Defensible Space Is Not Enough

Creating defensible space is essential to improve your home’s chance of surviving a wildfire. It’s the buffer you create between a building on your property and the grass, trees, shrubs, or any wildland area that surround it. This space is needed to slow or stop the spread of wildfire and it protects your home from catching fire – either from direct flame contact or radiant heat. Defensible space is also important for the protection of the firefighters defending your home. – Source: http://www.readyforwildfire.org/defensible_space.


Destroyed homes and the Angora Fire, 2006, Lake Tahoe, CA.

When their name was still the ‘California Department of Forestry’, CAL FIRE’s Defensible Space program was intended to prevent house fires from becoming forest fires. With more taxpayers building homes in fire-prone areas, a shift has occurred; instead of ‘protecting forests from the people‘, we now aim to ‘protect people from the forest‘. This sense of separation – where the ‘wildland’ that drew people out of the cities has become their greatest enemy – is perhaps our biggest obstacle in learning to live with wildfire.

Massive wildfire-caused structure losses happen every few years, yet our messages remain the same: Cut your brush, prune your trees, move your woodpile, replace your shake roof…
It is not working. We need to redefine how we think about protecting communities. As long as Defensible Space is perceived as a ‘contingency’, rather than as a ‘strategic’ action, we will fail to take advantage of the opportunities that having defensible, fire-permeable communities present to us, namely, the ability to reintroduce fire into wildlands near our communities, or even let naturally-ignited fires do the heavy lifting of managing our wildland vegetation.

Understanding Fire’s Place on the Land

Each place has its own relationship with wildfire, and for many places, fire suppression is effective in controlling most ignitions. The ‘really bad fire’ that escapes control may only come to town once or twice in a lifetime. The rapid spread of the recent Valley Fire may have surprised most, but history shows us that large fires aren’t uncommon in Lake County, or in most of California.

The Valley Fire started near the town of Cobb, South of Clear Lake, on September 12th, 2015, around 1 pm. By 6:30 pm, the fire had burned over 10,000 acres (15 square miles), and was still growing rapidly. The final fire size was over 75,000 acres, and at least 1,900 structures were burned (sources: CAL FIRE, Wikipedia)

The map below – from the Lake County Website – shows ‘before and after’ satellite images of the areas burned by the Wragg, Rocky, Jerusalem, and Valley Fires, in 2015. The Valley Fire is the one on the left. (Note, the map is easier to use if you click ‘Hide Intro’).

The 2015 wildfires in Lake County were fuel and wind driven. While the severity of the current drought certainly contributed to the size of the fires, like most of interior California, there is drought EVERY summer, the vegetation is mainly highly flammable brush and grasslands, and Lake County has a history of regular, large wildfires.

This map shows previous large fires that have burned within Lake County. Source: Lake County CWPP.

Many of the homes destroyed by the Valley Fire lacked defensible space clearance. The map below was created by Lake County News using damage inspection data provided to them by Lake County. It shows many of the destroyed structures in the communities of Cobb Mountain, Hidden Valley Lake, Middletown and the surrounding areas.

Click on the Satellite layer on the map below, and zoom in to take a look at which parcels were destroyed (red dot) or survived (no dot) the Valley Fire. Note that many of the destroyed homes had trees right up against the structure. Many of the lost homes are in such dense forest that they are not even visible from above.

Another striking detail in the damage map, above, is the fact that many of the destroyed homes were in the middle of towns, or had their legally-required clearances, with no trees or shrubs near the home.

Under extreme, windy conditions, many homes that survive the passage of the main flaming front of the fire are lost later due to small fires started by flying embers. One way to increase the odds that your house will survive an emberstorm is to tidy up junk piles, old tarps, leaves in gutters or roof valleys, and other flammable kindling-type clutter on or adjacent to your house.

The (scary) video below shows fire behavior on the 2013 Clover Fire, in typical interior California live oak/gray pine foothill fuels. Like the Valley Fire, this wind-driven fire also destroyed many of the structures in its path. Note that the structure in this video has good clearance, including a bulldozer line between it and the fire. Even so, this house burned.

One consequence of increased development in the wildlands is that when a fire starts to threaten homes, nearly all of the incoming firefighting resources end up parked in peoples’ driveways protecting homes, waiting for the fire to come to them, instead of going out to where it is burning and putting it out. This is the difference between ‘structure protection’ and ‘perimeter control’, and it results in larger fires. When an IC orders ’40 engines, any type’, they are really saying ‘I need firetrucks in here right now to save houses, I don’t care if they are heavy urban engines that can’t leave a paved road, because they are not coming here to put the fire out’. (Obviously, there is nothing wrong with saving peoples’ homes – defensible space makes it easier for firefighters to do more with less).

Living in wrong-relationship with wildfire puts you, your belongings, and our emergency responders in harm’s way. Anything that wildland-dwellers can do to have a property that ‘doesn’t need saving’ frees up resources and people to do entirely different things with their time; like restoring fire to our forests, or staying home to play with their kids.

Improving Wildfire Safety for Your Home.

The best thing that we can do to improve the safety for individual homes is to address the conditions in the forests and wildlands that surround them. The single best reason to fireproof your home is so we can get to a point where the public is comfortable with wildfire as a natural occurance, and we no longer need to extinguish every new ignition. Defensible Space is a step in the right direction. Also, it’s the law.

California Public Resource Code 4291 requires that homeowners in wildfire-prone areas maintain defensible space around their dwelling. CAL FIRE conducts defensible space inspections in many areas, and may require landowners to clear brush and hazardous fuels if their property is not in compliance with PRC 4291.

To see the factors that CAL FIRE evaluates during their inspections, you can download the CAL FIRE Defensible Space Inspection Form.

A few basic tips to increase home wildfire safety:
Roofing – Shake roofs are a leading cause of home loss in wildfires. Research show that homes with non-combustible roofs and clearance of at least 30-60 feet have a 95% chance of survival in a wildfire.

Vent Openings – Screening of vent openings with steel screens will prevent embers (during the ember blizzard that comes with a wildfire) from entering into attics and crawl spaces. Smaller screen sizes (1/8th inch) are more effective at keeping embers out, but can also plug with dust, decreasing their ability to actually do their job of ‘venting’ the attic.

Siding – Untreated wood siding significantly adds to the radiant heat and flame impingement exposure risk from wildfire.

Eaves – Eaves often add to the home’s exposure from wildfire by trapping direct flames and embers. Building construction practices should be modified to reduce the susceptibility of eaves to direct fire and firebrand ignition.

Decks – If treated and maintained properly, and with adequate defensible space from vegetation, most solid wood decking material is fire resistant enough to withstand the short term heat load. Research shows that treated natural wood products must be well maintained to prevent cracking or rotting and maintain their fire resistance. Many new materials (synthetics) ignite more easily than wood and have a rapid structural collapse when subjected to high heat loads. On slopes, the area beneath decks catch flying embers. It is a good practice to screen these areas to keep embers from blowing in during a fire.

Detached Structures – Flammable Structures (e.g. storage, wood & tool sheds, and fencing) without separation from homes, place those homes at risk of loss as they can act as ‘wicks’, carrying fire to the house.

Woodpiles – Woodpiles without adequate separation expose structures (homes and other buildings) to sustained heat and fire. During the fire season, roughly May through October, wood piles should be located away from residences.

Propane Tanks – Propane tanks should be clear of flammable vegetation for at least 10 feet.

Junk – Ratty tarps, piles of lumber, old boats, and anything else that can catch flying embers and catch on fire should be kept away from your house.

Research has found that prep work done in the zone within 10′ of the house is the most important in determining whether or not a house will burn. There should be at least a couple of feet of fireproof ground cover – dirt or gravel – right up against the home.

Working at the Community Level

In many places with small lots, you can do everything right and still lose your home if your neighbor hasn’t done their part. While maintaining the shrubbery and trees that give you privacy is always a high priority, there are many ways that you can increase the survivability of your home, and do your part in maintaining community fire safety without creating a moonscape around your home.

We work with communities to help them map out their wildfire hazards, and develop on-the-ground projects to improve community wildfire safety. We recently completed two different wildfire hazard reduction plans for forested communities in Plumas County. The slideshow below captures some of our recommendations from those projects, providing vegetation management prescriptions to decrease the risk of extreme fire behavior in Sierra/Cascade forests while maintaining plant diversity and wildlife-friendly conditions.
Click here to view a larger slideshow.

Contact us if you’d like to learn about more resources for community wildfire safety and prescribed fire.

September 27th, 2015

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