How Communities Can Use This
Product to Enhance Their Floodplain
Management Program
The Potential of BLE Data
• 4.5-7.5 billion to provide flood mapping for
entire country
• $116 - $275 million to maintain accurate
and up-to-date flood maps annually
Flood Management State of the Union
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• Investment would drive down costs and suffering
and provide better tools for managing flood risk
• Costs affect individuals and businesses,
communities, states, and the federal government
• All taxpayers pay for consequences of flooding
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• Climate change
• Population growth
• US population has doubled since 1950 (161 million to
320 million)
• Projected to be over 380 billion in 2030 and 450
billion in 2050
Reasons for Increase Costs?
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0
100,000,000
200,000,000
300,000,000
400,000,000
500,000,000
1750 1800 1850 1900 1950 2000 2050 2100
US Population
Total Population Increase Poly. (Total Population)
• Maps won’t prevent flood from
occurring
• Essential tool in avoiding or minimizing
the damage to property, loss of life, and
communicating flood risk
Benefits of Flood Mapping
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• Without accurate flood maps local officials face
serious difficulties
• Guiding development away from hazardous areas
• Ensuring that development in or near the hazard area
is properly built and protected
• If potential flood prone area is not mapped
community has no tool to guide development
• 1997 – FEMA conducted a benefit-cost analysis
showing benefit to taxpayers of over $2 for every
$1 invested in flood mapping
• Buildings constructed in compliance with NFIP
building standards suffer 80% less damage
annually
Benefits of Flood Mapping (cont.)
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Purpose of Flood Maps
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Flood Hazard Information
Determine Flood Insurance Rates
Development Regulations
Flood Preparations for
those at Risk
Establish Zoning, Land Use, and
Building Standards
Infrastructure and Transportation
Planning
Flood Warning, Evacuation, and Emer. Management Planning
Flood Mitigation Loss Reduction
• 1968 Flood Insurance Act called for:
• Identification and publication of
information floodplain areas within 5 years
NFIP History
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• Establishment of flood-risk zones in all such areas
to be completed over a 15-year period following
passage of act
• Incorrect Assumption: Once initial flood maps were
published – no need for updating or republishing
• Early 2000s FEMA recognized
• Planned mapping had not been completed
• Flood map inventory started to become outdated
NFIP History (cont.)
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• Map Modernization (2004-2009): Goal to convert
nations paper maps to digital
• RiskMAP (2009-present): Lessons learned
• Providing only flood hazard boundaries perpetuates
the concept that flood risk in an “in” or “out”
proposition and doesn’t convey flood risks
• Effectiveness of communication with communities
during mapping process
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• $1.5 billion in avoided damages every year for
buildings constructed in compliance with NFIP
standards
• 22,000 communities participate in NFIP (317 In
LA)
• 5.5 million flood insurance policy holders
(501,851 In LA)
• Digital platform for flood maps and can be
integrated into federal, state, and local systems
NFIP Results
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CNMS in Louisiana
CNMS in Louisiana
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• 13 Parishes are
unmodernized
• Over 17,000 stream
miles non-NVUE
compliant
• https://msc.fema.gov/
cnms/
*ASFPM estimates between $4.5 – $7.5 billion dollars is
needed to accomplish these goals
What Remains to be Done?
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Complete Mapping for Communities without Maps
Update Communities with Maps but Incomplete Data
Update Communities to Reflect Changed Conditions
1
2
3
• Efficiencies in mapping using better technology
• Leveraging state and locally collected elevation
data
• Incenting better cost sharing overall
• Streamlining the geospatial processes and
management of data for flood mapping
• Increasing the flood insurance policy fee to
provide additional funds for flood mapping
Cost Savings
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What is Base Level Engineering?
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Base Level Engineering (BLE)
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Terrain
High resolution LiDAR (QL2 or better) data
required for BLE analysis
Hydraulics
Will the stream in question be able to
convey all the stormwater and runoff, and how
high will water get
Hydrology
What volume of water and when will the runoff
reach the stream
Floodplain Mapping
What areas of a community will be inundated based on engineering
analysis?
BLE Focus Areas
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BLE Models are Scalable
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BLE Products
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• Hydraulic Engineering Models10%, 4%, 2%, 1%, 1%+, 1%-, 0.2%
• Estimated Flood Extents10%, 1%, and 0.2%
• Estimated Water Surface Grids1% and 0.2%
• Estimated Flood Depth Grids1% and 0.2%
• Additional Purchased (R6)• Hazus – Level 2 Analysis
• Point file (Choke Points, Survey Support, and Update Areas)
• Base Level Engineering Report
• Other datasets can be produced, modeling is available
BLE - Best Available Data
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• The BLE results may be used in areas where no flood
hazard information is shown on your FIRM.
• Where BLE is similar OR more conservative it may be used
to provide Estimated Base Flood Elevations to residents
• Where BLE is smaller than current FIRM, BLE should NOT
be used to provide Estimated Base Flood Elevations
• BLE data complements FIRMs where they exist and current
flood coverage is minimal
• BLE information can be adopted and used as Best Available
Information by locals without a FIRM or Ordinance update
1. Estimating BFE
2. Engineering assessment for project
impact/permitting
3. Emergency management and disaster
response
4. Capital improvement planning and
infrastructure
5. Informing elevation certificates and LOMA
applications
BLE – Top 5 Uses at the Local Level
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BLE Online Viewer
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• Region 6 is currently
reformatting data for
upload to the viewer
• Ability to download
models and datasets
directly from the viewer
• Generate reports for
specific
points/addresses with
estimated depth of
flooding and estimated
BFEhttps://webapps.usgs.gov/infrm/estbfe/
• LaSalle and West
Feliciana moving
forward with BLE
data
• West Carroll Parish
has paper Flood
Information Guide
(FIG) as alternative
for BFE
determination in
Zone A
BLE Use in Louisiana
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LaSalle Parish
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• Little Watershed BLE
Completed in 2017
• Moved to Phase 2
• 30 miles Limited Detail
• 140 miles Approximate
• Incorporated 678 miles of
BLE
LaSalle Parish
BLE Study compared to Limited Detail Study
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LaSalle Parish
BLE – Before/After cleanup in sample 12 square-mile watershed
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West Feliciana Parish
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• West Feliciana Parish maps
dated 1979, not modernized
• Bayou Sarah Thompson BLE
completed in 2016
• Discovery completed in 2017
• West Feliciana Parish currently
using BLE for permitting and
BFE determinations
• Moved to Phase 2:
• 232 miles of limited detail
study
• 200 miles of BLE/Zone A to
be incorporated in FIRMs
• BLE results in City
of Denham Springs
showed drastic
reduction in flood
risk
• Urbanized areas or
areas with complex
H&H conditions may
not be accurately
captured
BLE Cautionary Tale
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• Acadia
• Allen
• Ascension
• Avoyelles
• Catahoula
• Concordia
• East Feliciana
• Evangeline
• Jackson
• Livingston
• Rapides
• St. James
• St. John the
Baptist
• St. Helena
• St. Landry
• St. Mary
• Tangipahoa
• Winn
Upcoming CTP BLE Workshops
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Late Summer/Early Fall
• FEMA Region 6 Resources
http://riskmap6.com/Resources.aspx
• CNMS Viewer and NVUE Report Generator
https://msc.fema.gov/cnms/
• BLE Viewer
https://webapps.usgs.gov/infrm/estbfe/
Links and Resources
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Questions?
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Jake Lesue, PE, CFMSenior Project [email protected]
Seth Bradley, PEProject [email protected]