FEMA Flood Mapping

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Nation Flood Insurance Program (NFIP)

Current Flood Insurance Rate Maps (FIRMs) & Special Flood Hazard Areas (SFHA)

FEMA’s Map Modernization Program & Digital Flood Insurance Rate Maps (DFIRMs)

DFIRMs for Hawaii County

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FEMA Flood Mapping

  1. 1. FEMA Flood Mapping County of Hawaii Department of Public Works Engineering Division Presenter: Frank DeMarco, P.E. 1 of 11
  2. 2. FEMA Flood Mapping  Presentation Overview  Nation Flood Insurance Program (NFIP)  Current Flood Insurance Rate Maps (FIRMs) & Special Flood Hazard Areas (SFHA)  FEMA’s Map Modernization Program & Digital Flood Insurance Rate Maps (DFIRMs)  DFIRMs for Hawaii County 2 of 11
  3. 3. FEMA Flood Mapping  Nation Flood Insurance Program (NFIP)  Created by Congress in 1968.  Enables property owners in participating communities to purchase Federal flood insurance.  Nationally, ~21,000 communities participate, ~5.5 million structures insured, worth ~$1.1 trillion in coverage.  County of Hawaii, ~4,000 structures insured ~$900,000 in coverage. 3 of 11
  4. 4.  The NFIP is based on an agreement between the community and the federal government:  Community adopts and enforces a floodplain management ordinance (e.g., Hawaii County Code Chapter 27 http://www.hawaiicounty.gov/lb-countycode#countycode) to reduce future flood risks to new construction in Special Flood Hazard Areas (SFHA).  Federal government makes Federal flood insurance available to the community.  NFIP has three parts: Floodplain Management, Insurance & Mapping (i.e., Flood Insurance Rate Map). FEMA Flood Mapping 4 of 11
  5. 5. FEMA Flood Mapping  Official community flood map that delineates the special flood hazard areas (SFHA), or 1- percent-annual chance flood areas (aka. 100- year floodplains).  Current FIRMs are based on 1970’s mapping technology.  Single layer of map information.  Separate paper maps for individual communities.  Difficult and costly to change and distribute. 5 of 11  Flood Insurance Rate Map (FIRMs)
  6. 6. FEMA Flood Mapping  Upgrade to GIS based digital flood insurance rate map (DFIRM) format.  Create 1 seamless community DFIRM.  Incorporate Letters of Map Revisions.  Convert the vertical reference datum for flood elevation data (NGVD 29 to NAVD 88). For State of Hawaii, LTD.  Most Map Modernization projects were completed by 2010.  In 2003, FEMA initiated a national five year $1 billion Flood Map Modernization program to upgrade the paper FIRMs. 6 of 11
  7. 7. FEMA Flood Mapping  County protested/appealed FEMA’s 2008 & 2011 Preliminary Digital Flood Insurance Rate Maps (Pre-DFIRMs)  Insufficient time for review (i.e., 90-days):  113 panels.  Four volume Flood Insurance Study (110 pages on mapping basis & 384 flood profiles).  SFHA georeferencing onto the satellite imagery does not comply with FEMA’s horizonal accurancy criteria.  Map Scale: 1:500 is 19 feet; 1:1000 is 38 feet and 1:2000 is 45.6 feet. 7 of 11
  8. 8. FEMA Flood Mapping 8 of 11 160 feet
  9. 9. FEMA Flood Mapping  Feb 2013, FEMA & County agree to improve the Pre-DFIRMs (Technical Cooperative Partnership)  FEMA agreed to use 2010 NCRS imagery as the base map and update Pre-DFIRM base on County’s GIS data.  Using ESRI ArcGIS Ver. 10, County agreed to:  Digitize (*.tif or*.png) the current FIRMs, Letter of Map Revisions (LOMRs) and Engineer’s LOMR work maps (work maps).  Georeference SFHA’s, LOMRs & work maps to the 2010 NRCS imagery.  Deliverables based on 4 - 100 working days. 9 of 11
  10. 10. FEMA Flood Mapping  Waiakea Stream SFHAs, LOMRs & Engineer’s Work Maps 10 of 11
  11. 11. FEMA Flood Mapping 11 of 11 Questions?
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