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August 13, 2013 > Planning for urban wildfire

Planning for urban wildfire

By Thor Poulsen

Fire in the hills can occur where urban-interface areas pose threats to citizens and homes. An urban-interface fire creates complex challenges for firefighters. Residents in or near an urban/wildland area, should design and maintain their homes and landscaping with wildfire-safety in mind. Simple steps to make a home fire-safe, inside and out, not only reduces the threat to the property but helps protect families.

Everyone in these areas should understand some basics and be prepared. Construction materials, landscaping plants and design, surrounding wildland fuels, home location on a slope or flat area affect exposure to, and threat from, wildfire.

Fuel includes anything that will burn - trees, shrubs, grass, homes, fences, decks, sheds and more. Unchecked, an urban wildfire makes no distinction between wildland and urban fuels - between grass, trees or a home. Preventative measures, however, can alter a fire's behavior and reduce risk.

Low-lying fuels, such as grass and shrubs, often carry a fire more quickly than larger fuels but usually at lower intensities and with shorter flame-lengths. However, if they form a continuous path to a deck or home, the property can burn as easily as in larger fuels.

Just as firefighters create firebreaks in the wildland, it is important for property owners to create space between plants and establish breaks in landscaping to alter a fire's path to the home.

Ladder fuels are grasses, brush and shrubs that carry fire from low-lying, surface vegetation into tall trees. Confine a fire near the surface and reduce its intensity by trimming or removing ladder fuels near trees and keep low-hanging branches trimmed to a minimum of six feet above the ground.

Crown fuels are tall trees which, once alight, are difficult to manage and often pose the greatest threats because of high temperatures, high burn-intensities, long flame lengths, the probability of spreading embers widely, and more. Stands of trees should be thinned to create space between them, with branches trimmed and out of contact with the ground. Trees next to and touching a building are best removed.

Critically, weather affects a fire's intensity and rate of spread. High temperatures, low humidity and wind can make a wildfire in grass or brush as dangerous and threatening as a crown fire and exacerbate the intensity and spread of crown fires. A long, dry spell or drought conditions only intensify a wildfire's behavior and threat.

When considering one's home, understand that wind can carry embers and firebrands up to more than a mile from the main fire. Embers landing on a roof or in gutters containing leaves, or other flammable debris, or getting trapped beneath or on decks, are responsible for the loss of many homes each year.

A property's surrounding terrain must be considered. Fires tend to burn uphill more quickly and intensely than downhill or across flat areas. This effect is worse, if the upslope includes a narrow drainage, called a chimney, which can funnel and intensify the wind and flames.

Buildings at or near the top of a slope are at a greater risk and require proper landscape management over a greater distance downhill than on flat ground to reduce risk by an equivalent amount.

What can homeowners do?
First, reduce the property's exposure and flammability; this entails one or more steps ranging from installing a fire-resistant roof to removing debris from beneath decks, keeping roofs and gutters free of leaves and other flammable material and storing firewood away from the house.

Second, reduce and manage fuels surrounding the home to increase fire-resistance. This ranges from keeping the landscaping low and clean near the building to raking away leaves and other debris and creating enough space between trees and plants to slow an approaching fire.

Think and act in zones
When preparing a property to withstand a wildfire, think in terms of zones and consider a 200-feet radius around the home. In some cases, this may require working with neighbors or other landowners.

Zone 1: Home Ignition Zone
The most critical area is the "home ignition zone" which includes the building and landscaping within a 30-feet radius. Wind-blown embers and firebrands can ignite a home while leaving the surrounding vegetation untouched or only charred. Better protection of this zone includes removing leaves or other wooden debris from gutters and roofs; clearing away vegetation and debris from under decks and any touching the foundation; ensuring eaves and attic vents have a small, quarter-inch screen; keeping firewood away from the building; and keeping vegetation in this area trimmed short, well-irrigated, free of dead material and spaced apart to prevent a continuous path of fuel to the structure.

Zone 2: Defensible Space Zone
This is the second-most critical zone and includes the area between 30 feet and 100 feet around the building. Remove dead and dying grass, shrubs and trees; thin vegetation and ladder fuels and keep them free of dead material; and replace hazardous vegetation with less flammable, irrigated landscaping, including lawn or low-growing ground cover and flowering plants.

Zone 3: Wildland Fuel Reduction Zone
In this zone, 100 feet and beyond, remove dense undergrowth and thin densely-crowded smaller trees. Experts recommend a 10-feet gap between trees and shrubs. The lowest branches on mature trees should be at least six feet above the ground, out of reach of fire.

There are many measures to enhance the survivability of one's home when wildfire occurs but each step, no matter how small, can make a big difference. Multiple steps can vastly reduce risk and subsequent loss.

When fire strikes
Waiting until smoke is in the air, before taking precautionary measures, is too late. When a fire occurs nearby, be prepared to evacuate. Park the car facing out of the garage or in the direction of departure. Gather important and irreplaceable photos, documents, heirlooms and pets and put them in the car. Take flammable deck or patio furniture indoors and move all flammable furniture away from windows. Close all windows, doors, vents, blinds and non-flammable window coverings. If possible, turn off all gas and propane utilities. Leave on a porch or outside light. Listen to local TV or radio for evacuation news. Local authorities may also drive through the neighborhood with public announcements. Leave immediately when asked to do so.

Every year, across the Nation, some homes survive, while many others perish in major urban wildfires. Properties belonging to owners who prepared for the eventuality of fire, which is an inescapable force of nature in fire-prone areas, are the ones that usually survive.

For more information on Disaster Preparedness-related materials visit and click on the red "Disaster Preparedness" button or contact the Hayward Fire Department Emergency Services Office at (510) 583-4948.

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