2.1 Project Team

The RCI Project Team, composed of experts in the fields of fire behavior and suppression, forest and rangeland ecology, and geographic information systems (GIS), collaborated to complete a Community Risk/Hazard Assessment for each of the identified communities in Clark County. The RCI Project Team included Fire Specialists with extensive wildland fire experience in Nevada and Southern California and Resource Specialists experienced in the Mojave Desert environment.

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 hazardous fuels and landscape features, community design, 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

Geographic Information System (GIS) 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 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 are summarized in Table 2-1.

Table 2-1. Primary Datasets and Sources Utilized in the Clark 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	Field Interviews
Roads	“TIGER” Census data (2000)
Current Aerial Photographs	US Geological Survey Digital Orthophoto Quadrangles (1994, 1996, or 1998)
Fuel Hazard Classification	BLM Nevada and Utah 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, Utah

2.2.1 Wildfire History

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 covering the past 21 years. This database was compiled by agency personnel using global positioning system (GPS) and screen digitizing from source maps with a minimum detail of 1:250,000. The dataset is updated by the Bureau of Land Management Nevada State Office at the end of each fire season from information provided by each Nevada Bureau of Land Management Field Office. The dataset is the central source of historical GIS fire data used for fire management and land use planning on federal lands.

Fire Specialists on the RCI Project Team identified additional fire perimeters that were not present in the Bureau of Land Management and US Forest Service datasets during interviews with local fire experts. Fires that occur on private lands are generally recorded on paper maps and have not been consistently included in the federal agency GIS datasets. Additional fire locations identified during the interviews with local fire personnel were recorded on the field maps where possible and added to 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 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, summarized in Table 3-2, provides the ignition point locations for the maps in this report. In cases where the ignition point data is only accurate to within the section, the point coordinate is located on maps in the section center.

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 agencies were also 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 risks and hazards in the wildland-urban interface areas countywide by assessing each community individually. Site specific information for each community in Clark County was collected during field visits conducted between March 17 and April 2, 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

Fire Specialists on the RCI Project Team assigned an ignition risk rating of low, moderate, or high to each community assessed. This rating is based on four sources of information: interpretation of the historic 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 Fire Specialists on the RCI Project Team, 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.

Table 2-2. Hazard Rating Point System Used in the
Nevada Community Wildfire Risk/Hazard Assessment Project

Hazard Category	Score (points)
Low Hazard	Less than 41
Moderate Hazard	41-60
High Hazard	61-75
Extreme Hazard	76 or higher

To arrive at a score for the community, five primary factors that affect potential fire hazard were assessed: community design, construction material, 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. Photographs of representative fuel types for each community are provided in Appendix C.

Community Design

Aspects of community design account for 26 percent of the total hazard 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 interface condition are included in the glossary in Appendix A.
• Access. Design aspects of roadways influence the hazard rating assigned to a community. Roads less than twenty feet in width often impede two-way movement of vehicles and fire suppression equipment. A road gradient of greater than five percent can increase response times for vehicles carrying water. 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 signs and adequate driveway widths also reduce the overall community score.
• 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 citizens 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 throughout the interface areas accounts 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 strongly affect structure ignitability in the interface area. Factors considered in the 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 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; thereby, presenting a much lower ignition risk from firebrands or the proximity of advancing flames when defensible space conditions are adequate.
• Architectural Features. Unenclosed or unscreened balconies, decks, porches, eaves, or attic vents on homes can create drafty areas where sparks and embers can be trapped, smolder, ignite, and rapidly spread fire to the house. A high number of houses within a wildland-urban interface with these features implies a greater hazard to the community.

Defensible Space

Defensible space accounts for sixteen percent of the assessment score. The density and type of fuel around a home determines the potential fire exposure levels and the potential for damage to the home. A greater volume of trees and 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 losing the home. 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 capabilities 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 firefighters 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 firefighters to respond to a reported wildland fire or 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. 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 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, topographic location, fuel type, and fuels density. With the exception of changes to the fuels composition, 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 influence the behavior of a fire is essential to planning effective preparedness activities, such as fuels 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 with 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. West and south facing aspects are subject to more intense solar exposure, which preheats vegetation and lowers the moisture content of fuels, increasing the potential for hazardous fire behavior. Canyons, ravines, and saddles are topographical 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.
• 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.

2.3.3 Fuel Hazard Mapping

Fuel hazard maps were initially generated by the Bureau of Land Management Nevada and Utah State Offices using wildfire hazard delineations derived from vegetation satellite data at thirty-meter resolution (Nevada GAP Analysis Program). A total of 65 vegetation types were mapped statewide and reclassified 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 an extreme fuel hazard, while sparse Mohave shrublands were rated as low fuel hazards.

The RCI Project Team visited high and extreme fuel hazard communities and verified the Bureau of Land Management fuel hazard information by comparing the hazard ratings on the existing fuel hazard maps to observed vegetation, slope, and aspect conditions. Where necessary, changes to the ratings were recorded on maps and used to update the wildfire hazard potential layer of the project database. Hazard mapping was updated for seven communities in Clark County. 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 Clark County communities. In this report, hazard maps are provided only for those communities where high and extreme fuel types were noted.

2.3.4 Worst-Case Wildfire Scenario

The RCI Project Team Wildfire Specialists described the worst-case scenarios included in this evaluation based on their analyses of the severe fire behavior that could occur given a set of weather conditions, observed fuel load conditions, slope, aspect and minimal fire suppression resources. The drought conditions and dry vegetation in combination with steep slopes or high winds can create situations in which the worst-case scenario can occur. The worst-case scenario does not describe the most likely outcome of a wildfire event in the interface, but it does illustrate 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 fuels reduction recommendations.

2.4 Interviews With Fire Personnel

The RCI Project Team interviewed local fire department personnel and local Fire Management Officers to obtain information on wildfire training, emergency response time, personnel and equipment capability and 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. A list of fire agency personnel contacted for information used in the Clark County assessment 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 use of 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 community hazard score, and information from published references such as “Living With Fire” and FIREWISE resources (National Fire Plan website; FIREWISE website; and Nevada Cooperative Extension).