What Is the WUI?

What exactly constitutes the WUI has been (and continues to be) a point of debate. The National Wildfire Coordinating Group (NWCG) defines the WUI as “the line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.” The National Fire Protection Association (NFPA) defines the WUI as the “locations in which the [authority having jurisdiction] determines that topographical features, vegetation fuel types, local weather conditions, and prevailing winds result in the potential for ignition of the structures within the area from flames and firebrands of a wildland fire.” Recent research suggests that as much as 10%—or more than 175 million acres—of the United States is classified as WUI land by these definitions.

For the purposes of grant applications, specific definitions have been developed to help departments distinguish between population distributions. One example is the difference between rural, suburban and urban response areas when applying for Assistance to Firefighter Grants. For practical purposes, however, the distinguishing factors are certainly not that clear or well defined; some piece of the WUI exists in all regions, states, cities, towns and counties. Even the emerging concept of “open space islands” has created areas within urban centers that have the same properties and response concerns as traditionally identified WUI areas.