Floodplain Management Association Conference, Rancho Mirage, CA

September 2015

Wildfire and Flood Hazards, Using GIS Tools to Assess Risk

• What advantages are there in looking at fire and flood hazards, together?

• What mitigation concepts work for fire and flood?

• What messaging or tools can we pull from fire risk assessment to apply to flood risk assessment, and vice versa?

Thoughts To Keep In Mind

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• Many of the same people who are interested in understanding flood risk are interested in fire risk assessment (just a selection below)

Flood and Fire - Who

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• Over 32% of the U.S. population lives in the wildland-urban interface (WUI) (USDA Forest Service, 2013)

• Wildfire activity for 2013 increased 50% above average of past 4 years, doubling burn area of 2012.

• Losses due to wildfire statistically result in 100% loss to the homeowner

Wildland Fire and Flood Risk• U.S. Population in SFHA ???

Closest stat was ASFPM’s 3% of population in a Coastal Flood Zone.

• “Record Flood” has been appearing more frequently in the news but are floods more frequent???

• $1B+ events flooding listed many times, fire only a few https://www.ncdc.noaa.gov/billions/events

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FIRE FLOOD

Flood Rate Map – 1% annual chance hazard

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Flood Risk Map – Economic Losses

• Risk Analysis is:• Predictive• Assesses current situation / ground conditions• Data intensive• Results that can be used to take action

Risk Reports

• Regional models

• National level data sets

• 30-m Grid Cell or use national level data

• Mostly summarized at Zip Codes we offer Parcel or Address

• Underwriting, point-of-sale renewal of insurance – Not incident command and action

Fire and Flood GIS Risk Factors

• Community or HUC-8

• Stream-by-Stream, localized data

• 2-ft contour accuracy, LiDAR points

• Interpreted for individual locations

• Flood insurance and community floodplain management, mitigation planning and disasters

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FIRE FLOOD

• Roof Type and Configuration

• Attached structures (especially wooden)

• Exterior Wall Type• Foundation• Construction Type/Style• Fireplaces• Maintenance Condition• Dwelling Type• Method of HVAC• Garages/Carports• Freeboard

Fire and Flood GIS Risk Factors• Lowest Finished floor

Elevation• Occupancy Type• Replacement Cost /

Content cost• Flood protection / Design

level• Foundation type• Attached structures• Year built• Square footage• House ignition zone

radius

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FIRE (when evaluating a property) FLOOD (Hazus UDF)

Freeboard vs Ignition ZoneHistorical Riverine Home

Before

After

Do these actions swap one natural hazard risk

for another?

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Freeboard Achieved

House Ignition Zone not achieved

Fire Factors:• Fuel / Vegetation

• Size and Shape• Arrangement• Moisture Content (dead or alive)

• Fire History• Terrain

• Slope• Weather

• Wind• Precipitation

Fire and Flood GIS Risk Factors

Regression Equation:

• You know these…

• Terrain

• Precipitation

• Drainage Area

• Impervious Surface

• Slope

• … more factors

• Hydraulics for the details

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FIRE FLOOD

U.S. Population Living Near WUI

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• Fire History• Title: Fire History• Source: U.S. Geological Survey• Note: Fire patterns within landscape

are based on interactions between vegetation dynamics, fire spread, fire effects, and spatial context.

Data Sources

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• Precipitation• Title: United States Average

Annual Precipitation• Source: National Atlas of the

United States

Data Sources

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• Fuel / Type of Vegetation• Title: 13 Anderson Fire Behavior

Fuel Models• Source: U.S. Geological Survey

Data Sources

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• LandCover• Title: National Land Cover

Dataset• Source: USGS• Note: Categories include

agriculture, barren, developed, herb, shrub, sparse, tree, and water

Data Sources

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• Slope (Elevation)• Title: National Elevation

Dataset• Source: USGS NED

Data Sources

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• Wind• Title: National Wind Resource

Assessment• Source: US Department of

Energy• Note: Ratings are taken by wind

power density

Data Sources

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Factor Influence (%)*

Vegetation 20

Fuel 20

Fire History 20

Precipitation 20

Wind 10

Slope 10

Methodology

* These rankings may be adjusted based on user input

Factor Attributes Low (1) Medium (2) High (3) Very High (4)

Vegetation Type 1 X

Vegetation Type 2 X

Vegetation Type 3 X

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Vegetation

Fuel Model

Slope

Methodology

LOW RISK HIGH RISK

MORE FUELLESS FUEL

LOW RISK HIGH RISK

STEEP SLOPEGRADUAL SLOPE

LOW RISK HIGH RISK

DRY BROADLEAF TREESWET LOW VEGETATION

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Wind

Fire History

Precipitation

Methodology

LOW RISK HIGH RISK

SHORT FIRE RETURN INTERVALLONG FIRE RETURN INTERVAL

LOW RISK HIGH RISK

LOW PRECIPITATIONHIGH PRECIPITATION

LOW RISK HIGH RISK

HIGH WIND SPEEDSLOW WIND SPEEDS

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Wildland Fire Model Output

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Image Courtesy of Yavapai County Flood Control District, AZ

Risk Report Web Application

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• Rancho Cucamonga worked with CAL FIRE on Wildland Fire Risk Maps for the City

• Permit / Development / landscaping guidelines

• One more step to combine with flood risk?

http://www.cityofrc.us/cityhall/fire_district/high_fire_hazard_area.asp

Interactive Map Viewer: http://regis.cityofrc.us/Wildlandinterface/default.htm

Wildland Fire Hazard Risk Areas

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Show Me My House

Photo realistic visualization helps make the message personal

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Freeboard or Depth GridHow much water up against your home?

30-90-120 ftFuel Risk Rings

200-ft home ignitionzone

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Used to seeing single natural hazard focused Mitigation Action Suggestions

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• Combine a risk assessment for many hazards?

Multi-HazardMitigationActions

Fire Hazard

Erosion Potential

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Post-Fire Flood Risk• Fire decreases

infiltration and increases runoff

• Allowing more precipitation to reach the ground

• Soil-water storage is reduced

• Fire eliminates fine roots that bind soils together

• Potential for sediment transport

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Graphic and content from Victoria Stempniewicz NAU Thesis: Evaluating Erosion Risk Mitigation Due to Forest Restoration Treatments Using Alluvial Chronology and Hydraulic Modeling

Post-Fire Flood Risk - Schultz

| Floodplain Management Association Conference, Rancho Mirage, CA, September 201528Photos from azdailysun.com

Pamphlet -https://www.azdeq.gov/function/programs/download/adwr-wildfire_insurance.pdf

• Landslide / mudslide post-fire risk probability analysis

Post-Fire Flood Risk

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http://landslides.usgs.gov/hazards/postfire_debrisflow/2015/20150617lake/

• Fire and Flood risk do go together.• Share common data layers• They impact each other either• Groups starting to look at the

combined hazard with post-fire/flood/landslide/debris flow risk

• Are there lessons we can learn from discussing fire risk in the flood hazard world and vice versa?

• Can mitigation options address more than one natural hazard and what does it take to get the conversation focused like that?

Please continue to consider

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Questions?

Flames from the Rocky Fire approach a house on July 31 in Lower Lake, California. Justin Sullivan / Getty Images