Burn Site Evaluation following California Wildfires Thomas E. Spittler California Geological Survey
Concurrent Approaches I. Watershed-Scale Modeling A. B. USFS BAER & Rowe, Countryman & Story USGS Regression Models Cannon & others II. Site-Specific Evaluations CGS, this method
Rowe, Countryman & Story, 1949 Cannon & others, 2003, Old Fire.
The Site-Specific Approach I. Systematically Evaluate Post-Fire Risks II. Consistently Document Conditions III. Consider a Wide Range of Concerns I. II. Interior Subwatersheds Other Landuses (Hiking Trails) IV. Deliver Product to the Correct People
The Site-Specific Approach I. Systematically Evaluate Post-Fire Risks II. Consistently Document Conditions III. Consider a Wide Range of Concerns I. II. Interior Subwatersheds Other Landuses (Hiking Trails) IV. Deliver Product to the Correct People
Site # Date Reviewer Address Watershed/Drainage GPS location Quad Sec. , T. , R. , BL&M Photos: frames
Characterization Structure(s)/infrastructural element at risk: □ house □ major road □ trailer □ culvert □ business □ local road □ tank □ other
Watershed hillslope feature characteristics: a. □ small watershed □ large watershed □ colluvial hollow □ steep slope □ cut slope □ other b. size ac. c. slope (average and range) d. □ channel grade
Other Information • • Geology Geomorphology Percentage Slope Burned Burn Severity
Type of Potential Hazard • Flood • Sediment concentrated flood • Debris torrent • Possible future landslide • Other
Likelihood of Occurrence High (if impacted by a storm) Medium Low
Possible Risks to Lives Possible Risks to Property Potential for Engineered Mitigation
KOA Devore USGS Photo by Sue Cannon
The Site-Specific Approach I. Systematically Evaluate Post-Fire Risks II. Consistently Document Conditions III. Consider a Wide Range of Concerns I. III. Interior Subwatersheds Other Landuses (Hiking Trails) Other Types of Landslides IV. Deliver Product to the Correct People
The Site-Specific Approach I. Systematically Evaluate Post-Fire Risks II. Consistently Document Conditions III. Consider a Wide Range of Concerns I. II. Interior Subwatersheds Other Landuses (Hiking Trails) IV. Deliver Product to the Correct People
California Geological Survey Burn Site Evaluation Summary Fire Name: Bold where risks are Moderate or High Site At-risk Street number Feature address Houses 33683 & 33694 Green Valley Lane, Green Valley Lake 12 12 12 109 110 111 112 113 GPS location Latitude N N 34. 24119 House 701 Ridge Way Green Valley Lake N 34. 24043 House 33605 Falling Leaf Dr. Green Valley Lake Houses 33672 & 33668 Angels Dr. , Green Valley Lake House 33544 & 33536 Falling Leaf Dr. , Green Valley Lake N 34. 24000 N 34. 24032 N 34. 23949 Hazard Likeli- Longitude W hood W 117. 06797 Flood, debris torrent, future landslides High W 117. 06973 Flood, Sedconcentrated flood Risk to lives Risk to property fire pre-exist High Mod low low W 117. 07019 Flood, Sedconcentrated flood Mod low Mod W 117. 06893 Flood, Sedconcentrated flood low low W 117. 07165 Sedconcentrated flood, future slide Mod High Mod
REQUIREMENTS • Trained Technical Staff • Cooperation Between Agencies • Background Resources – Maps, Photos – Google Earth or ARC Explorer • High-Quality GPS • GIS Support
Conclusion Post-fire hazard assessments ► Watershed modeling ► Site-specific review • • Systematic evaluations Consistent reporting Considerations beyond floods Delivery to public safety officials
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