More than 740,000 residences in the western U.S., with estimated value of more than $136 billion, are at “high” or “very high” risk of sustaining damage from a wildfire, with 168,000 of the “very high” risk residences valued at more than $32 billion, according to a new report by CoreLogic.
CoreLogic focused on the Wildland Urban Interface (WUI), the area where urban development and wildland meet. Fires are most often attributed to wildland areas, so the best way to recognize high-risk residential structures is to locate the WUI.
Approximately 17 million new homes were built in the U.S. between 1990 and 2008. Ten million of those were constructed in the WUI. About 40 percent of the 115 million individual dwellings in the U.S. are located within the WUI. The past two decades have seen a significant increase in homes lost to wildfire, which corresponds with an increase in residential development in the WUI.
Wildfires have caused billions of dollars of property damage in the last two decades alone. Human activities cause more fires each year than lightning, be it a cigarette or sparks from power lines. Some research centered on climate change speculates that changing weather patterns may impact the risk of wildfires, but this has not been determined for certain. U.S. forest fire policy in the 20th century might also be contributing to risk rather than mitigating it. While wildfire statistics fluctuate, it is believed that they do so in a slight cyclical pattern, which has become more pronounced over the last decade. States where the risk is traditionally highest—Texas, Oklahoma, New Mexico, Arizona and Colorado—have seen record-breaking wildfire damage in 2011 and 2012.
CoreLogic has several methods of evaluating wildfire risk. The initial step is to divide risk in categories based on fairly stable variables such as terrain, fuel and vegetation. Terrain aspects, such as the direction a slope faces and how steep it is, contribute to how fast a fire can move. Fuel and vegetation density indicate how intense a wildfire might become.
CoreLogic uses these variables to determine Low, Moderate, High and Very High risk categories. Urban and agricultural areas are defined separately because of an absence of natural fuels and the resulting lower risk profile. This risk model does not factor in short term changes in climate and weather. It is not designed to identify ignition points or predict a current fire’s progression.
(Graph source: The Blue Ribbon Panel Report on Wildland Urban Interface Fire, 2008.)
After CoreLogic has created categories, it then assigns each property a wildfire risk score from 1 to 100. The score comes from considering risk inside of an individual property boundary and the property’s distance from nearby high-wildfire-risk areas. A score of 50 or below indicates very little to no wildfire risk. Scores between 81 and 100 indicate properties with the highest susceptibility to wildfire.
The risk score process places more than 900,000 properties in the 81 to 100 range, a total estimated value of $161 billion. The reason for the discrepancy is that the scoring method considers fire’s ability to grow when wind-blown embers are carried over longer distances. CoreLogic assures that despite the differences in numbers, both methods accurately define potential wildfire risk.