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  • What is the Wildland-Urban Interface (WUI)?

    The wildland-urban interface (WUI) is the area where urban and suburban development meets undeveloped areas containing natural vegetation. It can be a beautiful, quiet place to live, but with the benefits of being near nature come risks. One of the most pressing is wildfire, but others include risky interactions with wildlife such as bears and mountain lions, as well as physical phenomena such as floods and landslides. Within the greater WUI, areas are classified as to their relative fire hazard severity zones. These are areas in mountains, foothills, and canyons where adjacency to vegetated areas, difficulty of access, and weather patterns pose greater risk of wildfire.

    CAL FIRE and the fire response agency in each local jurisdiction have determined where these areas are, and require the management of vegetative fuels near buildings. To find out if your property is in a fire hazard severity zone, contact your local fire agency.

    The WUI can also be subdivided into three categories: intermix, interface, and occluded / interior.

    • An intermix WUI is where development, such as structures, is interspersed or scattered throughout wildland vegetation. An intermix WUI is often found in rural, exurban, or large-lot suburban developments.
    • An interface WUI is where development, such as structures, is grouped near areas with wildland fuels. There is a clear line of demarcation between development and vegetation, which may appear as an abrupt edge between a highly urbanized or suburban neighborhood and a wildland area—for example, when development borders public lands or when urban growth boundaries are in place.
    • An occluded or interior WUI is an urban environment where structures abut an island of wildland fuels, such as a community park, open space, greenbelt, or other natural area.

    Planning the Wildland-Urban Interface (American Planning Association, 2019)
    Wildland Fire Safety Starts in the Home (UC ANR, 2019)

  • What is a sustainable defensible space?

    The United Nations defines sustainable development as “meeting the needs of the present without compromising the ability of future generations to meet their own needs.” In the wildland-urban interface areas of Southern California, living sustainably means protecting yourself, your family, and your property from risk, while also protecting natural habitat.

    Native plants are essential ecosystem components and provide habitat for native birds, butterflies and other wildlife. California is known as a global hotspot for its diversity of unique plants and animals. To preserve this natural heritage, it’s important to live responsibly in the wildland-urban interface. For more on our State’s threatened biodiversity, visit

    Good fire preparation in your landscape can help protect wildlands from damage, but sustainable and fire-wise gardeners also conserve water, limit the use of potentially harmful chemicals such as fertilizers and pesticides, and avoid invasive plant species. Sustainable fire-wise landscaping should be easy to care for. Many native and California-friendly plants grow slowly and maintain high levels of moisture in their leaves and stems with little irrigation. By choosing these plants, you can protect the health of neighboring habitat and create a beautiful low maintenance garden.

    Wildland Fire Safety Starts in the Home (UC ANR, 2019)

  • What is a defensible space?

    Defensible space is the area around a structure free of flammable plants and objects. It creates a zone in which firefighters can operate safely in order to help protect a home during a wildfire. This space is wide enough to prevent direct flame impingement and reduce the amount of radiant heat reaching the structure. The defensible space for each structure varies, depending on the type of vegetation and topography. Planned defensible space that reduces radiant and convective heat allows fire suppression personnel to work in a safer environment.

    A Road Map to Fire Safety (SMMFSA, 2010)

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