Evaluating the Quality of a Wildfire Defensible Space with Airborne LiDAR and GIS Jason Harshman GEOG 596A Capstone Proposal August 2015 1.
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Evaluating the Quality of a Wildfire Defensible Space with Airborne LiDAR and
GIS
Jason HarshmanGEOG 596A Capstone Proposal
August 2015
1
Presentation Outline
• Background
• Project Goals
• Study Area
• Methodology
• Initial Results
• Future Plans
2
CAL FIRE
Background• Prolonged drought in California has greatly increased wildfire risk• Year-round wildfire season for much of California• 11,000 structures lost to wildfires between 2003-2013 in
California• Over $30 million in damages in 2013• CAL FIRE annual budget over $200 million
Wildfire near a San Marcos, CA home, May 2014 (Anthony Carrasco/San Diego Union-Tribune)
Wildfire near a San Marcos, CA home, May 2014 (Sean M Haffey/San Diego Union-Tribune) 3
What is a defensible space?• Prevent structure ignition• Requires vegetation maintenance surrounding a structure• 100 feet from a structure’s edge• May extend beyond 100 feet• Requirements can vary between different jurisdictions• Split into 2 zones
Illustration of a defensible space (CAL FIRE). 4
Defensible Space0 to 30 feet (Zone A)
•“Free and Clear”
•Remove tree canopy overlapping structure
•Remove highly flammable vegetation
30 to 100 feet (Zone B)
•Reduce vegetation density
•Reduce ladder fuels
•Requirements vary depending on slopeIllustration of Zone B requirements (CAL FIRE).
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Project Goals
• Analyze the quality of a structure’s defensible space
• Quality equates to how well a structure’s defensible space follows
defensible space regulations
• Use LiDAR data to map vegetation and terrain surrounding structures
• Develop a general methodology that can be applied to other locations
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Project Location• Sonoma County, CA• 77% of county wildfire responsibility is CAL FIRE• 20% is rated “Very High” for wildfire risk
Regional location of Sonoma County, CAWildfire responsibility areas in Sonoma County, California
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Locate a Study Area• Identify a test location for analysis of a small group of structures
o CAL FIRE responsibility area
o 1-mile of the last 10 years of fires
o “Very High” wildfire hazard areas
o “Maximum” wildfire threat areas
o Remove conservation/sensitive land and public land
o Majority conifer and shrub land cover
o Area must have structures
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Study Area
Proposed Study Area Sample selection of structures
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LiDAR Data
• Airborne LiDAR and Orthoimagery collected in late 2013
• Currently largest coverage of public domain LiDAR data within
California
• Classified point cloud of LiDAR (http://sonomavegmap.org)
• Structure footprints polygons derived from the LiDAR also
available
Source Sonoma County Vegetation Mapping and LiDAR Program (http://sonomavegmap.org/)
Collected by Watershed Sciences, Inc. (WSI)
Altitude 900 AGL
Laser Pulse Rate 105,000 Hz
Field of View 30°
Average Point Density 2.88 p/m2
Horizontal Accuracy Not provided
Vertical Accuracy ~6 cm
LAS ClassificationsUnused (0), Unclassified (1), Ground (2), High Vegetation (5), Buildings (6), Noise (7), Water (9), Excluded (11)
LAS Format 1.2
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Methodology Overview
• Create several surface datasets from the LiDAR
• Separate analysis for Zone A and Zone B
• Average results from Zone A and B into final score
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Surface Datasets• Create several surface datasets from the LiDAR
Dataset Acronym Resolution FunctionData Type
Interpolation Method Source
Digital Elevation Model DEM 2 Feet
Ground elevation surface Grid
Natural Neighbors Triangulation
Ground classified points, all returns
Digital Surface Model DSM 2 Feet
Terrain elevation surface Grid
Natural Neighbors Triangulation First return points
Canopy Height Model CHM 2 Feet
Relative height from the ground Grid N/A DSM-DEM
Slope N/A 2 FeetSlope of ground surface Grid N/A DEM
Tree Canopy Surface Model CSM 2 Feet
Canopy elevation surface Grid Simple
High vegetation classified points, first return
Building Surface Model BSM 2 Feet
Building elevation surface Grid Simple
Building classified points, all returns
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Zone A• Calculate amount of vegetation coverage within Zone A
Zone A30 feet
Get count within
structure footprints
Calculate % of structure with overlap
Zone A Value
Calculate canopy
overlap of structures
BSM - CSMReclassify positive
values to 1
Get CSM count within
Zone A
Calculate % of CSM in Zone A
Calculate canopy
coverage within Zone
A
Average values
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• Determine if tree canopy overlaps structure footprint
Zone B• Determine if distance between tree canopy is sufficient
Zone B30-100 feet
Reclassify slope to 1, 2,
3
Create individual tree data
with FUSION
Plot locations in
GIS
Buffer based max
crown widths
Euclidean Distance of
crowns
Reclass distances of 10, 20, 30 ft to 1,
2, 3
Distance Reclass minus Slope
Reclass
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Zone B
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Slope % Reclass Tree Distance Reclass
1 (10 feet) 2 (20 Feet) 3 (30 Feet)
1 (0-20%)0 1 2
2 (20-40%)-1 0 1
3 (40%+)-2 -1 0
• Slope Reclass - Distance Reclass matrix
Zone A + Zone B
• Average Scores together
• Scores closer to 0 suggest a better quality defensible space
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0.0 1.0
High Quality
Poor Quality
Zone A Initial Results• Values range from 0.026 to 0.528
• Lower value = higher quality of defensible space
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Zone A Initial Results
Lowest Zone A score Lowest Zone B score
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Zone B
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Zone A Zone B
Poor quality Zone B
• Identify vegetation coverage that exceed minimum requirements Zone A Zone
B
High quality Zone B
Discussion
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• Validity of overall methodology
• Zone A initial results promising
• Need quality LiDAR for quality surface datasets
• Surface datasets key to analysis
Justin Sullivan / Getty Images
Future Plans
• Refine methodology
• Scale-up analysis
• Diversify landscape types
• Analysis of other location(s)
• Build a tool or set of tools?21
CAL FIRE
Timeline
22
August
Refine Methodology
ID Other Locations & Gather Data
Submit Abstract
AAG Annual Meeting
Perform
Analysis
October
January
March2016
2015
May
596B
Submit Write-
up
References• CAL FIRE. (2013). Wildfire activity statistics. Sacramento, CA: California Department of Forestry and Fire Protection.
Retrieved from http://www.fire.ca.gov/downloads/redbooks/2013Redbook/2013_Redbook_Final.pdf• CAL FIRE. (2015a). Defensible space and hardening your home Retrieved from
http://www.readyforwildfire.org/docs/files/CALFIRE_Ready_Brochure.pdf • CAL FIRE. (2015b). Emergency fund fire suppression expenditures. Sacramento, California: California Department of
Forestry and Fire Protection. Retrieved from http://www.fire.ca.gov/fire_protection/downloads/SuppressionCostsOnepage.pdf
• Amy Hubbard. (2014, September). California burns through $209-million wildfire budget, taps $70 million more. Los Angeles TImes Retrieved from http://www.latimes.com/local/lanow/la-me-ln-california-exhausts-budget-wildfires-20140930-story.html
• San Diego Union-Tribune. (2014). Day 2: San diego county fires. Retrieved from http://www.sandiegouniontribune.com/photos/galleries/2014/may/14/bernardo-fire-14-contained/
• Alexandra D. Syphard, Teresa J. Brennan, & Jon E. Keeley. (2014). The role of defensible space for residential structure protection during wildfires. International Journal of Wildland Fire, , 1165-1175. doi:10.1071/WF13158
• Philip E. Dennison, Simon C. Brewer, James D. Arnold, & Max A. Moritz. (2014). Large wildfire trends in the western unitedstates, 1984–2011. Geophysical Research Letters, 41, 2928-2933. doi:10.1002/2014GL059576
• Susan M. Stein, Sara J. Comas, James P. Menakis, Mary A. Carr, Susan I. Stewart, Helene Cleveland, Lincoln Bramwell and Volker C. Radeloff. (2013). Wildfire, wildlands, and people: Understanding and preparing for wildfire in the wildland-urban interface. (). Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.
• Robert J. McGaughey. (2014). FUSION/LDV: Software for LIDAR data analysis and visualization Retrieved from http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf
• US Forest Service.Smokey bear. Retrieved from http://www.smokeybear.com/design-resources.asp23
Acknowledgements
Doug Miller
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Questions?
25
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