Defensible Space (fire control)
This from an article on Wikipedia.com
In the context of fire control, defensible space is the area around a structure that has been landscaped to reduce fire danger. "Defensible space" is also used in the context of wildfires, especially in the wildland/urban interface. This space reduces the risk that fire will spread to the structure, and also provides firefighters a relatively safe area in which to work while protecting the structure. In areas prone to wildfires, firefighters will often not attempt to protect structures that do not have adequate defensible space, both for safety reasons and because such efforts are unlikely to be successful.
Most agencies recommend that the defensible space around a structure extend for at least 100 feet (30 meters) in all directions. This area need not be devoid of vegetation, but plants should be selected, trimmed, spaced and irrigated in such a way to minimize the fuel available to the fire and hamper the spread of the fire.
The term Defensible Space referes to the 100' surrounding your property or structures. The first 30' around a structure, is where vegetation is to be kept to a minimum, also called the "Defensible Space Zone". A concept often used in this area is the "low, lean and green" concept, describing a basic and simple way of achieving and remembering how your property should be maintained in the first 30'. The distance of 30'-100' in the Defensible Space zone is usually refered to as the "Reduced Fuel Zone". In this area of the defensible space, fuels/vegetation are to be separated vertically and horizontally depending on the vegetation type. Spacing guidelines can be met by thinning, pruining, limbing up trees from nearby vegetation, or removal of selected vegetation types and the separation of tree canopies. The Defensible Space zone can be required to be more than 100' if the given topography of the parcel would make the initial 100' not as effective.
One concept in Defensible Space is "Reducing the Fuel". This is where you selectively thin plants and prune them to reduce the fuel volume of the remaining plants. The idea is to break up the more continuous and dense vegetation, instead of having an uninterrupted layer of vegetation.
Another concept is "Ladder Fuels". Like rungs on a ladder, vegetation can be present at varying heights. Grounds fuels, like grasses can transmit fire to shrubs and then into the trees limbs. When trees catch fire they start to produce and cast embers that can result in spot fires making it more difficult to control a wildland fire. Three times the height of the lower fuels is the typical separation for ladder fules. I.E. If you had Shrub "X" that was two feet high, just under Tree "X", you would want to have a spacing of 6 feet between the lower limbs of Tree "X" and Shrub "X". That can be obtained in a couple of different ways. Remember fire burns uphill faster than on flat land or a down slope. So spacing may need to be greater if on a slope.
If you live in a wildland/urban interface it is important to maintain fire-safe landscaping. Pick plants that are naturally fire resistive, then MAINTAIN them! If you choose to not maintain fire resistive plants they can dry up or die and become part of the problem again. Use a good irrigation system and keep all vegetation free of dead debris. This will help maintain the fire resistance of the plants and keep your landscaping looking nice.
Keep access roads, including driveways, clear of vegetation. Maintaining access allows large emergency equipment to reach your home. Clear combustible vegetation at least 10 feet from roads and driveways. If the fire department can't get to your home, they can't save your home. Also be aware of verticle clearance. Any trees or vegetation that hangs over roadways needs to be cut to a height of at least 13 feet 6 inches. But make sure that is the typical height of responding apparatus to your area, it could be greater. Also make sure that you have your streets and homes clearly marked. If the fire department can't find your home, they can't save your home.
