WUI - Wildland Urban Interface
The Wildland–Urban Interface (WUI) is a zone of transition between undeveloped wildlands and human development, specifically the area where houses meet or intermingle with undeveloped wild vegetation. Communities in the WUI are generally at a greater risk of exposure to wildfires. In Marin, WUI is a political boundary and designation adopted by local and county jurisdictions based on input from fire agencies and GIS analysis to determine the communities and locations that meet this definition. In Marin, all structures in the WUI and/or State Responsibility Areas are required by law to maintain defensible space.
Wildland Urban Interface, or "WUI" is NOT a designation of potential wildfire severity - it's a somewhat loosely defined description of an area where urban development meets undeveloped lands at risk of wildfires. Some definitions of WUI exclude areas where development density falls below a certain threshold, so a single house, far from others may not be considered to be in the "WUI" even though it's in the middle of a wild area and potentially at risk of exposure to wildfires. Conversely, areas with dense development may not be considered WUI because of the high housing density, even though they may be close to wildlands and at risk of conflagration during extreme wildfire events.
In Marin, WUI "maps" were first developed by County government in the late 1990s, based on the federal definition at the time. These boundaries have changed somewhat over time, and the maps may - or may not - have been updated to capture new development. There are also political considerations - elected bodies like city councils "adopt" WUI maps for their jurisdictions, and in some cases have altered the maps to take into account local conditions, especially where WUI boundaries might trigger building or vegetation management requirements in areas of lower risk.
Understanding this map:
- FIRESafe MARIN did not draw the maps.
- The WUI map is NOT a map of fire risk or hazard.
- WUI boundaries can change as development patterns and density changes.
- There is no universally accepted definition of WUI, and it can fluctuate or be defined differently in geograhic areas with different wildfire risk and hazard profiles.
- The maps may take into account political or local considerations.
- The WUI map shown at FIRESafe MARIN uses the boundary published at MarinMap.org by the County of Marin. It is not necessarily the most up-to-date or "official" map, and may not reflect the specific boundary adopted in all jurisdictions.
How to Determine if Your Home is in the WUI
Zoom in to the embedded Google Map below to see if your home is in the WUI. For building permit and planning issues, please verify with your local fire department and building/planning department.
MarinMap, a service provided by public agencies in Marin, provides a WUI lookup tool. Enter your address in the search bar to find your home.
MARIN COUNTY FIRE HAZARD SEVERITY ZONE (FHSZ) MAPS
Note: These maps are recommendations provided by CAL FIRE, and are not necessarily reflective of actual wildfire severity. Such zoning designations do not go into effect unless, and until, they are adopted by ordinance by local agencies. Local agencies are not required to report such zoning actions and CAL FIRE does not have a current list of local agencies that have adopted ordinances establishing Very High Fire Hazard Severity zones within their boundaries. In Marin, the adopted WUI boundary is equivalent to a State designated Very High Fire Hazard Severity zone.
For city and local agency data, please refer to county data above under Recommended LRA. View details at the CAL FIRE homepage.