation conditions. Vegetation and fuel conditions were based on LANDFIRE data4 that was remotely sensed and field verified. Although the vegetation and fuels data has a 30-meter resolution, it is imported data that is based on environmental variables that may not represent the actual fuels and vegetation condition. However, using this readily available data allowed rapid completion of this study. Other communities, with limited budgets and personnel, can duplicate the methodology of this study to plan and manage their fuel treatments.