3.1 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.

Teams 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) during the assessment process. 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.

3.2 Base Map Data Collection

The assessment teams were provided with maps containing geospatial data reviewed and compiled by project resource information system specialists. Data sources for the maps were the Nevada Fire Safe Council, the Nevada Department of Transportation, the Natural Resource Conservation Service, the Forest Service, and the BLM. Data includes:

• Land ownership
• Fire history
• Vegetation communities
• Wildfire fuel hazard
• Topography
• Current aerial photographs
• Soil surveys
• Roads

This data was then field verified during the data collection phase of the Community Risk/Hazard assessments. Geographic information system specialists then provided the system management that would guarantee the effective analysis of the statewide geospatial data and the production of the maps in this report.

3.2.1 Wildfire History

Wildfire history information was obtained from BLM and USFS GIS databases that locate 21 years of wildfire perimeters. Fires were mapped by agency personnel using GPS and screen digitizing and source maps with a minimum detail level of 1:250,000. This data set was compiled at the Nevada BLM state office from information provided by all of the field offices at the end of each fire season. The data set is intended to be a central source of historical GIS fire data for the support of fire management efforts and land use planning.

As a result of interviews with local fire experts, the project teams identified fire perimeters not present in the BLM dataset. These perimeters were drawn on the field maps then screen digitized into the project’s wildfire perimeter dataset.

In addition to the fire perimeter information, point data for all fire ignitions within Nevada from 1980 to 2003 was incorporated into the dataset. This information was obtained through a query to the National Interagency Fire Center (NIFC) database housed in Boise, Idaho, as reported by participating agencies. This data does not consider fire size, and in many cases, the location of the fire is only accurate to within the section. In such cases, the fire is located in the center of the section (Figure 2-2).

The fire history data and ignition patterns were used 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 risk exists due to a buildup of fuels or expansion of urban development into the interface area.

3.3 Community Risk/Hazard Assessment

The wildland/urban interface is the place where homes and wildland meet. This project focuses on identifying hazards and risks in the wildland/urban interface areas countywide, assessing each community individually. Site-specific information for each community was collected during field visits conducted between March 1 and March 4, 2004. The predominant conditions recorded during these site visits were used as the basis for the Community Risk/Hazard Assessment ratings.

3.3.1 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 community risk values (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. Copies of the rating sheets used by the project teams and copies of the Community Risk/Hazard Assessment summary sheets are provided at the end of each community section. Photographs of each community are provided in Appendix C.

Community Design

Community design accounts for 26% of the total score of the risk 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: Rural, Intermixed, Occluded, and Classic are defined in the glossary (Appendix A).
• Access. Design aspects of roadways influence to the hazard rating assigned to a community. A road gradient of greater than 5% 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 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 are a potential ignition source. Fires have been known to start from arcing power lines during windy conditions. In the event of a fire, a burning power pole could contribute to a short, causing power failures downline. A power failure in a community without backup energy generation may leave residents without water for protecting their homes and leave firefighters without pumps for the town’s fire suppression water system. Energized power lines may fall and create an additional hazard for citizens and fire fighters. In some areas these downed power lines could block road access. Properly maintained rights-of-ways (ROWs) underneath power lines greatly reduce the risk of fire ignitions along power line corridors during fire events.

Construction Materials

Construction materials account for 31% of the total score of the risk 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 risks associated with hazardous 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.
• 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 risk 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% 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.
• 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 or just certain structures.

Physical Conditions

Physical conditions account for 27% 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 types and density, the physical conditions in and around a community cannot be altered to make the community more fire safe. Understanding these physical conditions, fire behavior specialists can predict fire growth patterns and help fire suppression personnel respond appropriately to a fire threatening a community. 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. The 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 conditions. 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 most at risk due to topography in the event of a wildfire.
• Fuel Type and Density. Vegetation type and density around a community affect the potential fire behavior. Areas with thick, continuous, vegetative fuels are at a higher risk 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.

3.3.2 Hazard Mapping

Wildfire hazard mapping was completed statewide by the BLM for areas surrounding communities listed as at-risk for wildfires. During the assessment it became clear that, while all communities have some risk to wildfire, in many communities that risk is very low. This may be due to agricultural land surrounding the community or simply a very sparse, desert vegetation type. Community selections for hazard assessments and hazard mapping revisions were based on the BLM hazard data layer, site visits, and professional judgment.

The assessment began by reviewing the wildfire risk potential data compiled by the Nevada and Utah BLM. Their hazard delineation process is based on vegetation type. The Nevada Gap Analysis Program vegetation dataset was used to define vegetation type. This dataset, derived from satellite data, maps land cover across the entire state in 30-meter cells, and classifies each cell into one of 65 vegetation types. A team of fire specialists from the BLM 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 sage 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 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.

3.3.3 Fire Behavior Worst-Case Scenario

The worst-case scenarios described in this document are based on the project wildfire specialists’ estimation, given observed fuel loading conditions, of what could happen during a set of weather conditions resulting in severe fire behavior occurring in conjunction with 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.

3.4 Interviews with Fire Personnel

The Project Team interviewed local fire department personnel to obtain information on wildfire training, emergency response time, personnel and equipment availability, evacuation plans, and 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 B for a list of persons contacted.

3.5 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 to the risk of fires and how to reduce that risk, and coordination among fire suppression agencies to optimize efforts and resources. The 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 National Fire Plan and FIREWISE resources (National Fire Plan website, FIREWISE website and Nevada Cooperative Extension publications).