Updating Erosion Updating Erosion Hazard Ratings in a Hazard Ratings in a
Post-fire AssessmentPost-fire Assessment
A GIS Tool for Soil Scientists
OverviewOverview
• Background
• Current Process
• Data
• My Toolset
• Anticipated Results
• Challenges
• Opportunities
BackgroundBackground
• California has devastating wildfires every year– Of the 4.8 million acres burned
this year so far, 1.26 million are in California
– 20 million acres of National Forest in California – 800,000 acres burned in 2008
• High vulnerability due to Mediterranean climate– Dry summers followed by wet
winters– Summer lightning storms with
little or no rain
• Many communities adjacent to forests (WUI – Wildland-Urban Interface)
• Fire is often just the beginning of concerns
Property
Watersheds
People
Post-fire assessments are handled by a BAER team
–Team is composed of interagency specialists
–Utilize data from multiple sources
–Requires field assessment as well as written report
Objective: To determine the need for and to prescribe and implement emergency treatments to minimize threats to life or property or to stabilize and prevent unacceptable degradation to natural and cultural resources resulting from the effects of a fire
Post-fire Assessments
• Need to begin immediately and completed within one week of containment
• Recommend and implement treatments to minimize damage
• Erosion, landslide prevention is a key element• Time is limited
Assessing the Potential for Erosion
• In California – Erosion Hazard Rating (EHR)– Developed jointly by the U.S. Forest Service
and the California Soil Survey Committee (1989)
– Used by many soil scientists, but not all– Some factors are subjective and require soils
expertise, familiarity with local geography– Usually computed in a spreadsheet
Computing EHR
• Erodibility Factors: Texture, aggregate stability
• Climate Factor: 2 yr, 6 hr precipitation
• Water Movement: Infiltration, depth to restrictive layer
• Slope and slope length
• Vegetative cover & distribution
Current Process – Part ICurrent Process – Part I
Pre-Planning
• Soil Scientists download soil surveys from Natural Resource Conservation Service website (http://soildatmart.nrcs.usda.gov)
• Sometimes have hardcopy reports
• Acquire burn severity maps
• Go to the field
• Electronic soil surveys from NRCS– Spatial data in coverage or shapefile format
with primary key field
Available Datasets
• Electronic soil surveys from NRCS– Tabular data in Access database
Available Datasets
Available Datasets
Available Datasets
• BARC – Burned Area Reflectance Classification– Produced for significant fires by USDA Forest
Service Remote Sensing Applications Center– Satellite derived burn severity data (raster
format)– Generally 4 classes: UNBURNED, LOW,
MODERATE, HIGH– Often used as a proxy for vegetative cover
Available Datasets
Both datasets are validated in the field
Burn Severity
Both datasets are validated in the field
Soil Type and Characteristics
Current Process – Part IICurrent Process – Part II
Post Assessment• Datasets are modified if needed• Elements for EHR are entered into spreadsheet• Spreadsheet is handed off to BAER Team GIS
specialist– merges the datasets – calculates the EHR for each soil/burn severity type– creates map of priority treatment areas
DataData
DataData
My ToolbarMy Toolbar
Export Table
My ToolbarMy Toolbar
Import Table
My ToolbarMy Toolbar
MergeDatasets
My ToolbarMy Toolbar
Create New EHR
Anticipated ResultsAnticipated Results
• A toolbar that can be added to ArcGIS Desktop software
• Documentation for standardizing data to be exported and imported
• Create interim merged dataset
• Create new EHR layer and post it to Table of Contents with standard color coding
ChallengesChallenges
• Making SSURGO certified soil data usable
• Extracting the necessary soil attributes and interpretations
• Integrating the BARC (raster) and the soil data (vector) : simplicity vs. speed
• Working with external tabular data (spreadsheet)
OpportunitiesOpportunities
• Develop Web Application– Adequate internet not always available– Datasets require manipulation - ??
• Create interactive form in the tool itself– Browsing– Attribute choices
OpportunitiesOpportunities
• Incorporate Slope Class– No treatment
on >60%– Between 30%
and 60% - aerial only
AcknowledgementsAcknowledgements
• Dr. Patrick Drohan, Penn State University, advisor
• Dave Young, Brad Rust, and Peter VanSusteren, USFS Soil Scientists
• Employees of the Shasta-Trinity National Forest
• Sue Cannon, USGS publication, http://pubs.usgs.gov/fs/2005/3106/pdf/FS-3106.pdf