Fire Hazard Severity Zone Map

History of Fire Hazard Severity Zones

FHSZ’s came because of legislation arising out of lessons learned from major wildland fires. In 1980, the Panorama Fire, which began in San Bernardino County and was pushed by strong Santa Ana winds burned 28,800 acres, destroyed 325 structures, and experienced 4 fatalities. In the aftermath, the Governor passed Public Resource Code 4201, which mandated CAL FIRE to develop FHSZ’s in the State Responsibility Areas. Eleven years later, the Tunnel Fire in 1991, which is more widely known as the Oakland Hills Fire, devastated a community that was not previously identified as a hazard zone because it was in a Local Responsibility Area. This fire was significant because it became the deadliest fire to date. Although it only burned 1,520 acres, it destroyed 2,900 structures and was attributed to the death of 25 people.

This event prompted legislators to adopt AB-337 also known as the “Bates Bill”. This bill mandated the Director of CAL FIRE to assess FHSZ’s in Local Responsibility Areas and make recommendations to the local agencies for “Very High” Fire Hazard Severity Zones.

In 2021, new legislation, Senate Bill 63 (Stern), now requires the adoption of all three FHSZ classes in the Local Responsibility Area. Previously, only the “Very High” FHSZ’s were required for adoption in Local Responsibility Areas.

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FHSZ Types

Public Resource Code 4202; The State Fire Marshal shall classify lands within State Responsibility Areas into Fire Hazard Severity Zones. Each zone shall embrace relatively homogeneous lands and shall be based on fuel loading, slope, fire weather, and other relevant factors present, including areas where winds have been identified by the department as a major cause of wildfire spread.

Government Code 51178; The State Fire Marshal shall identify areas in the state as Moderate, High, and Very High Fire Hazard Severity Zones based on consistent statewide criteria and based on the severity of fire hazard that is expected to prevail in those areas. Moderate, High, and Very High Fire Hazard Severity Zones shall be based on fuel loading, slope, fire weather, and other relevant factors including areas where winds have been identified by the Office of the State Fire Marshal as a major cause of wildfire spread.

The Fire Hazard Severity Zone map reflects “hazard,” not “risk”. The map is like flood zone maps, where lands are described in terms of the probability level of a particular area being inundated by floodwaters, and not specifically prescriptive impacts. “Hazard” is based on the physical conditions that create a likelihood and expected fire behavior over a 30 to 50-year period without considering mitigation measures such as home hardening, recent wildfire, or fuel reduction on efforts. “Risk” is the potential damage a fire can do to the area under existing conditions, accounting for any modifications such as fuel reduction projects, defensible space, and ignition resistant building construction.