Flood Hazard Mapping and the National Flood Insurance

Program

Michael Buckley, PE

Dewberry

Background

Professionally involved in the NFIP since 1975. Currently VP for Dewberry’s Water Resources Consulting Services

29 years with FEMA; Deputy Assistant Administrator for FEMA’s NFIP and Mitigation Programs (2004-2009)

Led the $1 billion initiative to modernize the Nation’s flood maps

Dewberry: mid-size full service A&E with strong expertise in hazard identification, risk assessment, GIS technology and post flood surveys and analysis

Offices located throughout the United States

Dewberry has had contracts to do flood mapping since 1974

Outline

• What’s behind the Science • Look at New Levee Analysis • FEMA Risk MAP program • Mapping Provisions in BW12 • Summary

Riverine Analyses - Overview

Hydrology = determination of runoff due to rain from upland areas to a certain point

Hydraulics = how high the runoff will flow in the channel / overland

Riverine Hydrology - Statistical

• Approx. 6,000 stream gages nationwide • 1.2 M out of 3.5 M miles mapped

• Gages record flow in rivers and elevation of flow

Riverine Hydrology - Statistical

• Period of record allows statistical analyses to determine 10-, 50-, 100-, 500- year recurrence interval peak flows

• Longer the period of record, higher the reliability

• Assumption: Trends in past will continue into future

Riverine Hydrology – Models

• Data intensive • Rainfall • Land Use • Terrain • Structures (dams,

culverts, bridges) • Need to calibrate • Could be reliable but

high cost

Riverine Hydrology – Regression

• Regression equations developed using statistical data

• Inputs are limited leading to simple analysis

• Lower Reliability • Limitations

• Not urban • Drainage area

Riverine Hydraulics

• Model flow in channels, canals, overbank areas (including urban areas)

• Channel & overbank specifics determine height of flow

• 1 Dimensional vs. 2 Dimensional Flow

Source: http://www.xpsoftware.com/wp-content/uploads/Flooding-W bi df

Mapping

Using BFEs the SFHA is plotted on the FIRMs using ground elevation data (LIDAR where available)

Levels of Riverine Analyses:

Study Type Purpose What is Mapped

Bridges / culverts

Modeled?

Multi-Frequency

Approximate Low Population 100-yr No No

Limited Detailed Moderately Developed

100-yr; BFEs Yes* No

Detailed Densely Populated

100-yr & 500-yr, BFEs, Floodway

Yes Yes

Riverine Analyses – Reliability

• Hydrology ⁻ Level of detail ⁻ Land Use ⁻ Rainfall

amount & distribution

⁻ Transferring gage data to other locations

⁻ Available gage records

• Hydraulics ⁻ Level of detail ⁻ Calibration ⁻ Unobstructed flow ⁻ Channel specifics

and migration ⁻ New Culverts and

Bridges not included in models or maps

Coastal Analyses

Elements of coastal analyses ⁻ Stillwater Elevations (SWEL) – ADCIRC ⁻ Waves: setup, surface, runup ⁻ Erosion: beaches and dunes

Ensemble of many storms, not just 1 event More complicated & costly than riverine analyses

Coastal Analyses - Reliability

• Calibration helps • Limited historical storm

data • Erosion/shoreline change • Storm defenses • Change in land use • Use of representative land

cover • Wave characteristics

Future Development / Trends & Sea Level Rise

• Special Flood Hazard Areas are determined for existing conditions (land use and sea levels) and historical climate and data trends

• Conditions in the future can be dramatically different than they are today

Flood Mapping Summary

• Science is not exact • Reliability varies in hydrology &

hydraulics • Reliability dependent on data • Big return on LIDAR investment • Data does not account for change in

future trend and future development • Cost is a consideration

Flood Mapping of Levees Accredited levee system When a levee was found to be in compliance with 44 CFR 65.10, the flood hazard was mapped to be contained within the levee system.

Non-accredited levee system However, areas with non-accredited levees were mapped as if the levee system provided no flood hazard reduction (“without levee” analysis).

Overview of the New Levee Analysis and Mapping

FEMA is replacing the former levee analysis and mapping approach with a suite of alternative procedures. The new procedures have undergone an extensive process of scientific review and public input

Overview of LAMP Approach

There are five procedures detailed in the LAMP Final Approach Document.

Natural Valley

Sound Reach

Freeboard Deficient

Overtopping

Structural-Based Inundation A system can be broken up into multiple reaches in order to analyze the flood risk in its vicinity. Community involvement is key

1 System ↓

Multiple Reaches

Benefits of the Approach

• Increased stakeholder engagement

• Increase refinement of flood hazard identification associated with non-accredited levee systems

• FEMA will use the new approach to produce: • FIRMS

• Flood Insurance Studies (FIS)

• Related products for communities and tribes impacted by non-accredited levee system

Visit the following webpage to access additional information regarding FEMA’s revised Levee Analysis and Mapping Procedures:

http://www.fema.gov/final-levee-analysis-and-mapping-approach

For More Information on Levees

What is Risk MAP?

Risk MAP (Mapping, Assessment, Planning) builds on the Map Modernization program and strengthens local ability to make informed decisions about reducing risk through more reliable maps, risk assessment tools, and outreach support.

Risk MAP Vision & Goals

Risk MAP will deliver quality data that increases public awareness and leads to action that reduces risk to

life and property Address gaps in flood hazard data Measurably increase public’s awareness & understanding Lead effective engagement in Mitigation Planning Provide an enhanced digital platform Align Risk Analysis programs and develop synergies

Additional Map Products

34

0.2% Depth(500-Year)

8.9 ft

4.3 ft

1.7 ft

FEMA FLOOD MAPPING BUDGET

$-

$50

$100

$150

$200

$250

$300

$350

2009 2010 2011 2012 2013

POLICY FEEAPPROPRIATIONM

ILLI

ON

S

BW12 Mapping Provisions SEC. 215 TECHNICAL MAPPING ADVISORY COUNCIL 20 Members – Federal Agencies, State Agencies, CTP,

Professional Organizations Recommend : Data Accuracy & Quality Ease of use & distribution Performance metrics Future conditions: Climate, Sea Level, Future Development Risk assessment modeling Delegation to State and Local Partners

BW12 Mapping Provisions SEC. 216 NATIONAL FLOOD MAPPING PROGRAM

Existing and Future Populated Areas 100 & 500-Yr

Residual Risk

Use Most Accurate Topo

Coastal Inundation

Land Subsidence, Coastal Erosion, Changing Lake Levels

Outreach and Notification

Authorized Annual Funding - $ 400 Million

BW12 Mapping Provisions

SEC. 217 SCOPE OF APPEALS

SEC. 218 SCIENTIFIC RESOLUTION PANEL

SEC. 219 REMOVAL OF LIMITATION ON ST CONTRIBUTIONS

SEC. 221 INTERAGENCY COORDINATION STUDY

SEC. 226 FLOOD PROTECTION STRUCTURE ACCREDITATION TF

BW12 Mitigation Provisions

Consolidates FMA, RFC, SLR

Makes SRL Permanent

Allows direct grants to Individuals

Limits Planning Grants to $50K/$25K

Allows up to 100% funding for SRL

Authorizes $100 million (FY14)

What can communities do?

Engage with FEMA throughout the Risk MAP process Contribute data and resources to improve reliability Know where the highest risks are Communicate with property owners Make reducing your risks a priority Require new buildings in high risk zone BFE ++ Talk with your state about mitigation funding options