Fire Hazard Severity Zoning FHSZ in California: A Hundred Million Acres of Challenge

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Fire Hazard Severity Zoning(FHSZ) in
CaliforniaA Hundred Million Acres of Challenge

• --Dave Sapsis
• dave.sapsis_at_fire.ca.gov

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Why?

• Recurring Problem
• State Law Requirment
• 1981 Ayala PRC for SRA lands
• 1992 Bates Govt. code for local areas

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What?
FHSZ 1985 v.4

• Definitions
• Hazard physical conditions that can cause
  damage
• Fire Hazard (burn probability) x (fire behavior
  )
• Risk expected damage
• Risk requires lots more information!

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Definitions (cont.)
FHSZ 1985 v.4

• Fire Hazard Severity Zones
• represent areas of variable size ranging from 20
  acres in urbanized areas to at least 200 acres in
  wildland areas, with relatively homogeneous
  characteristics regarding expected burn
  probability and potential fire behavior
  attributes based on climax fuel conditions over a
  30-50 year time horizon.

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Why Re-Map Now?

• New WUI building codes tied to hazard maps
• Old maps have issues

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Model Methods

• Statewide (100 M acres)
• Uniform data and techniques applied everywhere
• No jurisdiction influence on zones
• No new funding

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Create Wild Land and Urban Zones
S T A R T
Torching Tree surface
Flame Score
Slope (0-20, 20)
Convert to Vector and Eliminate zones less than
200 acres
Flame Score by Zone (Flame_score_p)
Score Urban Zones
Score Wild Land Zones
Flame Class
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Model Structure

• Two Steps
• 1. Zoning 2 types
• 1) Wildlands
• 2)Developed/urban and adjacent Non-flammable
  areas
• 2. Scoring

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Developed Area Hazard

• Created in conjunction with UC Berkeley Center
  for Forestry
• Combination of Veg mapping, Density derived from
  census, and blocks of small parcels

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Developed Zoning

• Using 2006 parcel data
• Clusters of 20 acre minimum, with average maximum
  parcel size 2 acres
• Most areas much smaller parcels

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Developed Hazards

• Footprint aggregated from parcels, minimum size
  20 ac
• Wildland inholdings inside footprint must be gt20
  ac

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Wildland Zoning

• Computer generated polygons
• Aggregated on slope and vegetation (200 ac)
• Slope lt or gt 20
• principal Life Forms
• Grass, brushlands
• woodlands,
• conifer, conifer woodland

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Wildland Scoring

• Individual cells are scored based on expected
  chance of burning and the potential fire behavior
  for that site (including reception of firebrands)

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Wildland Scoring

• Flame Class Brand Class FHSZ Score
• Contiguous Areas of similar score are averaged to
  create zone scores

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Wildland Scoring

• Zones are classified into three ranks Moderate,
  High, and Very High
• FHSZ Class

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Developed Hazards

• Footprint aggregated from parcels, minimum size
  20 ac
• Wildland inholdings inside footprint must be gt20
  ac

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Developed Scoring

• Urban Burnability
• Footprint mapped for vegetation/fuel density
  (2005/06 TM imagery)
• Vegetation density used as measure of burnability
  or penetrability to wildland fire

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Developed Scoring

• FHSZ ranks within the footprint are a function
  of
• adjacent wildland score
• firebrand reception
• vegetation density

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Maps fixed to parcels
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Seamless Map

• Add developed FHSZ to wildland FHSZ to create
  seamless map
• SRA non-ranked zones are recoded to Moderate
• Zone edges snapped to parcels
• 5 ac parcels are not split
• SRA window defines FHSZ
• LRA window defines areas for Bates recommendations

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Map Status

• SRA maps validated, in hearing review, AOL review
  to follow with Title 14 adoption Jan 1, 2008
• LRA DRAFT maps in review, target delivery of
  reccommendations beginning Jan 1, 2008

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General Project Information

• http//frap.cdf.ca.gov/projects/hazard/fhz.html
• Project background and links to authorizing
  statutes
• Link to draft maps for download (PDF and JPG)
• Both proposed SRA and DRAFT LRA-VH
• GIS data files (shapefiles, by county)
• Review Guidelines
• Comprehensive methods slideshow with notes
• Links to Building Code info

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WUI Building Code Info

• http//osfm.fire.ca.gov/UWIBS.html

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What Have I Learned?

• A man who carries a cat by the tail learns
  something he can learn in no other way.
  --Mark Twain

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Model Support Resources

• Powerpoint file with notes for each slide
• Various model methods documentation
• Original review background 1/07
• SRA hearing workbook
• LRA model background and issues
• Consultation (email, phone, meetings where
  necessary)
• Regional Model SME
• Me