2.0 Methodology
2.1 Project Team
The RCI Project Team was composed of experts in the fields of fire behavior and suppression, geographic information systems (GIS), natural resource ecology, and forest health who collaborated to complete a Community Risk/Hazard Assessment for each community. The RCI Project Team included personnel with extensive wildland fire prevention and suppression experience in Nevada and site specific experience in the natural resource environment of the Great Basin.
The RCI Project Team used standardized procedures developed in accordance with 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 hazardous fuels and landscape features, hazardous structural features, community design, and fire protection capabilities into an overall community rating.
2.2 Base Map Data Collection
Geographic Information System Specialists 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 included the Nevada Fire Safe Council, the Nevada Department of Transportation, the NRCS, the Bureau of Land Management and the US Forest Service. 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 and Telephone Interviews |
| Roads | Nevada Department of Transportation “TIGER” Census data (2000) |
| Current Aerial Photographs | US Geological Survey Digital Orthophoto Quadrangles (1994, 1996, or 1998) |
| Fuel Hazard Conditions | BLM Nevada State Office Fire Hazard Potential Data |
| Fire History | BLM Nevada State Office Mapping Services US Forest Service Humboldt-Toiyabe Supervisor’s Office National Interagency Fire Center, Boise Idaho |
2.2.1 Wildfire History
Wildfire history information was mapped using Bureau of Land Management and US Forest Service datasets and GIS databases that identify wildfire perimeters on federally managed lands from 1980 to 2003. This information was compiled by agency personnel using a global positioning system (GPS) and screen digitizing from source maps with a minimum detail level of 1:250,000. The dataset is updated at the BLM Nevada State Office and 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 Districts. The datasets are the central source of historical GIS fire data used to support fire management and land use planning on federal lands.
During interviews with local fire experts, the RCI Project Team may have identified fire perimeters that were not included in BLM or USFS datasets. Fires that occurred on private land are generally recorded on paper maps and have not been consistently included in Federal agency GIS datasets. Fire locations identified during interviews with local fire personnel were recorded on field maps (where possible) and were added to the project wildfire perimeter dataset.
In addition to fire perimeter information, point data for fire ignitions in 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. These data, summarized in Table 3-2, provide the ignition point locations presented in this report. In many cases, the ignition point location is accurate only to the section. In such cases, the point coordinate is mapped in the center of the section.
The wildfire history and ignition history data were used to formulate ignition risk ratings and to develop recommendations specific to areas repeatedly impacted by wildland fires. Observations made by the RCI Project Team and comments from local fire agencies were used to develop recommendations for areas that lack recent wildfire activity where accumulations of fuels or an 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 hazards and risks in the wildland-urban interface areas by assessing each community individually. Site-specific information for each community was collected during field visits in Lander County conducted May 17 through May 19, 2004. The predominant conditions recorded during these site visits served as the basis for development of Community Risk and Hazard Assessment ratings.
2.3.1 Ignition Risk Assessment Criteria
The Fire Specialist on the RCI Project Team assigned an ignition risk rating of low, moderate, or high to each community assessed. This rating is based four sources of information:
- Interpretation of the historical record of ignition patterns and fire polygons provided by the National Interagency Fire Center, Bureau of Land Management databases, and US Forest Service databases.
- Interviews with local fire department personnel and local area Fire Management Officers.
- Field visits to each community.
- 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 the methodology outlined in the Draft Community Wildland Fire Assessment For Existing and Planned Wildland Residential Interface Developments in Nevada. This system assigns hazard ratings of low through extreme based on the scoring system shown in Table 2-2.
| Hazard Category | Score |
|---|---|
| Low Hazard | < 41 |
| Moderate Hazard | 41-60 |
| High Hazard | 61-75 |
| Extreme Hazard | 76+ |
To arrive at a score for a community, five primary factors affecting potential fire hazard were assessed: community design, construction materials, defensible space, availability and capability of fire suppression resources, and physical conditions such as fuel loading and topography. A glossary of wildland fire terms is provided in Appendix A. A description of each factor and their importance in developing the overall score for a community is provided below. The point distribution for each factor is provided in Appendix B. A table is provided at the end of each community chapter that presents the point value assigned to each hazard assessment element.
Community Design
Aspects of community design account for 26 percent of the total assessment score. Many aspects of community design can be modified to improve community fire safety. Factors considered include:
- Interface Condition Community safety is affected by the density and distribution of structures with respect to the surrounding wildland environment. Four situations are recognized and used to categorize the wildland-urban interface: Classic Interface, Intermix, Occluded, and Rural. Definitions for each Condition Class are provided 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 20 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 wildfire ignition source. It is important to keep power line corridors clear of flammable vegetation, 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 citizens and firefighters, including blocked road access. Power failures are especially dangerous if a community lacks backup sources for electrical power. Many communities rely on electric pumps to provide water to residents and firefighters for structure protection and fire suppression.
Construction Materials
Sixteen percent of the total assessment score is attributed to construction materials. 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 reduce risks associated with hazardous construction in the interface area. Factors considered in this assessment include:
- Building Materials. The composition of building materials determines the length of time a structure can withstand high temperatures before ignition occurs. Houses composed of weathered wood siding and wood shake roofing are usually the most susceptible to ignition. Homes constructed with medium density fiberboard (MDF) siding are typically considered fire resistant. MDF siding burns only when exposed to high heat for a significant amount of time. Buildings that have 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 or unscreened balconies, decks, porches, attic vents, and eaves on homes provide areas where sparks and embers can be trapped, smolder, and ignite, rapidly spreading fire to the home. A high number of houses within a wildland-urban interface 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 levels to the home. A greater volume of trees, shrubs, dry weeds, dry grass, woodpiles, and other combustible materials near the home will produce more intense heat during a fire, and increase the threat of damage or loss of the home. Defensible space is one of the most manageable factors in improving the chance that a home or other property will avoid being damaged or lost in a wildfire.
Suppression Capabilities
Suppression capabilities accounts 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 and lives. Whether there is a local paid fire department, volunteer department, or no local fire department impacts how long it will take for firefighting personnel to respond to a wildfire.
- Quantity and Type of Fire Suppression Equipment. The quantity and type of fire suppression equipment available has an important role in minimizing the effect of wildfire on a community. Effective wildland firefighting requires specialized equipment not commonly kept in urban fire departments.
- Water Resources. The availability of water resources is critical to fighting a wildland fire. The nature of the water resources available (for example, a community water system with adequate fire flow capabilities versus local ponds or other drafting sites) will affect how easy or difficult it will be for firefighters to protect the community.
Physical Conditions
Physical conditions accounts for 26 percent of the assessment score. Fire behavior is influenced by numerous physical conditions and is dynamic throughout the life of the fire. With the exception of changes to fuel types and density, the physical conditions in and around a community cannot be altered to make the community more fire safe. An understanding of how these physical conditions can influence fire behavior is essential to planning effective preparedness measures, such as fuel reduction treatments. Physical conditions considered in this assessment include:
- Slope, Aspect, and Topography. Slope, aspect, and topographic features are 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 but it usually does so at a slower rate and with shorter flame lengths than in upslope burns. East aspect slopes in the Great Basin may experience downslope winds in the afternoon. These winds may rapidly increase downhill burn rates. 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. Because the surrounding topography is more wind-prone, homes built mid-slope, at the crest of slopes, or in saddles are more at risk in the event of a wildfire.
- Fuel Type and Density. Vegetation types, fuel moisture values, and fuel densities around a community affect potential fire behavior. Areas with dense, continuous, vegetative fuels carry a higher hazard rating than communities in areas of irrigated, sparse, or non-continuous fuels. Hot and dry weather conditions, or years with above normal precipitation and cheatgrass production in combination with steep slopes or high winds can create situations in which the worst-case fire severity scenario can occur. Photographs of representative fuel types in Lander County interface areas are provided in Appendix C.
2.3.3 Fuel Hazard Mapping
Fuel hazard maps were initially prepared by the BLM (Nevada and Utah State Offices) using wildfire hazard delineations derived from vegetation data (Nevada GAP Analysis Program satellite dataset at 30-meter resolution). A total of 65 vegetation cover types were mapped statewide and reclassified into four wildfire hazard categories (low, moderate, high, and extreme) based on anticipated fire behavior. For example, pinyon-juniper cover types were generally rated as having an extreme fuel hazard, while sparse salt desert shrub cover types were rated as having a low fuel hazards.
The RCI Project Teams visited high and extreme fuel hazard communities and verified the BLM hazard information by comparing the hazard ratings on the existing fuel hazard map to observed vegetation, slope, and aspect conditions. Where necessary, changes to the ratings were drawn on maps and used to update the wildfire hazard potential layer of the project database. Photo points were established in high and extreme fuel hazard areas to monitor future changes in fuel hazard conditions. Hazard mapping was reviewed for the listed Lander County communities. In this report hazard maps are provided only for those communities where high and extreme fuel types were noted. These include Austin, Grass Valley, and Kingston.
2.3.4 Fire Behavior Worst-Case Scenario
RCI Project Team Fire Specialists developed worst-case wildfire scenarios based on their analysis of the severe fire behavior that could occur given a set of weather conditions, observed fuel load conditions, and minimal fire suppression resources. These scenarios describe a maximum potential for loss of property and, in some cases, human lives. The worst-case scenario does not describe the most likely outcome of a wildfire in the interface but it illustrates the potential for damage if a given set of conditions were to occur simultaneously. The worst-case scenarios were developed to serve two purposes: to assist in public education efforts and to be considered during development of fuel reduction recommendations.
2.4 Interviews with Fire Personnel
The RCI Project Team interviewed local fire department personnel and local 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 included. Refer to Appendix D for a list of persons contacted.
2.5 Recommendation Development
A wide variety of treatments and alternative measures can be used to reduce ignition risks, to mitigate fire hazards, and to promote fire safe communities. Proposed recommendations typically include the 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 were formulated based on professional experience, quantitative hazard assessment, and information developed in conjunction with the National Fire Plan, FIREWISE resources, and University of Nevada Cooperative Extension publications. (A comprehensive listing of references used in the compilation of this report is given in Section 16.0.) The recommendations included in this report are considered high priorities for individual communities and are presented in a relative order of importance.