2.0 Methodology
2.1 Project Team
The RCI Project Team consisted of experts in the fields of fire behavior and suppression, forest and rangeland ecology, and geographic information systems (GIS). The RCI Project Team collaborated to complete a Community Risk/Hazard Assessment for each of the listed communities in Eureka County. The RCI Project Field Team included a Fire Specialists with extensive working wildland fire experience in Nevada and Resource Specialist experienced in the natural resource environment of the Great Basin.
The RCI Project Team used standardized procedures developed from the Draft Community Wildland Fire Assessment For Existing and Planned Wildland Residential Interface Developments in Nevada (Nevada’s Wildland Fire Agencies, Board of Fire Directors, April 2001; revised 2002). This approach incorporates values for fuel hazards, structural hazards, community design and preparedness, and fire protection capabilities into an overall community rating. A glossary of wildland fire terms frequently used in describing assessment results and recommendations is included in Appendix A.
2.2 Base Map Data Collection
The GIS Specialist on the RCI Project Team compiled and reviewed existing statewide geospatial data to create field maps for recording baseline data and data verification. Data sources for the maps were the Nevada Fire Safe Council, the Nevada Department of Transportation, the US Forest Service, and the Bureau of Land Management. Datasets and sources utilized are summarized in Table 2-1.
| Spatial Dataset | Data Source |
|---|---|
| Land Ownership | BLM Nevada State Office Mapping Services |
| Vegetation Communities | Nevada Gap Analysis Program Data, Utah Cooperative Fish and Wildlife Research Unit, Utah State University |
| Topography | US Geological Survey Digital Elevation Models and Topographic Maps |
| Fire Suppression Resources | Field Interviews |
| Roads | “TIGER” Census data (2000) University of Nevada Cooperative Extension - Eureka County Office |
| Current Aerial Photographs | US Geological Survey Digital Orthophoto Quadrangles (1994, 1996, or 1998) |
| Fuel Hazard Classes | BLM Nevada and Utah State Office Fire Hazard Potential Data |
| Fire History | BLM Nevada State Office Mapping Services US Forest Service Toiyabe Supervisor’s Office National Interagency Fire Center, Boise, Idaho University of Nevada Cooperative Extension - Eureka County Office |
2.2.1 Wildfire History
Recorded wildfire history was mapped using Bureau of Land Management and US Forest Service datasets and GIS databases that identify wildfire perimeters on federally managed lands for the last 24 years. Fire perimeters were mapped by agency personnel using global positioning system (GPS) data and screen digitizing on source maps with a minimum detail level of 1:250,000. The datasets have been updated at the BLM Nevada State Office and USFS Humboldt-Toiyabe Supervisor’s Office at the end of each fire season from information provided by each Nevada BLM Field Office and Humboldt-Toiyabe Ranger District. The datasets are intended to be central sources of historical GIS fire data used for fire management and land use planning on federal lands.
In addition to the fire perimeter information, point data for all fire ignitions within Nevada from 1980 to 2003 was obtained from the National Interagency Fire Center (NIFC) database in Boise, Idaho. This dataset includes an ignition point coordinate and an acreage component as reported to NIFC through a variety of agencies. This data is summarized in Table 3-2 and provides the ignition point locations for the maps in this report. In many cases, the ignition point location is only accurate to within the section; in such cases, the point coordinate is located in the section center on the maps.
The wildfire history and ignition history data were used to formulate risk ratings and develop recommendations specific to areas that have been repeatedly impacted by wildland fires. Observations made from the RCI Project Team and comments from local fire agencies were used to develop recommendations in areas without recent wildfire activity where accumulations of fuels or expansion of urban development into the interface area represents a growing risk.
2.3 Community Risk/Hazard Assessment
The wildland-urban interface is the place where homes and wildland meet. This project focused on identifying risks and hazards in the wildland-urban interface areas countywide by assessing each community individually. Site-specific information for each community was collected during field visits in Eureka County conducted on July 26 and 27, 2004. The predominant conditions recorded during these site visits were used as the basis for the Community Risk/Hazard Assessment ratings.
2.3.1 Ignition Risk Assessment Criteria
Fire Specialists on the RCI Project Team assigned an ignition risk rating of low, moderate, or high for each community assessed. This rating was based on four sources of information: the historical record of ignition patterns and fire polygons provided by the National Interagency Fire Center, Bureau of Land Management, and US Forest Service databases, interviews with local fire department personnel and local Fire Management Officers, field visits to each community, and the professional judgment of the RCI Fire Specialists based on their experience with wildland fire ignitions in Nevada.
2.3.2 Hazard Assessment Criteria
The Community Risk/Hazard Assessments were completed using methodology outlined in the Draft Community Wildland Fire Assessment For Existing and Planned Wildland Residential Interface Developments in Nevada (Nevada’s Wildland Fire Agencies 2001, revised 2002). This system assigns hazard ratings of low through extreme based on the scoring system shown in Table 2-2 and detailed in Appendix B.
| Hazard Category | Score |
|---|---|
| Low Hazard | < 41 |
| Moderate Hazard | 41-60 |
| High Hazard | 61-75 |
| Extreme Hazard | 76+ |
To arrive at a score for the community, five primary factors that affect potential fire hazard are assessed: community design, construction materials, defensible space, availability and capability of fire suppression resources, and physical conditions such as fuel loading and topography. A description of each of these factors and their importance in developing the overall score for the community is provided below. Individual community score sheets are provided at the end of each community assessment.
Community Design
Aspects of community design account for 26 percent of the total assessment score. Many aspects of community design can be modified to make a community more fire safe. Factors considered include:
- Interface Condition. Community safety is affected by the density and distribution of structures with respect to the surrounding wildland environment. Four condition classes are used to categorize the wildland-urban interface: Classic, Intermix, Occluded, and Rural. Definitions for each interface condition are included in the glossary of wildland fire terms in Appendix A.
- Access. Design aspects of roadways influence the hazard rating assigned to a community. A road gradient of greater than five percent can increase response times for heavy vehicles carrying water. Roads less than twenty feet in width often impede two-way movement of vehicles and fire suppression equipment. Hairpin turns and cul-de-sacs with radii of less than 45 feet can cause problems for equipment mobility. Adequately designed secondary access routes and loop roads in a community can lower a hazard rating. Visible, fire-resistant street and address identification and adequate driveway widths also reduce the overall community hazard rating.
- Utilities. Poorly maintained overhead power lines can be a potential ignition source for wildfires. It is important to keep power line corridors clear of flammable vegetation, especially around power poles and beneath transformers, as fires have been known to start from arcing power lines during windy conditions. Keeping flammable vegetation cleared from beneath power lines and around power poles reduces potential hazards from damaged power lines. Energized power lines may fall and create additional hazards for residents and firefighters, including blocked road access. Power failures are especially dangerous to a community without a backup energy source. Many communities rely on electric pumps to provide water to residents and firefighters for structure protection and fire suppression.
Construction Materials
The type of materials used for construction account for sixteen percent of the total assessment score. While it is not feasible to expect all structures in the wildland-urban-interface area to be rebuilt with non-combustible materials, there are steps that can be taken to address specific elements that affect structure ignition potential in the interface area. Factors considered in the assessment include:
- Building Materials. The composition of building materials determines the length of time a structure could withstand high temperatures before ignition occurs. Houses composed of weathered wood siding and wood shake roofing are usually the most susceptible to ignitions. Homes constructed of medium density fiberboard (MDF) siding are typically considered ignition resistant. MDF siding burns when exposed to high temperatures for a prolonged period of time. Buildings with stucco exteriors also can withstand high temperatures. Houses with tile, metal, or composition roofing are able to withstand high temperatures and long durations of heat exposure.
- Architectural Features. Unenclosed balconies, decks, porches, attic vents, or eaves on homes provide areas where sparks and embers can be trapped, smolder, ignite, and rapidly spreading fire to the house. A high number of houses within the wildland-urban-interface area with these features implies a greater risk to the community.
Defensible Space
Defensible space accounts for sixteen percent of the assessment score. The density and type of fuels around a home determine the potential fire exposure for damage to the home. A greater volume of trees, shrubs, dry weeds, dry grass, woodpiles, and other combustible materials near the home will ignite more readily, produce more intense heat during a fire, and increase the threat of property damage or loss. Defensible space is one of the factors that homeowners can easily manipulate in order to improve the chances that a home or other property avoids damage or complete loss from a wildfire.
Suppression Capabilities
The availability and capability of fire suppression resources account for sixteen percent of the total assessment score. Knowledge of the capabilities or limitations of the fire suppression resources in a community can help the residents take action to maximize the resources available. Factors considered in the assessment include:
- Availability, Quantity, and Training Level of Firefighting Personnel When a fire begins in or near a community, having the appropriate firefighting personnel available to respond quickly is critical to saving structures. Whether there is a local paid fire department, volunteer department, or no local fire department impacts how long it takes for firefighting personnel to respond to a reported wildland fire or to a threatened community.
- Quantity and Type of Fire Suppression Equipment. The quantity and type of available fire suppression equipment has an important role in minimizing the effect of a wildfire on a community. Effective wildland firefighting requires specialized equipment.
- Water Resources. The availability and location of water resources is critical to fighting a wildland fire. Whether there is a community water system with adequate flow capabilities, or whether firefighters must rely on local ponds or other drafting sites affects how difficult it will be for firefighters to protect the community.
Physical Conditions
The physical conditions that influence fire behavior account for 26 percent of the hazard rating. Physical conditions include slope, aspect, topography, fuel type, and fuel density. With the exception of changes to the fuel composition, the physical conditions in and around a community cannot be altered to make the community more fire safe. Therefore, an understanding of how these physical conditions can influence the fire behavior is essential to planning effective preparedness activities such as fuel reduction treatments. Physical conditions considered in the assessment include:
- Slope, Aspect, and Topography. In addition to local weather conditions, slope, aspect, and topographic features are also used to predict fire behavior. Steep slopes greatly influence fire behavior. Fire usually burns upslope with greater speed and longer flame lengths than on flat areas. Fire will burn downslope; however it usually burns downhill at a slower rate and with shorter flame lengths than in upslope burns. East aspect slopes in the Great Basin may experience afternoon downslope winds that can rapidly push fires down slope. West and south facing aspects are subject to more intense solar exposure, which preheats vegetation and lowers the moisture content of fuels. Canyons, ravines, and saddles are topographic features that are prone to higher wind speeds than adjacent areas. Fires pushed by winds grow at an accelerated rate compared to fires burning in non-windy conditions. Homes built mid-slope, at the crest of slopes, or in saddles are most at risk due to wind-prone topography in the event of a wildfire.
- Fuel Type and Density. Vegetation type, fuel moisture values, and fuel density around a community affect the potential fire behavior. Areas with dense, continuous, vegetative fuels carry a higher hazard rating than communities situated in areas of irrigated, sparse, or non-continuous fuels. Several consecutive years of above normal precipitation will result in excessive cheatgrass growth and ground litter. These conditions in combination with hot and dry weather, steep slopes, or high winds can create a situation in which the worst-case fire severity scenario can occur.
2.3.3 Hazard Mapping
Fuel hazard maps were initially generated by the BLM (Nevada and Utah State Offices) using wildfire hazard delineations derived from vegetation data (Nevada GAP Analysis Program satellite dataset at thirty-meter resolution). A total of 65 vegetation types were mapped statewide and reclassified into four wildfire hazard categories (low, moderate, high, extreme) based on anticipated fire behavior for each vegetation cover type. For example, pinyon-juniper cover types were generally rated as extreme fuel hazards, while sparse shadscale cover types were rated as low hazards.
The RCI Project Team visited the high and extreme hazard communities and verified the BLM hazard information by comparing the hazard ratings on the existing fuel hazard map to vegetation, slope, and aspect conditions directly observed in the field. Where necessary, changes to the ratings were drawn on the maps and used to update the wildfire hazard potential layer of the project database. Photo points were established in high and extreme fuel hazard communities to monitor future changes in the fuel hazard conditions. Fuel hazard mapping was completed and figures prepared for all communities with high or extreme community hazard ratings. Photos of representative fuel types in Eureka County are included in Appendix C.
2.3.4 Fire Behavior Worst-Case Scenario
Fire Specialists on the RCI Project Team described a worst-case wildfire scenario for each community based on the analyses of the severe fire behavior that could occur given a set of weather conditions, observed fuel load conditions, and minimal fire suppression resources. The worst-case scenario does not describe the most likely outcome of a wildfire event in the interface, but illustrates the potential for damage if a given set of conditions were to occur simultaneously. The worst-case scenarios are described in this document for public education purposes and are part of the basis for the fuel reduction recommendations.
2.4 Interviews with Fire Personnel
The RCI Project Team interviewed local fire department personnel and regional agency Fire Management Officers to obtain information on wildfire training, emergency response time, personnel and equipment availability, evacuation plans, pre-attack plans, and estimates of possible worst-case scenarios. Local fire personnel reviewed maps showing the history of wildfires to ensure that local information on wildland fires was added to the datasets when possible. A list of fire agency personnel contacted for information used in the assessments is included in Appendix D.
2.5 Recommendation Development
A wide variety of treatments and alternative measures can be used to reduce ignition risks, mitigate fire hazards, and promote fire safe communities. Proposed recommendations typically include physical removal or reduction of flammable vegetation, increased community awareness of the risk of fires and how to reduce those risks, and coordination among fire suppression agencies to optimize efforts and resources. The RCI Project Team met repeatedly to analyze community risks, treatment alternatives, and treatment benefits. Treatment recommendations to reduce existing risks and hazards were formulated based upon professional experience, the hazard assessment results, and information developed inconjunction with the “Living With Fire” publications, National Fire Plan, and FIREWISE resources (National Fire Plan website: www.fireplan.gov/reports/7-19-en.pdf; FIREWISE website: www.firewise.org; and Nevada Cooperative Extension publications). The recommendations included in this report are considered high priorities for individual communities and are presented in a relative order of importance.