1st Annual Hawaii Island HIGICC Geospatial Expo

FEMA Flood Mapping

County of Hawaii

Department of Public Works

Engineering Division

Presenter: Frank DeMarco, P.E.

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FEMA Flood MappingPresentation 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

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FEMA Flood MappingNation 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.

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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

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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)

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.

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FEMA Flood MappingCounty 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

FEMA Flood Mapping

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160 feet

FEMA Flood MappingFeb 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

FEMA Flood MappingWaiakea Stream SFHAs, LOMRs & Engineer’s Work Maps

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FEMA Flood Mapping

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Questions?