MAPPING HAZARDS AND RISK

FEMA FLOOD MAPPING PROCESS

ICON Engineering, Inc.


  • Stormwater and Floodplain Management Specialists
    • Floodplain Modeling/Mapping
    • Hydrologic and Hydraulic Analysis
    • Master Plans, Stream Stabilization, Restoration and Water Quality
  • Locally Based (Centennial, CO)
    • Colorado & Front Range Clientele
    • Consultant to City of Boulder & CU-Boulder
    • Very Active Since 2013 Floods
  • FEMA DFIRMs & Letters of Map Revision (CLOMR/LOMR)
    • FEMA/CWCB DFIRM Contractor
    • UDFCD LOMC’s - Over 400+ Cases Reviewed

ICON Engineering, Inc.


Craig Jacobson, PE, CFM

  • 18 Years Consulting Experience
  • Hydrology and Hydraulics, Master Planning Manager
  • LOMR/CLOMR, MT2s, Modeling Preparation & Review
  • Other
    • Instructor:  ASFPM Certified Floodplain Manager (CFM)
    • Instructor:  UWRI FEMA Letters of Map Change Course
    • CASFM Organization:   Outreach and Training Co-Chair

Eben Dennis

  • GIS Coordinator
  • Web Mapping Developer
  • Nerd

National Flood Insurance Program


A voluntary program based on a mutual agreement between the Federal government and the local community.

In exchange for adopting and enforcing floodplain management regulations, Federally-backed flood insurance is made available to property owners throughout the community.

National Flood Insurance Program


1968 National Flood Insurance Act

  • Transferred costs from the taxpayers to floodplain property owners
  • Provided financial aid
  • Guide development away from flood hazard areas

1973 Flood Disaster Protection Act

  • More encouragement for participation!
  • Flood insurance required for federally-backed loans
  • Limited federal disaster assistance for communities without flood insurance

NFIP Participation

National Flood Insurance Program


Biggert-Waters Reform Act 2012 / Homeowners Flood Insurance Affordability Act 2014

  • Reform ending subsidies for insurance
  • Mapping on a watershed basis

1994 National Flood Insurance Reform Act

  • Community Rating System (CRS)
  • Increased flood coverage maximum
  • Strengthened mandatory purchase
  • Mitigation Grant Program

 National Flood Insurance Program 

MAPPING

INSURANCE

REGULATIONS

Components of a Flood Insurance Study 

Flood Insurance Study Report (FIS)

  • Discussion of Flooding History
  • Technical Analyses
  • Flood Discharges & Frequencies
  • Flood Profiles
  • Mapping Information

Components of a Flood Insurance Study 

Flood Insurance Rate Map (FIRM)

  • Floodplain Inundation Limits
  • Flood Insurance Zones
  • Base Flood Elevations
  • Hydraulic Cross-sections
  • Mapping Information

Floodplain Regulation 

Basis of Regulation

  • 1% annual chance flood 
  • 100-year event
  • Floodway
    • Theoretical boundary

“...means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot {or stricter local standard}.”

Floodplain Mapping Standards 

Topography

Aerial Mapping

LiDAR

Survey

Hydrology

The quantity of water that must pass a given point

Hydraulics

The configuration and “roughness” of the channel and adjacent overbank area that must carry that water

 

var nfhl = L.tileLayer.wms("https://hazards.fema.gov/gis/nfhl/services/public/NFHLWMS/MapServer/WMSServer", {
    layers: '4',
    format: 'image/png',
    transparent: true
    
}) .addTo(map);

Limitations

Topography

  • Age
  • Level of detail
  • Fixed in time
  • Erosion
  • Deposition

Limitations

Hydrology

  • Design Assumptions
  • Rainfall Intensity
  • Storm Duration
  • Land Use Projections
  • Soil Moisture
  • Man-made features
    • Dams
    • Detention Ponds

Limitations

Hydraulics

  • Vegetation 
  • Aggregation
  • Degradation
  • Erosion
  • Debris
  • Man-made features
    • Bridges/Culverts
    • Flood debris
    • Human response to flooding

Text

City of Boulder - Twomile Canyon Creek

Next Steps........?

Questions?

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