How To Be Wiser About Wildfires
Voice of San Diego
August 30, 2010
This is the season to get the message out that although wildfires can be extremely destructive, they are not like tsunamis or tornadoes: with the right information, people have a chance to make wise choices, and can reduce their risk of losing a home by making the wisest changes they can afford to make. Who wouldn't want to reduce home losses in a wildfire? I think that it could happen in our region, when enough people understand a few basic facts: how homes burn and how to reduce the risk of that happening.
Basic fact number one: Most homes ignite in a wildfire from embers igniting the home itself, or a structure close to the home. A few ignite from superheated air, especially from other burning homes, and even fewer ignite from the actual wildfire flames.
Basic fact number two: there is no such thing as a "fire-safe" plant, but there are "fire-wise" people.
Home Ignition Risks from Wildfires:
Embers: 80 percent of home ignitions in a wildfire are caused by embers landing on the house and igniting the house, due to the home's flawed design and construction. New homes now must be built to standards that will prevent ember ignition. Older homes that have not been retrofitted against ember attack are at high risk.
Live embers can land from a fire five miles away. Fire-wise professionals tell us the only way to protect older homes is to retrofit them to resist ember attack. Some fixes are cheap: installing attic and foundation vent screens and adding screens to tool-shed windows, and weather-stripping garage, sunroom, and shed doors. But wood shake roofing is the greatest hazard of all, and a new roof, or replacing small dimension handrails or exterior stairways with heavy timber or metal, or replacing windows and doors, are expensive.
Heat: some homes are destroyed in a wildfire after igniting from heat radiated from an adjacent burning building. For example, a tool-shed ignites because it had unscreened windows and embers got in. The tool-shed radiates heat up to 2000 degrees then ignites the house. In suburban areas, where homes may be as close as 10 to 20 feet apart, 2000 degrees radiating from a burning home will ignite the adjacent homes. Each home that has been made low-risk will also protect its neighbors.
Flame: Flames moving from the wild-lands across the homesite cause a small percentage of home ignitions, compared to homes ignited by embers. Assume the area for 100-foot around the home is fire-wise. If so, the wildfire flame is too far away to ignite the house. A fire-wise homesite, out to 100 feet from the home, will have non-combustible latticework, decks, sheds, fabric structures and furniture, gravel mulch and fences within five feet of the house, and plants that are lean, clean and green.
If homeowners spent $1,000 a year on the lowest-cost retrofit items — vent screens, weather-stripping, a bit of fencing, etc., — they would reduce their risk a lot in a few years. However, replacing a wood roof, siding or decking, or putting in fire-resistant windows are big home improvements, and some people simply may not be able to do them. One home that is still a high risk can threaten a whole neighborhood. Santa Barbara, after suffering huge home losses from wildfires, now requires these improvements be made as point-of-sale upgrades. Is this something San Diegans should consider? Other models exist: communities could accept donations for non-profit funds to help neighbors who can't afford to do the most important work. This kind of mutual assistance would be very fire-wise.
Homesite Risk Reduction:
How to keep the homesite from igniting? Assure that all the man-made materials for shade structures or furniture near the house are noncombustible, or keep them in storage when not in use, and decide how best to keep the plants noncombustible. No magic plant exists that will protect a home, though some require a lot less work to keep from igniting. Any plant, even the low-maintenance ones, still needs two things in order to not ignite: cleaning and water.
Every year before fire season, cut down dead weeds, remove leaf litter over two inches deep, and clean off roofs. Then keep going: green hedges, beds of ferns and succulents, and some plants like junipers, rosemary, and cypresses build up a dead layer under the green foliage. Clean out all that dead stuff before July, and during fire season remove new buildup is removed. Some plants can be cut very short in the summer and regenerate in the cool wet season. If a plant is too much work to maintain, learn if anything else can be planted that is less work. Make decisions carefully.
A plant list with water needs and cleaning requirements would help people be more fire-wise. Plants need water to be hydrated and resist ignition. Many species need water three times a week, and without it, will dry and die. Dead and dry plants ignite. Others require much less water, and need it less frequently, to be hydrated. If water is limited in your homesite or your budget, less thirsty plants will help you have a low-risk homesite with the water they need, some only three times a month.
For a homeowner with a tight budget for maintenance, plants that require less water and less cleaning, e.g., small trees versus big trees, will have a lower-cost, low-risk landscape. But some people like bigger trees and are able to invest more to maintain a landscape of more high-upkeep plants, and still have a low risk homesite. Both are fire-wise, as long as the homesite is clean and plants are hydrated through fire season.
A Better Future:
These pre-defended homes and communities would be likely to survive in a wildfire. A pre-defended home with a wildfire approaching will need someone to shut windows and, if they have it, to spray aon a fire-retardant foam for extra insurance.
When the smoke clears, we all could return to our lives in our communities, and the charred wildlands would start on its natural post-burn healing cycle. What a different future that would be, than the one we presently anticipate when wildfires threaten. And yes, it is possible, if we choose wisely and make it happen.
-- KAY STEWART, San Diego
Kay Stewart is a California registered landscape architect. Many local experts can help homeowners learn more. Wildfire Zone lists many of them,