RCI ReportsMineral County Fire Plan

2.0 Methodology

2.1 Project Team

A project team including experts in the fields of fire behavior and suppression, geographic information systems (GIS), natural resource ecology, and forest health collaborated to complete a Community Risk/Hazard Assessment for each community. Teams include personnel with extensive working wildland fire experience in Nevada and resource specialists experienced in the natural resource environment of the Great Basin.

The teams used standardized procedures developed from the Draft Community Wildland Fire Assessment For Existing and Planned Wildland Residential Interface Developments in Nevada during the assessment process (Nevada’s Wildland Fire Agencies, Board of Fire Directors, April 2001; revised 2002). This approach incorporates values for fuel hazards, structural hazards, community preparedness, and fire protection capabilities into an overall community rating.

A glossary of terms is included in Appendix A.

The project geographic information specialists compiled and reviewed existing statewide geospatial data to provide the assessment teams with maps for use and verification in the field. Data sources for the maps were the Nevada Fire Safe Council, the Nevada Department of Transportation, the Natural Resource Conservation Service, the US Forest Service, and the Bureau of Land Management. Datasets and sources utilized include:

  • Land ownership - USDOI-BLM Nevada State Office Mapping Services
  • Vegetation communities - Nevada Gap Analysis Program Data, Utah Cooperative Fish and Wildlife Research Unit, at Utah State University
  • Topography - USGS Digital Elevation Models and Topographic Maps
  • Fire suppression equipment and personnel - Field Interviews
  • Roads - TIGER Census data (2000)
  • Current aerial photographs - USGS Digital Orthophoto Quadrangles (1994, 1996, or 1998)
  • Soil surveys - USDOI-BLM Nevada State Office Mapping Services USDA-NRCS SUURGO Website
  • Fuel types - USDOI-BLM Utah State Office Fire Hazard Potential Data
  • Fire History - USDOI-BLM Nevada State Office Mapping Services, USDA-USFS Nevada State Office Field Interviews

Existing data were reviewed and pertinent information compiled on maps in geographic information system (GIS) format and then field verified during the data collection phase of the Community Risk/Hazard assessments. Geographic information system specialists provided the data management for the effective and accurate analysis of the statewide geospatial data, and the production of the maps in this report.

2.1.1 Wildfire History

Wildfire history information is represented spatially using polygon datasets obtained from BLM and USFS GIS databases that locate wildfire perimeters on federally managed lands over the past 21 years. Fire perimeters were mapped by agency personnel using GPS and screen digitizing on source maps with a minimum detail level of 1:250,000. This dataset is re-compiled at the Nevada BLM state office at the end of each fire season from information provided by all of the Nevada BLM field offices. The dataset is intended to be a central source of historical GIS fire data to support fire management efforts and land use planning on federal lands.

As a result of interviews with local fire experts, the project teams identified additional fire perimeters not present in the BLM and USFS datasets. Fires that occur on private lands are generally recorded on paper maps only and are not consistently included in the federal agencies’ GIS datasets. Fire histories recovered through the interview process were drawn on the field maps where possible and then screen digitized into the project wildfire perimeter dataset.

In addition to the fire perimeter (polygon) information obtained at the state level, point data for all fire ignitions within Nevada from 1980 to 2003 was obtained through the National Interagency Fire Center (NIFC) database in Boise, Idaho. This dataset includes an ignition point coordinate and an acreage component as reported to the NIFC through a variety of agencies and forms the base for the wildfire history table presented in Section 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 maps.

The fire history data and ignition patterns were used to formulate risk ratings and to develop recommendations specific to areas that have been repeatedly impacted by wildland fires. Observations made from the project team members and comments from local fire agencies also allowed for the development of recommendations for areas absent of recent wildfire activity where a significant buildup of fuels or expansion of urban development into the interface area represents a growing risk.

2.2 Community Risk/Hazard Assessment

The wildland-urban interface is the place where homes and wildland meet. This project focuses 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 conducted between January 19 and January 23, 2004. The predominant conditions recorded during these site visits were used as the basis for the Community Risk and Hazard Assessment ratings.

2.2.1 Ignition Risk Assessment Criteria

The Project Team Fire Specialists assigned ignition risk ratings of low, moderate, or high for each community assessed. This rating is based on interpretation of the historical record of ignition patterns and fire polygons provided by NIFC, BLM, and USFS databases, interviews with local fire department personnel and regional Fire Management Officers, field visits to each community, and the studied judgment of the fire specialists based on their professional experience with wildland fire ignitions in the state of Nevada.

2.2.2 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. This system assigns hazard ratings of low through extreme based on the following scoring system:

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, four primary factors that affect potential fire hazard are assessed: community design, structure survivability, availability of fire suppression resources, and physical conditions such as fuel loading and topography. A description of each of these factors and the importance in developing the overall score for the community is provided below. Summary tables presenting the point values assigned to each element in the wildfire hazard assessment are provided at the end of each community-specific section. Photographs of representative fuel types for each community are provided in Appendix B.

Community Design

Community design accounts for 26 percent of the total score of the hazard assessment. Many aspects of community design can be modified to make a community more fire safe. Factors considered include:

  • Interface Condition Describes the density and distribution of structures with respect to the surrounding wildland environment. The four Interface Condition Classes are: Classic, Intermix, Occluded, and Rural. Definitions for each Condition Class are included in the glossary (Appendix A).
  • Access. Design aspects of roadways influence the hazard rating assigned to a community. A road gradient of greater than 5 percent can imply increased response times for 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. The presence of secondary entrances and exits and loop roads in a community can lower a hazard rating.
    In addition, visible, fire-resistant street and address identification and adequate driveway widths are aspects of access infrastructure that also influence the hazard rating of a community.
  • 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 additional hazards that fires and electric utilities present. Damage by fire to power lines often creates power failures, which are especially dangerous to a community without a backup energy source, as most communities rely on electric pumps to provide water to residents and firefighters for structure protection and fire suppression. Energized power lines may fall and create additional hazards for citizens and firefighters, including blocked road access. Properly maintained vegetation within power line corridors greatly reduces these potential hazards, and the risk of additional ignitions, along those easements.

Construction Materials

Construction materials account for 31 percent of the total score of the hazard assessment. 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 the hazards associated with construction in the interface area. Factors considered in the assessment include:

  • Structure Building Materials. The composition of building materials determines the length of time a structure could withstand high temperatures before ignition occurs. Houses composed of wood siding and wood shake roofing are usually the most susceptible to ignitions. Houses built with stucco exteriors and tile, metal or composition roofing are able to withstand much higher temperatures and heat durations, and thereby present a much lower ignition risk from firebrands and proximity to advancing flames.
  • Architectural Features. Unenclosed balconies, decks, porches, or eaves on homes provide areas where sparks and embers can smolder and create drafts that rapidly spread fire if the house ignites. A high number of houses within a wildland-urban interface with these features implies a greater hazard to the community.

Defensible Space

Density and type of fuel around a home determines the potential fire exposure levels to the home. A greater mass of trees, shrubs, dry weeds and grass, woodpiles, and other combustible materials near the home will produce more intense heat during a fire, increasing the threat of losing the home.

Suppression Capabilities

Suppression capabilities account for 16 percent of the total score for the assessment. 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 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 and address the threat that it presents to homes and people.
  • 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. Wildland firefighting requires specialized equipment.
  • Water Resources. The availability of water resources is critical to fighting a wildland fire. Whether there is a community water system with adequate fire flow capabilities, or whether firefighters must rely on local ponds or other drafting sites may indicate whether firefighters will be able to adequately protect the community.

Physical Conditions

Physical conditions account for 27 percent of the assessment. Fire behavior is influenced by numerous physical conditions and is dynamic throughout the life of the fire. With the exception of changes to the fuel type and fuel 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 influence the behavior of a fire is essential to planning effective presuppression activities, such as fuel reduction treatments. Physical conditions considered in the assessment include:

  • Typical Weather Conditions. The time of day and weather conditions during the fire including temperature, relative humidity, wind speed and direction contribute to the actual fire behavior (Campbell, 1991).
  • Slope, Aspect and Topographical Variations. In addition to local weather conditions, slope, aspect, and topographical variations can be used to predict fire behavior. West and south facing aspects are most prone to severe fire behavior due to preheated vegetation that has lower moisture content from daylong sun exposure. Steep slopes greatly influence fire behavior. Fire usually burns upslope with greater speed and 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. Canyons, ravines, and saddles are topographical features that are prone to higher wind speeds than adjacent areas. Homes built mid-slope, at the crest of slopes or in saddles are located in areas of higher hazard due to topography.
  • Fuel Type and Density. Vegetation type and density around a community affect the potential fire behavior. Areas with thick, continuous, vegetation fuels present more hazardous conditions than communities situated in areas of mosaic or broken fuels. Weather conditions that dry the vegetation in combination with steep slopes or high winds can create situations in which the worst-case fire severity scenario can occur.

2.2.3 Hazard Mapping

Initial wildfire hazard maps were generated using wildfire hazard delineations derived by the Nevada and Utah BLM from vegetation type data provided by the Nevada Gap Analysis Program dataset, which identifies vegetation types derived from satellite data. Land cover for the entire state was classified into one of 65 vegetation types at a resolution of 30 meters, then the BLM fire specialist team reclassified the vegetation types into wildfire hazard potentials based on the hazard for that particular cover type. For example, pinyon-juniper cover types may be rated as extreme, while low sagebrush cover types would be rated low.

Once the hazard mapping was completed, field teams visited the selected communities and verified the BLM hazard information by comparing the hazard ratings on the existing fuel hazard map to the vegetation conditions directly observed in the field. Where necessary, changes to the ratings were drawn on the maps and GIS specialists then updated these changes in the wildfire hazard potential layer in the project database.

2.2.4 Fire Behavior Worst-Case Scenario

The worst-case scenarios described in this document are based on the project wildfire specialists’ estimation of severe fire behavior that could occur given a set of weather conditions, observed fuel loading conditions, and minimum 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 event at 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.

2.3 Interviews with Fire Personnel

The 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 included. Refer to Appendix C for a list of persons contacted.

2.4 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 how to reduce the risk of fire ignitions and mitigate fire hazards, and coordination among fire suppression agencies to optimize efforts and resources. The project team met repeatedly to analyze community risk factors, treatment alternatives, and treatment benefits. Treatment recommendations were formulated based upon professional experience, quantitative hazard assessment, and information developed in conjunction with the National Fire Plan, FIREWISE resources, and Nevada Cooperative Extension publications. (See Section 12.0 for a comprehensive listing of references used in the compilation of this report.)