Fire Hazard Severity Zones: Russian River Basin, California, 2001

Given the limitations and age of this data, it has very limited utility. Examination of this data suggests that little effort was made to standardize zoning procedures between ranger units. There are cases where ranger units that might be expected to have similar hazard characteristics appear to be much different in terms of FHSZs. For example, there are ranger units zoned exclusively as Very High while an adjacent unit has a variety of zones of different ratings. There are also cases where ratings change abruptly at ranger unit boundaries. These inconsistencies are a direct result of a lack of procedural standardization, and could be due to different long-term planning periods, different interpretation of fuel models, or the level of detail used to map the various zones.

The gross inconsistencies in the data are obvious from even a cursory examination of the statewide FHSZ map. The fact that there was no effort to standardize the mapping effort or review the data for accuracy suggest that the data be used with extreme caution.

Finally, the zones are designed to give an average hazard rating for the area. This does not necessarily define the exact conditions for all areas within the zone. Variations in fuels, slope, weather, as well as factors not considered in this exercise such as aspect, elevation, and air stability will influence hazard conditions at actual locations within each zone. For an individual structure, the risk of damage from fire also depends on site-specific factors such as access, water supply, clearance, and characteristics of the structure. Since statewide hazard zoning cannot capture these factors, it should not be used as a measure of the risk faced by individual structures. Supplemental Info: "Instructions for Zoning Fire Hazard Severity in State Responsibility Area in California", by Clinton B. Phillips, December 1983