Wildfires in Florida

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Wildfires in Florida

• David T. Butry
• US Forest Service
• Marcia L. Gumpertz
• North Carolina State University
• Marc G. Genton
• Texas AM University
• Funding provided by USDA Forest Service

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Study SiteSJRWMD

• From 1996-2001
• 7249 small wildfires
• Arson25
• Accidents43
• Lightning32
• 53 large wildfires
• Arson17
• Accidents28
• Lightning55

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Size Distribution of Fires in SJRWMD 1981-2001
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Large Wildfires
Small Wildfires
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Wildfire Models

• Wildfire modeled as a function of
• Fuel type, fire cause, time, location
• Climate and weather at time of ignition
• Prescribed burning, time to respond to fire
• Landscape attributes, previous fire
• Three models estimated
• Area burned. Fires 1000 acres or less
• Area burned. Fires gt1000 acres
• Probability that a fire becomes larger than 1000
  acres.

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• Fire Characteristics (XF)
• Start time
• Start year
• Cause
• Climate/Weather (XC)
• Niño3
• KBDI
• Spread Index
• Buildup Index
• Humidity
• Wind speed
• Wind direction
• Management (XM)
• Response time
• Limited action fires
• Prescribed fire
• Includes current and lagged values, as well as
  neighboring current and lagged values

• Landscape Characteristics (XS)
• Population density
• Income
• Percent of population who have attended college
• Amount of road in section
• Distance to nearest fire department
• Landscape landcover/landuse
• Latitude longitude
• Fire district
• Previous wildfire
• Includes current and lagged values, as well as
  neighboring current and lagged values
• GIS hole

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KBDI Max Temp 24 h Precip Annual rainfall 0-800
Buildup Index Temp Humidity 24 h Precipitation Herbaceous stage 0 15 (low)        16 -- 40 (moderate)   41 80 (high)            81 200 (very high)  201 250 (extreme)
Spread Index Fuel moisture Wind Speed Precipitation Lesser vegetation 0 4 (low)    5 9 (moderate) 10 19 (high) 20 39 (very high) 40 100 (extreme)
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Spatial and Temporal Scales of Data

• Individual fire
• Location centroid of section
• Time of ignition

Spatial and Temporal Variables in Models

• Latitude and longitude (Albers projection)
• Year
• Time of day (morning, afternoon, evening,
  overnight)

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Lagged Variables

• Previous wildfire
• Section same or neighboring
• Year earlier in same year or in previous 12
  years
• Prescribed burning prior to the fire
• For hazard reduction
• Section same or neighboring
• Year earlier in same year or in previous 3
  years
• For silvicultural or other purposes
• Section same or neighboring
• Any time in this year or previous 3 years

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Model Specification

• Area burned
• Ln(Wildfire Size) X? ?,
• X may include lagged variables
• Probability of Large Fire

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ResultsSmall Wildfires, n7249, R2.19

• Factors related to greater area burned
• Response time up to 16 hours
• Limited-action fires (let burn)
• Spread index
• Palmetto-Gallberry, Grass, and Pine fuel types
• Arson ignitions (as opposed to lightning)
• Afternoon ignitions (as opposed to overnight)
• Area burned by wildfire in neighboring sections
  in the previous 1-12 years
• Previous non-hazard mitigating prescribed fire
  lagged up to 3 years

• Factors related to smaller area burned
• La Niña
• Humidity
• Hazard-mitigating prescribed burning in the
  current year
• Population density, up to about 70 persons per
  square kilometer (which is the median)
• Fire districts 10, 14, 16
• Smaller fires in 1999, 2000, 2001
• of water and wetlands in section
• of grasslands and upland forests in neighboring
  sections
• Interactions
• Several with KBDI

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Some Factors Related to Area Burned (Fires
1000 Acres)
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Effects of KBDI
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ResultsLarge Wildfires , n53, R2.73

• Factors Related to Greater Area Burned
• Spread index
• Wildfire in previous 12 years
• Percent of wetland in the section
• Population density
• Income
• 1998

• Factors Related to Smaller Area Burned
• Fuel type grass
• Arson and accidental ignitions, as opposed to
  lightning
• Fire District 12
• Interactions
• In GIS hole areas, percent of water in the
  section is positively related to large fire size

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Some Factors Associated with Area of Fire, Fires
gt 1000 Acres
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ResultsProbability that Area Burned will
Exceed 1000 Acresn7302, max rescaled R2.32

• Interactions
• Log odds increases with KBDI in upland forest
  sections but not in other types of land cover.
• Log odds decreases with hazard-reducing
  prescribed burning if response time is short, but
  not if response time is longer.
• If the response time is long, the log odds
  decreases as hazard-reducing prescribed burning
  increases in neighboring sections.

• Positive Relation
• La Niña
• Income
• Build-up
• Limited-action fires (let burn)
• Wind speed
• 1998
• Neighboring upland forest
• Negative Relation
• El Niño
• Upland forest
• Neighboring Urban areas

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Summary

• Lagged variables in space and time
• capture much of the spatial/temporal
• information, but not quite all of it.
• Models dont fit or predict nearly as well
• as Id like. Theres more to be done.
• Some encouraging results regarding
• ability to detect effects of management
• practices in section and neighbors.
• Continuing work on estimating magnitude of
• effect of prescribed burning -- using propensity
  scores.