City of Boulder Community Wildfire Protection Plan

A WUI includes both interface and intermix communities. It's where human habitation and development meet or mix with wildland fuels.

• Interface areas include housing developments that meet or are in the vicinity of continuous vegetation.  

• Intermix areas are those areas where structures are scattered throughout a wildland area where the cover of continuous vegetation and fuels is often greater than cover by human habitation. 

In the WUI, fire can easily spread between buildings and vegetation, increasing the risk of wildfires and potential loss of life and property. Factors like fire suppression policies, land use changes, climate change, and insect infestations have intensified this risk. It's crucial to adjust fire management practices and policies and understand and manage fire risk in the WUI.

The map to the right is the 2024 WUI map of the City of Boulder Planning area. Use the slider tool to view the map with and without the WUI layer.  

This map does not contain discussion of building codes, which can be found in a separate, designated WUI map specific to this code.  View the map here.    

As seen in the building code map, areas identified by various colors show the level of fire-resistant construction materials required under the current code.  

What is Urban Conflagration? 

Urban conflagration is a large, uncontrollable fire that spreads quickly through urban areas, threatening buildings, infrastructure, and lives.  

Why is it a Concern? 

In Boulder, the risk of urban conflagration is particularly relevant due to the city's location within the WUI — areas where residential communities meet natural wildlands. Factors like drought, high winds, dense development, and climate change increase the likelihood and potential severity of these fires. 

Strategies for Mitigation and Preparedness:

• Education and Regulation: Public campaigns and fire safety regulations help reduce risk by promoting safer building practices and land use. 
• Community and Household Mitigation: Actions include managing vegetation around homes and modifying structures to make them less flammable. 
• Emergency Preparedness: Investments in early warning systems, better firefighting equipment, and training improve readiness and response capabilities. 
• Suppression and Resilience: Effective firefighting strategies and community resilience programs ensure quicker recovery and adaptation to future threats. 

Specific Actions for City of Boulder Residents: 

• Manage Vegetation: Reduce the amount of flammable vegetation near homes. 

• Space Out Trees: Increase spacing in the tree canopy around properties to decrease fire spread. 

• Build Responsibly: Use non-combustible materials for construction and ensure adequate space between buildings. 

Wildfires pose a higher risk to specific groups in Boulder, including individuals with disabilities, the unhoused, non-English speakers, those without access to a vehicle, and other individuals with functional and access needs. These groups are often situated in high fire risk areas and may use open flames for warmth and cooking, increasing their exposure to fire hazards. 

The City of Boulder CWPP uses the SVI data from the Center for Disease Control and Prevention (CDC) and Agency for Toxic Substances and Disease Registry (ATSDR), which is based on the U.S. Census Bureau’s American Community Survey. This index helps identify the areas and populations that are most at risk and require targeted fire mitigation and emergency preparedness efforts. 

Measuring social vulnerability is complex due to limitations in data availability, reliability, and the appropriateness of the geographical scale of the data. The SVI provides a framework but also has inherent challenges, including the accuracy of data in small or rural populations and the selection of indicators that may not have been empirically tested. 

Recognizing these vulnerabilities allows Boulder to tailor communication and emergency response strategies to effectively support these populations in the event of a wildfire, ensuring that preparedness and response efforts are inclusive and equitable. 

The vegetation zones in the City are mainly determined by elevation, slope, aspect, substrate, and climate. Because the City has a wide range of elevations and topography, the characteristics of vegetation communities vary. 

Vegetation model results are mapped as a 30 square meter grid on the landscape to create a gradient (raster) of probability for metrics such as burning, operational control, and risk to structures.

Much of the eastern portion of the planning area consists of mixed-grass prairies. While a significant portion of these grasslands are used for agriculture, native grasses still dominate the landscape. Agricultural practices such as grazing, and irrigation help mitigate wildfire risks.

To the west, the Rocky Mountain Front Range foothills host various forest types, including but not limited to ponderosa pine woodlands, dry mixed-conifer forests, and subalpine forests.

Each vegetation type's unique fire regime has implications for local fire management practices. In grasslands, managing the timing of agricultural activities and controlling invasive species are key to reducing fire risks. In forested areas, strategic fuel reduction and controlled burns can help maintain natural fire cycles and reduce the severity of wildfires. 

 The maps on the right show vegetation types (right) and their corresponding fuel models (left) in the planning region. Fuel models are a reflection of the vegetation type, which are used by fire behavior models to predict the type of fire behavior that can be expected if those fuels burn. These layers are at a 30m x 30m resolution, with each assigned a vegetation type, which is then converted to the appropriate fuel model.   

The fuels in the planning area shown on the left are classified using Scott and Burgan’s (2005) Standard Fire Behavior Fuel Model classification system, where each vegetation and litter type is broken down into 40 different models. The general fuel groups are classified as: 

• (NB) Non-burnable 
• (GR) Grass 
• (GS) Grass-Shrub 
• (SB) Slash-Blowdown 
• (SH) Shrub 
• (TL) Timber Litter 
• (TU) Timber-Understory 

Fire behavior fuel models results are mapped as a 30 square meter grid on the landscape to create a gradient (raster) of probability for metrics such as burning, operational control, and risk to structures. 

To toggle between the two maps, move the slider back and forth. Open the legend by clicking the bottom left icon on the map.

 Learn more about the fuel models here.  

Quantitative assessments of wildfire risk rely on three main factors: the likelihood of a fire happening, the expected intensity of the fire, and the location of resources and assets (e.g., homes, infrastructure, trails, etc.) in relation to vegetation that can fuel the fire.

This map shows the expected risk to a structure if it were to occur on the landscape in that location.

Click on the buttons below to change the map to the right to Wildfire Risk to Assets. This map allows the user to understand wildfire risk to existing Highly Valued Resources and Assets (HVRAs). The resources and assets include people and property, infrastructure, water, and vegetation.

Use the buttons below to toggle between the "risk to potential structures" and "risk to assets" maps.

Technical details regarding the development of the "Expected Risk to Potential Structures" and "Wildfire Risk to Assets" maps are available for reference in Chapter 3 and Appendix D of the CWPP.

Goal 1 of the Cohesive Strategy and the Western Regional Action Plan is: Resilient Landscapes.

The strategies below are put forward to provide guidance and suggestions on actions to address wildland fire risk. Tailoring fire management activities to individual sites is essential. The protection of community values and sensitive ecosystems are key considerations for wildfire fuel mitigative actions. It is at the discretion of City of Boulder representatives and land managers to determine when or if a recommendation will be implemented.  

 See the CWPP recommendations focused on Resilient Landscapes here. 

The City of Boulder, along with other local land management agencies and other cooperators, implements prescribed burns as part of a comprehensive fire management strategy. The strategic areas for these burns are selected to optimize wildfire resilience, improve public outdoor spaces, and support healthy ecosystems, following detailed consultation with experts and landowners. Conducted by trained firefighters and certified wildland staff, these burns are carefully planned and executed in collaboration with agencies such as Boulder County and the USFS. 

The City of Boulder also conducts agricultural prescribed fires to help maintain open space agricultural properties, including ditches that provide water for open space farming and ranching operations. Prescribed fire in agricultural ditches removes vegetation from important irrigation infrastructure and helps control plant growth and invasive weed species. 

Areas of concern are places with high fuel loading, expansive WUI, high wildfire risk, and valuable assets such as energy infrastructure.

The map to the right shows the specific areas of concern delineated during the CWPP update process. They require priority attention for wildfire risk mitigation. The delineation of these areas is based on Core Team expertise and a variety of mapping products including risk to assets, expected risk to potential structures, the WUI delineation, wildfire hazards, fuel models, probability of control, Potential Operational Delineations (PODs), and aerial imagery.  

In the City of Boulder's planning area, the dominant fuel types identified include various grasslands and timber areas, each characterized by distinct fuel loads and vegetation structures. Recommended treatments below can be applied across the planning area depending on site-specific conditions. 

 View Dominant Fuel Types and Recommended Treatments    

In the maps to the right, the user can explore existing past and planned fuel treatments (left) in addition to the fuel treatments recommended in this CWPP (right). These recommended fuel treatment projects were created collaboratively by the Core Team in multiple meetings through the analysis past fuels treatments, PODs and AOCs, risk and hazard data, and public input among other factors. Click on individual treatment recommendation polygons to learn more. As a reminder, the CWPP make recommendations but does not mandate any actions.

Goal 2 of the Cohesive Strategy/Western Regional Action Plan is: Fire-Adapted Communities.

Actions on the landscape play a role in reducing wildfire hazard, but public education and community engagement are equally vital. Lack of knowledge and failure to take positive actions, such as creating defensible space, contribute to increased risk in the WUI. Collaboration among residents is crucial in communities with neighboring structures to reduce wildfire risk collectively.  

The Recommendation Table for Supporting Fire-Adapted Communities lists recommendations for reducing structural ignitability and identifies activities that emphasize the importance of tailored public education and engagement programs. 

 See the CWPP recommendations focused on Fire-Adapted Communities here. 

Defensible space refers to how defensible or fire-resistant the area within the home ignition zone is. Removing all flammable vegetation in the immediate zone is the best course of action for reducing structural ignitability.  

Defensible Space Treatments Include: 

• Thinning trees.  
• Limbing or pruning trees and shrubs from the ground up.  
• Implementing hardscaping such as rock mulch, patio, and watered lawns.  
• Removing flammable hazards such as firewood, outbuildings, and hazard trees.   

The goal of home hardening is to decrease the ignitability of homes. Home hardening upgrades can be simple and often work best when paired with adequate defensible space in the home ignition zones.

To better understand the importance of defensible space,  please watch this YouTube video.  

Intermediate Ignition Zone  

The area 5 to 30 feet from a structure should be managed to slow wildfires. Keep trees spaced and trimmed to prevent fire from climbing into the canopy. Regularly clear dead vegetation and mow tall grasses.  

Extended Ignition Zone   

This zone extends from 30 to 100 feet from a structure. Reduce fuel by thinning trees and removing dead debris. Prune lower branches and maintain clean underbrush to lower fire intensity. 

Roof   

Use fire-resistant roofing materials like Class A asphalt shingles or metal. Keep roofs clear of debris to prevent ember ignition.  

Fencing  

Wooden and other combustible fencing materials pose significant risks during wildfires. These materials can easily ignite from flying embers, and act as a continuous line of fuel, dramatically increasing the fire's reach and speed across residential areas. Non-combustible materials for fences, such as metal or stone, can help create a defensible space by preventing the spread of fire to your home. 

Ornamental Plants   

Choose fire-resistant plants with high moisture content. Space plants to prevent continuous vegetation paths. Prune shrubs and trees to prevent ground fires from climbing. 

 For more ideas, view the homeowner/renter actions table here.