RCI ReportsDouglas County Fire Plan

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 a Fire Specialist with extensive wildland fire suppression and prevention experience in Nevada and a 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 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 design and preparedness, and fire protection capabilities into an overall community rating. A glossary of wildland fire terms used frequently in describing assessment results and recommendations is included in Appendix A.

2.2 Base Map Data Collection

The RCI Project Team Geographic Information System (GIS) Specialists 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.

Table 2-1. Primary Datasets and Sources Utilized in the Douglas County Community Wildfire Risk/Hazard Assessment.
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 Douglas County “MAGIC”
Roads Nevada Department of Transportation “TIGER” Census data (2000)
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
BLM Carson City Field Office
USFS Humboldt-Toiyabe Supervisor’s Office
National Interagency Fire Center - Boise, Idaho

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 administered lands during the past 24 years. Fire perimeters were mapped by agency personnel using Global Positioning System (GPS) data and screen digitizing from source maps with a minimum detail level of 1:250,000. The datasets have been updated at the Bureau of Land Management Nevada State Office and Humboldt-Toiyabe Supervisors Office at the end of each fire season from information provided by each BLM Field Office and Humboldt-Toiyabe Ranger District. The datasets are intended to be central sources of historical GIS fire data to support fire management efforts and land use planning on federal lands.

In addition to the fire perimeter information, point data for all recorded 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 included 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 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 to develop recommendations specific to areas that have been repeatedly impacted by wildland fires. Observations made by the RCI Project Team and comments from local fire agency personnel were used to develop recommendations in areas without recent wildfire activity where a significant buildup 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 hazards and risks 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 June 7 and June 17, 2004. The predominant conditions recorded during these site visits were used as the basis for the 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 was based on 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, 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 Project Team 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. This system assigns hazard ratings of low through extreme based on the scoring system shown in Table 2-2 and detailed in Appendix B.

Table 2-2. Hazard Rating Point System Used in the Nevada Community Wildfire Risk/Hazard Assessment Project
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 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 description of each of these factors and their importance in developing the overall score for the community is provided below. Individual community score sheets presenting the point values assigned to each element in the hazard assessment are provided at the end of each community assessment.

Community Design

Aspects of community design account for 26 percent of the total hazard 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 interface condition classes are used to categorize the wildland-urban interface: Classic Interface, Intermix, Occluded, and Rural. Definitions for each condition class are included 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.
  • 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. Fires have been known to start from arcing power lines or exploding transformers during windstorms or during periods of high electricity demand. 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 back-up 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 building 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 fire-resistant materials, there are steps that can be taken to address specific elements that strongly 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 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.
  • Architectural Features: Unenclosed or unscreened balconies, decks, porches, eaves, or attic vents 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 a wildland-urban interface area with these features implies a greater hazard to the community.

Defensible Space

Defensible space accounts for sixteen percent of the assessment score. Density and type of fuel around a home determines the potential fire exposure and potential for damage to the home. A greater volume of trees, shrubs, dry weeds, 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 losing the home. Defensible space is one of the factors that homeowners can most 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, Number, 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 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 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 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 behavior of a fire 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 can burn downslope; however, it usually burns downhill at a slower rate and with shorter flame lengths than in upslope burns. East facing slopes in the Great Basin routinely experience strong down slope winds in the afternoon 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 thick, continuous, vegetative fuels carry a higher hazard rating than communities situated in areas of irrigated, sparse, or non-continuous fuels. Dry weather conditions, particularly successive years of drought in combination with steep slopes or high winds, can create situations in which the worst-case fire severity scenario can occur.

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 types were mapped statewide and classified into four wildfire hazard categories (low, moderate, high, and extreme) based on the 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 fuel hazards.

The RCI Project Teams visited high and extreme hazard communities and verified the BLM fuel 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 fuel hazard layer of the project database. Photo points were established in high and extreme fuel hazard areas to monitor future changes in fuel hazard conditions. Fuel hazard mapping was completed for the Douglas County communities of Bodie Flats, China Springs, Genoa, Holbrook Junction, North Foothill Road Corridor, Sheridan Acres, Spring Valley/ Double Springs, and Topaz Ranch Estates.

2.3.4 Fire Behavior Worst-Case Scenario

The Fire Specialists on the RCI Project Team described a worst-case scenario for each community based on an 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 described in this document are 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 local area Fire Management Officers to obtain information on wildfire training, emergency response time, personnel, 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 dataset when possible. A list of fire agency personnel contacted for information used in the assessments is included in Appendix C.

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 were formulated based upon professional experience, quantitative risk assessment, and information developed in conjunction with the Living With Fire publications, National Fire Plan, and FIREWISE resources (National Fire Plan website; FIREWISE website; and Nevada Cooperative Extension publications).