Changes to FEMAMapping

John Grace, CFMCoastal Engineer - FEMA Region 1 - Boston

March 14, 2014 – The Soil and Water Conservation Society – Winter Conference

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Program Overview Risk MAP

• Mapping – Flood hazard and risk identification

• Assessment – HAZUS and other risk assessment tools

• Planning – Hazard mitigation planning and HMA grants

Risk MAP Vision• Deliver quality data• Increase public awareness of

flood risk • Encourage local/regional

actions that reduce risk

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Risk MAP Project TimelineDiscovery

Meeting Project Kickoff Flood Study Review

Resilience Meeting

Final CCO Meeting

3-5 Year Process

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FEMA Mapping

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Detailed Study – Coastal Analysis

Stillwater Level (storm surge) + Wave Set-up

Overland Wave Propagation

Wave Runup and Overtopping

Primary Frontal Dune

Coastal analysis - includes 4 main components:

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Detailed Study – Stillwater Level (SWEL) with Gage Data

Return period gage analysisLinear interpolation between gage points

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Detailed Study – Wave Setup Numerically determined at each coastal transect

Determining factors Average nearshore slope [depth of wave breaking to SWEL] Deepwater significant wave height

SWEL + Wave Setup = Total Water Level (TWL)

Areas where floodplain is restrictive, wave setup is removed and SWEL is mapped Constrictions such as low bridges Narrowing of the floodplain

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Detailed Study – Overland Wave Propagation

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LiMWA (Limit of Moderate Wave Action)

Areas subject to wave heights greater than 1.5 feet, but less then 3 feet.

Standard flood insurance requirements apply.No regulatory requirement. (Rhode Island requires V zone regulations)Defines the coastal A zone.

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Runup and Overtopping

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Primary Frontal Dune

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FLOOD RISK PRODUCTS

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Flood Risk Products These products are intended to help communities better understand and

communicate flood risk

Non - Regulatory

All of these products are GIS based

The following flood risk products may be available:

• Changes Since Last FIRM• Flood Risk Assessment• Contributing Engineering Factors• Wave Height Grids • Flood Risk Report

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Changes Since Last FIRM

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• Annualized flood losses are displayed on the Census Block Data

• Aimed at depicting general flood loss areas

CITY OF REVERE250288

Flood LossVery Low

Low

Medium

High

Very High

Flood Risk Assessment

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Contributing Engineering Factors

• Provide insight into the factors behind the increase or decrease in the flood hazard areas

• Can prove to be useful for planning and mitigation measures

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Wave Height GridsProvided for 1%annual chance floods

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Flood Risk Report

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WEB LINKS

Preliminary Data• www.fema.gov/preliminaryfloodhazarddata

Effective Data (including Future Effective)• msc.fema.gov

National Flood Insurance Program• www.floodsmart.gov

Flood Insurance Reform Act• www.fema.gov/flood-insurance-reform-act-2012