In 1990 the Colorado State Forest Service conducted a study that concluded that over 1.5 million acres of urban/suburban development in the state bordered on highly flammable wild lands. Since that time this situation, known as "urban/wild land interface," has increased dramatically. Simply put, this means that thousands of Colorado homes are at risk.
Insurance companies have become concerned about this very real danger, and are issuing warnings to policy holders. Their insurance could be canceled, and new clients could be refused coverage if they do not correct fire hazards in and around their homes in high risk Front Range zones.
Our Colorado ecosystems evolved with wildfires. For at least 12,000 years wildfire has been a common, rejuvenating ingredient in these natural environments. Not so today, for ever since European-Americans began arriving here in the mid 19th century, we have brought about countless changes that have altered the natural fire regime. Overgrazing by cattle, fire suppression and the outlawing of control burns, mining, building railroads, and development have all contributed to our current situation.
Of most significance to those whose homes and businesses border wild lands is a tremendous increase in flammable fuels in our forests: deadwood, crowded trees with dead branches, leaf and needle litter, dry grasses and weeds. In one western forest similar to ours the US Forest Service estimated the accumulated fuel to equal 280 gallons of gasoline per acre. The usually moderate wildfires of old are escalating into catastrophic firestorms as a result.
Far too many people who have located in areas of great risk are blissfully unaware of the danger and have done little if anything to protect themselves and their property. According to a recent article in the Rocky Mt. News, only about 10% of homeowners in the Front Range areas of greatest risk (Red Zone) have acted on the concerns of insurance companies to eliminate fire hazards.
Consider that in 1996, six million acres were devastated by wildfires with as many as 22,000 firefighters on the lines. Between 1993 and 1998, 50 firefighters lost their lives battling wildfires. And the danger is increasing, not diminishing.
The great Yellowstone fires of 1988 are a prime example with 1.4 million acres consumed — more than in the Park’s entire 116 year history, which collectively totaled a mere 146,000 acres burned prior to 1988. Ten thousand firefighters battled the Yellowstone fire to no avail.
How dangerous is it really? In 1991 a wildfire in Northern California’s Oakland foothills destroyed 3,354 homes, 456 apartment buildings, and killed 25 people. Two years later a wildfire that began in the Laguna Beach foothills laid waste to 441 homes. What is illuminating about this fire is that one house survived unscathed while those packed around it on all sides were turned to ash. This house had a fireproof roof, stucco walls, extra insulation and a fire resistant landscape. A good fire resistant landscape can increase a home’s survival by as much as 90% in a wildfire.
No, this isn’t California, but before we write off the comparison let’s recall the 2000 acre Black Tiger Gulch Fire above Boulder in 1989, where 44 homes and buildings were destroyed in just six hours. The few homes which survived this inferno had defensible landscapes. The following year 11 homes and 6000 acres were consumed in the Old Stage Fire just north of Boulder. In 1996, just two fires, the Buffalo Creek and the Dipping Vat Fires burned 28,331 acres in Colorado. The owners of 900 homes and buildings a mere five miles north of the Buffalo Creek Fire which destroyed seven homes, were fortunate indeed.
All of these were forest fires, but nearly every year Front Range homes are lost to prairie fires as well. Deborah Frazier recently reported that the Colorado Front Range is second only to southern California in wildfire severity in the US (5/9/99 Rocky Mt. News).
Home and business owners in the urban/wildland interface should realize that there are many things they can do to protect their properties and their lives. And it is their responsibility. Firefighters will rarely if ever attempt to protect homes they consider indefensible; after all, their lives are at stake and fighting a losing battle to save an unprotected home takes up precious time better devoted to fighting the fire more strategically.
While space doesn’t permit an in-depth discussion of all the ways to protect our families, homes and properties against wildfire, here is a blueprint which, if followed, will make all the difference.
Fire resistant landscapes, or firescapes as they are sometimes called, are essential protection for fire safety. The firescape must be developed within a specific sized area called "Defensible Space." On a flatland site this extends out from buildings to 30 feet or more in all directions (space permitting). On a 30% slope Defensible Space is 60 feet or more downhill from buildings and 45 feet or more out in other directions. A slope of 55% requires 120 feet or more downhill and 60 feet or more in the other directions. These areas have been determined based on wildfires' tendency to increase in rate of velocity as the degree of slope becomes greater. A wildfire burning across flatlands will double its speed when it contacts a 30% upslope. When the upslope reaches 55% the rate of advancing fire quadruples. Wildfires are capable of advancing 300 to 2000 feet per minute.
Within the Defensible Space, existing trees, especially "pyrophites" like pines, firs, junipers and other conifers rich in highly flammable resins and oils, must be thinned to widely spaced canopies. Those in close proximity to the house should be removed. A dehydrated pyrophite can literally explode from the advancing heat before the flames even reach it. Shrubs, particularly those against the house or under the canopy of a tree, should either be removed (grubbed out, i.e. dug out by the root) or pruned back regularly and all deadwood routinely removed as they can send up flames four times their height. On trees that remain after thinning, all branches six to ten feet above ground level should be cut out, but no more than one third the tree’s height on smaller trees. Grasses, weeds and perennial herbs that have died back should be kept cut back. Thick piles of leaves should be picked up and composted. Dry dead materials become fuel, and the primary function of Defensible Space is to keep fuel to a minimum.
A firescape utilizes fireproof materials like boulders, gravel, crushed rock, flagstone and brick, often applied liberally. Landscape plants should be low growing species that generate a small volume of fuel. Plants with succulent or thick, leathery leaves are the most resistant to burning. A few thoughtfully sited shade trees are fine, but use only deciduous broadleaf trees which contain far less flammable oils and resins and are far more resistant to fire than pyrophites. Broadleaf trees should be no closer to houses than 20 feet and their branches should be pruned out where they grow over the roof. Also, keep branches at least 15 feet away from chimneys and equip your chimney with a spark arrester and clean it often.
Lawns or fire resistant patios are best situated on the down slope side of the house. Rock or cinderblock firewalls can be constructed for added protection. Living firewalls can also work on the right kind of sites, providing there is ample available water and plants that have a high water storage capability are used.
Water is your biggest ally against fire. Even fire resistant and drought tolerant plants should be deeply irrigated during dry periods for they will burn readily if they dry out. If a fire is heading your way, a good soaking of the ground and even the house itself can afford some needed protection. Just remember that you will also need water to fight the fire if it reaches you. Well water will seldom be enough so storage tanks, cisterns or storage ponds are recommended.
Even within the urban/wildland interface some places are more dangerous to build on than others. Homes and buildings constructed in narrow canyons, in saddles, and at ridge line are at greatest risk. Canyons and saddles channel fire and it races ahead at a faster rate, Ridge tops are dangerous because by the time fire hits the crest it is traveling at maximum speed.
As for the buildings themselves, the roof is the most vulnerable to fire. All roofs should have fireproof coverings approved by the underwriter’s laboratory. Routinely clean leaves and other flammable debris off the roof and out of the rain gutter.
Have a plan for yourself and your family to escape a fire, and practice it until it is clear in everyone’s mind.
Joshua Smith, a landscape designer and plantsman with many years of professional experience, lives in Niwot, Colorado. His specialty is functional ornamentals, such as edible, medicinal, and fire resistant plants. He is also a practitioner of permaculture, ecological forestry and wildfire mitigation.
Originally appeared in the August, 2000 issue of The Colorado Gardener
