FEMA Flood Mapping
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The presentation discusses FEMA flood mapping, focusing on the National Flood Insurance Program (NFIP) and its role in enabling property owners to purchase federal flood insurance. It highlights the transition from outdated flood insurance rate maps (FIRMs) to modern digital flood insurance rate maps (DFIRMs) for better accuracy and accessibility. The collaboration between FEMA and the County of Hawaii aims to improve mapping through updated technology and local GIS data.
FEMA Flood Mapping
- 1. FEMA Flood Mapping County of Hawaii Department of Public Works Engineering Division Presenter: Frank DeMarco, P.E. 1 of 11
- 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. 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. 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. 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. 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. 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. FEMA Flood Mapping 8 of 11 160 feet
- 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. FEMA Flood Mapping Waiakea Stream SFHAs, LOMRs & Engineer’s Work Maps 10 of 11
- 11. FEMA Flood Mapping 11 of 11 Questions?