Wildfire Fuel Management

Cover photo - prescribed fire at Monan's Rill (Courtesy of Julia Murphy)

In the past five years alone, fire has consumed about 25% of the county’s landscape, destroying 7,500 structures and killing dozens of residents. To reduce the risk and severity of these catastrophic wildfires, our community needs to take coordinated action.

Fire is not new to our Mediterranean landscape. For thousands of years, fire was a regular and important process in California that helped create and maintain healthy forests and ecosystems. Pre-colonization, Indigenous land management used controlled burns as a means of shaping the structure and composition of vegetation across our land. The result is that Sonoma County is within a fire adapted ecosystem; fires are an integral part of our environment. Today’s forests are less healthy and more prone to severe wildfires due to decades of fire suppression, changing land use patterns, and climate change.

Fuel management, both immediately around homes and across landscapes, is one of the most important and effective tools we have in wildfire mitigation and prevention. To assist Sonoma County residents in managing their landscapes and properties, the University of California Cooperative Extension (UCCE) and Pepperwood have developed the    Wildfire Fuel Mapper.    The Wildfire Fuel Mapper is a set of online tools and resources to help residents and land managers with properties greater than 3 acres assess their fuels and take action to reduce fire hazard. 

This story map is part of the Wildfire Fuel Mapper, and is designed to:

• Provide background on wildfire and fuels in the region
• Introduce fuel management strategies around the home and on the landscape
• Provide access to property and watershed maps
• Outline a how-to guide for taking action

Following a series of catastrophic fires, many North Bay communities are taking action to protect their homes by actively managing vegetation and reducing fuels around their home and property.

What can you do? Pre-fire activities increase the chance that people and homes will survive. These activities include treating fuels near homes and roads, hardening structures to reduce ignition risks, and managing vegetation on your landscape.

In order to start planning a fuel management project, it’s important to understand the basics of wildfire, fuels and fuel treatments. This section provides an overview of the following basic fuel treatment concepts: the Wildland Urban Interface, wildland fire types, ladder fuels, defensible space, and home hardening.

The Wildland Urban Interface (WUI) is defined as a zone of transition between human communities and wildland areas. These communities are often at high risk for wildfire threat because of the proximity to forests and dense vegetation. In Sonoma county, over 50% of residents live in the WUI. The WUI is determined and mapped by considering fuels, burn probability, and the location of human assets such as structures on the landscape. The maroon areas in the map below shows the WUI as mapped by CAL FIRE. For detailed methods on how CAL FIRE created this dataset, click  here .

Structure density is an important component of the WUI. The interactive map below shows 2018 structure density (red is high structure density, yellow moderate, green low, no color is no density). The areas shaded in red have the highest housing density. The purple circles show the number of structures in a given area. Zooming in allows you to see the locations of individual structures.

There are three types of wildfires - ground fires, surface fires, and crown fires.

1. Ground Fires smolder beneath the surface layer of litter, burning duff and other organic material in the soil. 
2. Surface Fires burn leaf litter and other downed fuels like branches and logs, as well as some surface-level plants like bushes or small trees; larger woody plants and trees are largely left alive. These types of fires are considered lower severity and seen as beneficial to the health of the forest.
3. Crown Fires. When fires become more severe and burn up the tree canopy, they're known as crown fires. Crown fires are difficult to control and often kill large trees, destroy structures, and lead to the loss of life.

Ladder fuels connect surface fuels to crown fuels. Small trees, tall shrubs, and branches can act as ladder fuels by carrying a surface fire upward into the tree canopy. Having a lot of built-up ladder fuels can lead to larger, more destructive crown fires.

Fuel within 100 feet of structures is the primary cause of home ignition from wildland fires. Managing fuels around homes and structures is one of the key ways we can reduce fire risk and protect our communities from wildfire.

Home Hardening focuses on lowering the risk of home ignition by making changes to housing materials, design, and maintenance. These include replacing siding, decking, or roofing with more fire-safe material, covering vent openings with metal mesh, and implementing other types of retrofits. Learn more about  hardening your home  and  low or no cost home updates .

Defensible space is the 0-100 foot area around a structure that is maintained to remove fuels, reduce the risk of ignition, and “defend” the home from wildfire threat. Landowners are required to create defensible space within 100 feet of structures (or to the property line, whichever comes first). This area is critical to save the lives of residents and firefighters, to reduce fire spread from house fires into surrounding wildlands, and to lower the risk of home loss. Guidelines for creating defensible space are provided below.

• "Zone 0-Non-combustible": 0 - 5 ft. from building walls. Remove all combustible materials from this critical five feet. 
• "Zone 1-Lean, Clean and Green": 5 - 30 ft. radius from structure walls. Maintain this zone clear of highly flammable vegetation, including removing all dead and dying vegetation, creating separation between trees and shrubs, removing ladder fuels, and keeping grasses low and irrigated. 
• “Zone 2”: 30 - 100 ft. from structures. Remove dead and dying vegetation and ladder fuels, keep trees and brush separated so that fire can't spread towards buildings. 
• “Zone 3”: 100+ ft. from structures. This area includes vegetation and fuels beyond the home, and fuel management in this zone is further discussed in the next section.

Download your property and watershed maps and check the “CAL FIRE Responsibility Areas for Firefighting” section on page 1 to learn more about what zone your property falls into. View complete defensible space requirements for Sonoma County at the following links:  State Responsibility Areas (SRA)  and  Local Responsibility Areas (LRA). 

Defensible space and home hardening are critical to saving lives and protecting individual properties. At the landscape level, managing vegetation and fuels further away from our homes (Zone 3) is also essential for reducing fire risk.

Fuel treatment is designed to alter the types, amounts and arrangement of fuels, which can lead to fewer, smaller, and less damaging fires. Fuel management requires careful planning, working with treatment specialists, and constant upkeep.

A primary focus for vegetation management should be the removal of ladder fuels, such as dead and dying vegetation and plant debris, low-growing brushy plants, and low tree limbs that spread fire quickly.

Fuel treatment is not a one-size-fits-all: the exact treatment type depends on characteristics of your property and vegetation. Working with an expert is necessary to create a treatment plan that is right for your property and meets local regulations.  There are many ways of treating and reducing fuels, ranging from mechanical removal of vegetation with a chain saw to prescribed burning. The main main types of fuel treatments are described here:

Mechanical Treatment

Mechanical treatment involves cutting grasses, shrubs and/or trees through the use of hand tools and machinery such as chain saws, chippers, and sometimes larger machines. Mechanical treatment is the most common type of fuel treatment employed in Sonoma County.

Mechanical treatments are used to remove ladder fuels, thin dense stands, and create fuel breaks. Often, the brush and slash created from mechanical treatments is chipped, masticated, or burned. Tools for mechanical treatment include chainsaws, chippers, and sometimes larger machines.

Prescribed Grazing

Prescribed grazing involves using animals to reduce grasses, shrubs or the understory of forests and is an effective maintenance method to control fuels and prevent regrowth. Prescribed grazing is especially effective at reducing grassland fuels during the fire season.

Prescribed Burning

Prescribed burning is the use of controlled fire to manage vegetation and reduce fuel loads. Controlled burns reduce the volume of fuels through combustion. These burns are conducted under specific regulations, when conditions permit, and require proper personnel, equipment and permits. Prescribed burning in forests is almost always preceded by mechanical treatments.

The following figure provides a simplified diagram of the history of two drivers of fire - fuels and ignition hazard - in our region. The figure shows three distinct eras:

This era was marked by Indigenous land stewardship, which relied heavily on fire as a tool for managing vegetation for game, acorn and seed production, and materials for tools and baskets. 

Margo Robbins, a member of the Yurok tribe in Northern California and executive director of the Cultural Fire Management Council explains:

“From those beginning times until a little over a 100 years ago, fire was the primary tool we used to keep the land healthy, to make good habitat for animals and people… We burned from the coastline to the high mountains, at different times of the year and at different intensities.”

Controlled fire in the region decreased as European settlers did not recognize the ecological value of fire on our landscapes, preventing burning that was practiced by Indigenous people. By the late 19th century, controlled fire was effectively removed from the landscape of Sonoma County.

This era was marked by intensive harvesting and grazing. Timber companies harvested most of Sonoma's old growth redwood and Douglas-fir and laborers harvested hardwood woodlands to produce firewood and charcoal for a growing Bay Area population. Farmers cleared land for pasture and crops and extensive grazing kept already cleared land from converting back to shrubland and forest. The intensive and largely unregulated activities in this era had many adverse effects, but did prevent the build-up of fuels.

The modern era is marked by a confluence of trends in climate, land management, and demography that has resulted in increased fuels and risk of ignition on the landscape. Coupled with warming temperatures and longer fire seasons, these factors have resulted in an increase in fire in recent years - a trend predicted to continue. The following discussion addresses each of these factors:

1. Increased fuel - The present era has brought a reduction in both grazing and the harvesting of timber and firewood, coupled with an increase in fire suppression. In California, the lack of low intensity fire and management has resulted in a shift in the vegetation across our landscape. Not only is there a greater volume of vegetative fuel, there is also an increase of fire prone species, such as Douglas fir and California bay trees, that are crowding out our more fire resilient oak woodlands.
2. Increased risk of ignition - Since 1935, Sonoma County's population has grown from 65,000 to 500,000. Today, roads, houses, and power lines reach across and into areas of the landscape where they did not exist before. With this 800% increase in population comes an large increase in ignition hazard.
3. Warming temperatures and increased aridity - A slowly changing climate, increasing temperatures and longer fire seasons have resulted in more flammable fuels than in the past.

The following comparisons of historic and modern imagery illustrate how changes in management and population have altered forests in the region and led to increased fuel and ignition hazard on the landscape. Sonoma County's earliest air photography is from 1942, so we'll use that imagery to illustrate conditions at the beginning of the modern period.

 The following sections give an overview of approaches to fuel management and the tools and resources needed to implement your own fuel management project. 

 Fuel management should carried out in ways that mirror the natural disturbance cycles of an ecosystem, mimicking the effect of natural fire regimes. The benefits conferred by well-planned treatments increase forest health and fire resilience.

This section summarizes 5 simplified steps to develop and implement a fuel reduction project.  A more detailed version of these steps with specific guidelines and resources  is available here  in the Wildfire Fuel Mapper User Manual. If you are a property owner, download a custom map report for your property  here  as you navigate the process outlined below.

Step 1: Set General Vegetation Management Goals

Consult vegetation management specialists and experts: Before implementing your project, make sure to consult with local specialists , who can help identify your property’s hazardous fuels, based on your Wildfire Fuel Mapper map report, and advise on next steps in your project. It is critical to work with an expert in designing your project to ensure you are following regulatory requirements and applying appropriate pre-treatments.

Set general vegetation management goals: Setting clear and defined vegetation management goals serve as the foundation for a successful project. Examples of goals can include reduced fuels, increased biodiversity, increased forage, improved habitat and carbon sequestration. Land owners and managers should brainstorm goals with a specialist or expert to determine appropriate vegetation management goals to meet the needs of the property and regulatory constraints.

Step 2: Gather Information

Understand requirements and regulations: Prior to any significant vegetation management projects, it is important to review federal, state, and local regulations or requirements. The location and status of your property will determine which agencies have the primary duty to help you prevent and suppress fires, and which regulations you must adhere to. Find your property’s designation in your Wildfire Fuel Mapper map report and explore the map below to view different regulation zones.

Conduct Environmental Mapping: Planning an approach for reducing fuels requires maps and information about your landscape. Maps can help you better understand fuels, forest type, fuels, slope, roads, buildings, and streams and lakes. These maps can be shared with experts as you create your treatment plan. The Wildfire Fuel Mapper report includes many helpful maps. Users may wish to acquire additional maps that clarify their property’s assets. Scroll down to the end of this story map, or click the 'Property and Watershed Maps' heading to access your map report, available for properties in Sonoma County greater than 3 acres or of entire watersheds.

Step 3: Make a Plan

Determine a treatment plan: Using the Wildfire Fuel Mapper maps and reports, landowners can meet on site with experts such as foresters, UC Cooperative Extension advisors, or RCD staff to assess their landscape and specify areas on the maps as targets for different types of fuel treatments. The exact locations, size, and type of fuel treatments will depend on the vegetation type and arrangement of fuels on the landscape, location of human assets, topography, weather patterns, and other factors. The Wildfire Fuel Mapper maps provide information useful for planning an appropriate fuel treatment.

Find Funding Assistance: There are various funding opportunities and cost share programs available through local, state and federal agencies to help you implement your fuel treatment plan. Additionally, agencies such as the Natural Resource Conservation Service (NRCS) assist landowners with free technical assistance and cost share programs to help offset the costs of management practice implementation. Additional information on these funding opportunities can be found on our website under  “Data and Resources” .

Step 4: Implement your treatment plan:

Once you are ready to move forward with your project, use the information you have gathered to begin implementing your chosen fuel treatment strategies. Effective and sustainable management of vegetation often requires integrating several treatment options.

Step 5: Sustainable Upkeep

To maintain a fire resilient landscape, fuel management is a continuous effort.  Over time, vegetation grows back and fuel treatments need to be repeated.  After a fuel reduction project is conducted, it is important to monitor the conditions of the treatment area.  As early as 5-10 years post-treatment, new growth of vegetation may require a second treatment. Following treatments will require much less work in areas that have already been treated. 

As fires continue across Sonoma County, fuel management will be critical to protecting our communities now and in the future. The Wildfire Fuel Mapper provides you with the tools and resources needed to understand and begin managing your fuels.