LRA Legislation Factsheet - Flipbook combined - Flipbook - Page 6
FHSZ Frequently Asked Questions
General
How do the Fire Hazard Severity Zone Maps differ from California Public U琀椀li琀椀es Commission
(CPUC) High Fire Threat District Maps?
The California Public U琀椀li琀椀es Commission (CPUC) sponsored map, known as "CPUC High Fire
Threat District Map” (HFTD), includes similar factors as those in the FHSZ maps, however the CPUC
HFTD Map is designed specifically for iden琀椀fying areas where there is an increased risk for u琀椀lity
associated wildfires. As such, the CPUC map includes fire hazards associated with historical
powerline-caused wildfires, current fuel condi琀椀ons, and scores areas based on where fires start, as
opposed to where poten琀椀al fires may cause impacts.
How are Fire Hazard Severity Zones determined?
CAL FIRE used the best available science and data to develop, and field test a model that served as
the basis of zone assignments. The model evaluated the probability of the area burning and
poten琀椀al fire behavior in the area. Many factors were included such as fire history, vegeta琀椀on,
flame length, blowing embers, proximity to wildland, terrain, and weather.
What new data will be included in the new model, and how does this differ from the previous
model?
A 2 km grid of climate data covering the years 2003-2018 is being used in the update. The previous
model used stock weather inputs across the state to calculate wildland fire intensity scores. The
updated model will adjust fire intensity scores based on the most extreme fire weather at a given
loca琀椀on, considering temperature, humidity, and wind speed. In addi琀椀on, ember transport is being
modeled based on local distribu琀椀ons of observed wind speed and direc琀椀on values instead of using
a generic buffer distance for urban areas adjacent to wildlands.
