Safely & effectively reducing fire fuels in the wildland/ urban interface

BY BRIAN BALLOU
All photos courtesy Oregon Department of Forestry

Reducing potentially flammable vegetation around homes and other structures in wildland/urban interface (WUI) areas gives both firefighters and homes a fighting chance against destructive wildfires. In many cases, you can reduce fuels without great cost, and the result is both effective and attractive.

It’s important to note that having defensible space around a home does not guarantee the home’s survival. Defensible space gives a home an edge against wildfire, but a structure’s survival often depends on whether firefighters and firefighting equipment take part in defending it.

Even walls of brick can't always keep a home from burning in a forest fire. Intense heat may have broken the windows, allowing fire into the home, or a blizzard of firebrands may have ignited this home's wood deck. Regardless, this home's defensible space was insufficient, and access for fire apparatus was poor — a half-mile long driveway bordered by dense strands of trees and thick brush. This home was one of five that burned in the 1,500-acre Deer Creek Fire.

Fuel Break Characteristics
How big should you make a fuel break? It depends on the risk. Every structure in a WUI area should have at least a 30' fuel break around it. Structures on steep slopes should have larger fuel breaks, about 50–100 feet, particularly on the downslope side. In areas where high-intensity fires are likely to occur or suppression support may be delayed or unavailable, you might need a 100–200' fuel break. And if a home has a long driveway with poor access for apparatus, a 200–500’ fuel break isn’t unreasonable; in these situations, the fuel break becomes a safety zone for trapped residents.

Fuel break composition is every bit as important as its size. Ground fuels must not allow fire to run unimpeded from the outer edge of the fuel break toward the structure, or vice versa. A few other important ideas to keep in mind when creating a fuel break include:

· Reduce ground-level fuels. A green lawn is an excellent barrier between a home and an advancing fire. Tall, dry, native grass is another matter. Trim native grass to four inches or lower. Rake and remove needle and leaf accumulations, or create fuel break paths to interrupt the transfer of ground-level fire. In many areas, it isn’t desirable to remove all the needles and leaves if doing so creates large patches of bare soil—which, in turn, become seedbeds for invasive or toxic plants that may create worse problems.

Grass fires don't often generate enough heat to ignite structures, but they quickly travel to heavier fuels that do. Forest fuels, firewood, lumber piles, and volatile landscaping plants can easily catch fire from burning grass, underscoring the need to keep tall, dry, native grass mowed inside a home's defensible space zone.

· Remove highly flammable landscaping vegetation, such as juniper, Scot’s broom and gorse. Aspen, rhododendron, kinnikinnick and other fire-resistant plants make better choices. There’s no such thing as fireproof vegetation, but fire-resistant plants, particularly if they’re kept green, healthy and arranged in scattered beds, greatly inhibit a fire’s ability to transfer. Discourage placement of landscaping beds directly adjacent to a structure’s siding, particularly beneath windows. Instead, favor dispersed planting beds and screens of fire-resistant plants that can help cover large exposures, such as the area beneath a deck.

· Thin trees and brush as necessary. This includes removing  ladder fuels, but bear in mind that healthy, fire-resistant species of trees, such as aspen, birch, crabapple, Oregon white oak, vine maple, red alder and mature Douglas fir, may help a home survive a wildfire by shielding the structure from radiant heat and firebrands. In all cases, remove dead trees and brush, and dead limbs on live trees and shrubs. When selecting trees to thin, look for suppressed trees, those of lowest vigor and those that have little live crown, signs of disease or insect infestation. Removing excess understory trees that are suppressed and damaged reduces ladder fuels and allows the remaining overstory trees to flourish and provide structures with a screen from radiant heat and airborne debris. Thinning brush also discourages horizontal plant-to-plant transfer of fire, as well as laddering; however, don’t remove so much brush or so many trees that you destabilize a slope. Even fire-vulnerable plants, such as western juniper and manzanita, can be less of a risk if you significantly reduce ground-level fuels and ladder fuels. Finally, work with local arborists, urban foresters or extension service agents on proper pruning practices and site-suitable replacement species and trees suitable for growing beneath power lines.

· Make the home’s driveway accessible. Clear away brush and overhanging branches to a minimum width of 12 feet and a height of 13 1⁄2 feet to ensure fire apparatus can make it up the driveway. Creating fuel breaks along both sides of the driveway is also a good idea, because doing so gives firefighters space in which to set up and go to work. Clear tight corners to improve visibility. On very long driveways, creating safety zones and vehicle turnouts is prudent. A safety zone should measure one acre in size and should be located on relatively flat land composed primarily of mowed grass that’s predominantly free of brush. Do not retain any dead vegetation in a safety zone. Thin or remove thickets of young trees, and remove older trees with ladder fuels. Turnouts should be at least 20 feet wide and 40 feet long. Mow any tall grasses located near the roadside, and remove ladder fuels and overhanging branches. In all cases, the foot of the driveway should include the house number, which should be easy to read, even at night.

Fire-resistant groundcover plants helped to slow the advance of the Deer Creek Fire as it approached this home. Firefighters were able to safely work on the green lawn that encircled the home, and the additional green space reduced the intensity of radiant heat.

Fuel-Reduction Strategies
The months from late fall to early spring are the perfect time to thin or prune trees and brush. (Fire season regulations often restrict the use of power-driven equipment, such as mowers, chainsaws and brush cutters, in the heart of summer.) There are many other things WUI residents can do to reduce the likelihood that a wildfire will start or spread on their property, such as:

· Remove debris from gutters. Needles, leaves and chaff build up in gutters during the winter and spring, then dry out during the summer months, becoming fuel that’s easily ignited by airborne firebrands. Gutter fires can ignite wood sheathing and stringers even beneath fire-resistant roofing materials. Covering gutters with metal mesh screening helps avert deep build-ups of fine fuel, but debris can still accumulate on top of the screens. The best medicine is to remove gutters entirely.

· Remove or isolate other flammables. Place firewood and lumber piles at least 20 feet from the structure, or fully enclose them in a shed or other building—covering them with a tarp won’t do it. It also doesn’t work to store flammables under decks or on exterior stairways. Radiant heat and airborne embers can easily ignite cans of gasoline, bottles of propane, wooden lawn furniture and bags of briquettes. Store flammables and explosives in an enclosed building, and mark them with a warning sign. Stacks of tires, abandoned appliances and vehicles also catch fire easily and should be removed from the fuel break area.

· Screen openings. Airborne embers and hot ash thrown aloft by a nearby wildland fire can start fires in a structure’s hidden places. Covering attic and soffit vents, foundation vents and the areas under decks and exterior stairways with a 1⁄4" (or smaller) metal mesh screen helps keep firebrands out.

· Establish a safe, debris-burning area. Although open burning is usually not allowed during summer months, it’s a good time to identify and prepare a permanent debris-burning site. Create burn piles where heat and flame won’t ignite adjacent vegetation. As a rule of thumb, make a horizontal clearing around the debris pile that measures three times the height of the pile (e.g., for a 2'-tall pile, the clearing must be at least 6 feet wide in all directions); this clearing should include a fireline dug or scraped down to the mineral soil with no dry grass, no tree limbs and no brush. Ensure the area above the pile is free of overhanging limbs and power lines. Burn barrels should be in good condition with screens over their tops; the screens should be constructed of 14-gauge wire with mesh no larger than 1⁄4 inch. Likewise, air vents must be screened. Make sure there’s at least 10 feet of open space around the barrel; clear the ground down to mineral soil, and don’t place the barrel beneath overhanging limbs or wires. When burning season begins, counsel property owners to keep a charged hose, a shovel and a phone close at hand whenever they conduct burns.

Effective & Attractive
Once a fuel-reduction project is completed, property owners usually enjoy the result, because they’ve improved their home’s visibility and airflow through their yard, and they’ve created distinct areas of sun and shade. Plants tend to thrive in such an environment, and structures often become less susceptible to moss, mold and mildew. In many cases, properties with cared-for fuel breaks have higher resale values than properties that are overgrown. Some typical value-adding characteristics of a fire-resistant landscape include:

· Many native, fire-resistant plants are also drought-resistant and require relatively little fertilizer.

· Moving landscaping beds away from structures and out from beneath roof eaves gives plants better access to sun and rain. It also relieves the structure from common problems caused by plants growing too close to a house, such as peeling paint caused by poor airflow and trapped moisture. Also, insects such as spiders and ants don’t have such easy access to the house.

· When selective thinning removes understory trees, overstory trees tend to flourish, making them less vulnerable to drought, insect and disease.

Conclusion
The key to making a functional, attractive, reduced-fuel zone around a house: Plan the project thoroughly. Don’t fire up the chainsaw and start whacking away indiscriminately. Identify the property’s wildfire-risk factors and develop workable options for mitigation.

Work with knowledgeable contractors on thinning and plant-replacement aspects of the project. Consult experts, such as urban foresters and extension agents, to develop a list of trees and shrubs that will thrive on the site and won’t interfere with permanent structures and utilities. In all cases, work closely with the property owner, listen to their concerns and arrive at workable compromises that meet both fuel-reduction and long-term livability needs.

Brian Ballou frequently teaches wildland/urban interface residents about ways to keep their houses from burning down. In his day job, he’s a wildland/urban interface specialist and a public information officer for the Oregon Department of Forestry.

Online Resources
Firewise
www.firewise.org: This site provides a one-stop source for fire-reduction
information.

Oregon State University Extension Service’s “Wildfire in Oregon” http://extension.oregonstate.edu/emergency/wildfire.php: This site offers
a variety of information, including an excellent guide to fire-resistant plants.

The International Code Council
www.iccsafe.org/safety/wildfire.html: This site features simple guidelines
for defensible space, tips for building in areas prone to wildfires and excellent
downloadable illustrations.

To obtain a copy of  The International Urban-Wildland Interface Code 2003, go to http://egov.oregon.gov/OOHS/SFM/docs/Comm_Ed/2003_WUI_Code.pdf:
This book is an essential resource for anyone developing standards, rules and ordinances for interface areas.