FEMA’s Coastal Risk MAP study for Georgia - … · FEMA’s Coastal Risk MAP study for Georgia...

FEMA’s Coastal Risk MAP study

for Georgia

Georgia Association of Floodplain Managers: 8th Annual Conference, Lake Lanier, GA March 13, 2013

2

Agenda

Welcome/Introductions

Project Overview

Schedule

Technical Presentation

Questions and Answers

Nassau County, FL

3

Introductions Risk MAP Project Team

• FEMA Region IV

• BakerAECOM, LLC (Production and Technical Services (PTS) contractor)

Michael Baker Corp.

AECOM,

Taylor Engineering, Inc.

Marea Technology, LLC

University of Central Florida

University of Notre Dame

Oceanweather, Inc.

Worldwinds, Inc.

Open Introductions

• (―Hi, I am Scott from ….‖)

4

FEMA Region IV Coastal Flood Risk Studies in Florida

5

Your flood risk changes over time.

We chose your counties to review to more accurately

define risk and account for significant development

in the counties.

• Significant flood risk from coastal storms (hurricanes, tropical

storms, nor'easters)

• Increase in population and development since current effective

FIRMs published

A complete, current picture of your coastal flood

hazards and risks will help you better:

• Plan for the risk

• Take action to protect your communities

• Communicate the risk to your citizens

Why Surge Analysis for GA Was Updated

6

Your risk is better defined through

• Updated guidelines

Atlantic Ocean and Gulf of Mexico Guidelines Update (2007)

Sheltered Water Report (2008)

PM 50 Limit of Moderate Wave Action (LiMWA) (2008)

• Updated elevation data (topographic data and aerial

imagery)

• New climatological data based on recent storms

• Newer coastal hazard methodologies (developed since

Hurricane Katrina)

• Improvement in Geographic Information System (GIS)

technologies to improve coastal mapping accuracy

Why Surge Analysis for GA Was Updated (Cont’d)

7

Risk Mapping, Assessment, and Planning (Risk MAP) Overview

FEMA works with you and other communities to

develop flood risk products and flood hazard maps

that are:

• Based on the best available data from community and latest

technologies

• Conducted by watershed (riverine)

• Conducted by affected communities and counties (coastal)

• Strengthened by partnerships

You can use Risk MAP tools and data to:

• Create or improve your Hazard Mitigation Plans

• Make informed decisions about development, ordinances, and

flood hazard mitigation projects

• Communicate with citizens about flood risk

8

Program Product Comparisons

Traditional NFIP products are

regulatory and subject to statutory

due-process requirements.

New Risk MAP products are non-

regulatory and are not subject to

statutory due-process requirements.

DFIRM Database

Traditional Regulatory Products Non-Regulatory Products

9

Coastal Flood Risk Study Timeline

10

Base Flood Elevation (BFE) on a FIRM includes four components:

• Storm surge stillwater elevation (SWEL)

• Wave setup

• Wave height above total SWEL

• Wave runup above storm surge elevation (where present)

All applied to an eroded beach profile (when applicable)

The above components are computed through

• Terrain processing and profile erosion

• Storm surge study for SWEL determination

• Coastal hazard analysis

Basic Elements of a Coastal Flood Risk Study

11

Project Work Plan

Work assigned to BakerAECOM as PTS:

• Perform coastal storm surge and wave height analyses

for GA and NEFL counties

• Develop coastal floodplain boundary delineations and

produce work maps

• Provide work maps to GA

12

Projected Schedule

Production Runs: August 2013

Statistical Analysis: September 2013

Overland Wave Analysis: December 2013

Flood Hazards Work Maps: September 2014

• BakerAECOM gives work maps to GA CTP

13

Extent of Coastal Surge Study

NEFL Georgia

Coastal Counties

Bryan

Duval Camden

Flagler Chatham

Nassau Glynn

St. Johns Liberty

Volusia McIntosh

Interior Counties

Clay Brantley

Putnam Charlton

Effingham

Long

Wayne

14

Approach - Storm Surge SWEL

Return Period Analysis JPM-OS 2%, 1%, 0.2% Annual Chance

Tide Gage Analysis 50%, 20%, 10% A.C.

SWEL

0

2

4

6

8

1 10 100 1000

Su

rge

(m

)

Return Period (years)

5663jpm

stochastic

0

2

4

6

8

1 10 100 1000

Su

rge

(m

)


5667jpm

stochastic

0

2

4

6

8

1 10 100 1000Su

rge

(m

)Return Period (years)

6251jpm

stochastic

0

2

4

6

8

1 10 100 1000

Su

rge

(m

)


6492jpm

stochastic

High-Resolution

Bathymetry / Topography

Mesh

Storm Surge Modeling

Winds

Waves Water Levels

Storm Forcing Hurricane Tracks

JPM-OS: Joint Probability Method - Optimum Sampling

15

Initial Results

Model Mesh Development

• Developed seamless topographic and bathymetric data

surface (Digital Elevation Model [DEM])

• Developed SWAN+ADCIRC Mesh

• Tasks completed in parallel

Storm Climatology

Validation Storm Selection

Validation Comparisons

16

Seamless Topographic and Bathymetric

Data Surface (DEM) Development

LIDAR

National

Elevation

Dataset

GEOphysical Data

Management

System

Electronic

Navigational

Charts

USACE/SJRWMD

Hydro Survey

Geo

Database

Shoreline

Seamless

Topographic/

Bathymetric

Data Surface

Convert

to

NAVD88

NAVD88: North American Vertical Datum of 1988

17

LIDAR and Bathymetric data

18

LIDAR LIDAR Coverage (Cont’d)

19

LIDAR Coverage (Cont’d)

20

LIDAR Coverage (Cont’d)

21

NOS Data, Different Survey Dates and Data Extents

Bathymetric Data Coverage (Cont’d)

22

Same Area, Different Data Sources, Survey Dates, and Data Extents

Bathymetric Data Coverage (Cont’d)

23

SWAN+ ADCIRC Model Mesh

Development

• SWAN+ADCIRC Model

Finite element model

Uses unstructured,

triangulated mesh

Node spacing set to

accurately represent

topography/bathymetry

Created ―feature arcs‖ to

represent elevated or

depressed features (i.e. roads

or channels)

24

DEM to SWAN+ADCIRC Mesh: Step 1

25


26


27


28

SWAN+ADCIRC Mesh

29

SWAN+ ADCIRC Model Mesh

Development (Cont’d)

30

Initial Results

Mesh Development

• Development of Seamless Topographic and

Bathymetric Data Surface

• Development of ADCIRC Mesh

Storm Climatology



31

Tropical Storms:

1940 - 2010

Passing within

175 nm of

Jacksonville

Typically

Category 1 or less

at landfall

Storm Climatology: Storms in Study

Area

32

Tropical Storms:

1842 - 1939

Passing within

175 nm of

Jacksonville

Instances of

greater than

Category 3

storms

Storm Climatology: Storms in Study

Area (Cont’d)

33

Tropical Cyclone Tracks and

Parameters

Landfalling storms:

1940 – 2010

Central Pressure < 980 mb

Category 1 or greater

Limited activity in study area

34


Parameters

Analysis of important storm

parameters (considered random in

JPM-OS analysis)

• Central pressure

• Radius to maximum winds

• Forward speed

• Storm heading

• Holland’s B (shape parameter)

35

• Optimized set of 178 storms

• Final SWAN+ADCIRC simulations apply storms


Parameters (Cont’d)

36

• Comparison of reference set and optimal set at specific

comparison locations

• Results indicate optimal set adequately reproduces

reference values

2%-annual-

chance event

1%-annual-

chance event


Parameters (Cont’d)

37

Initial Results

Mesh Development




Storm Climatology



38

Validation Storm Selection:

Significant Surge Events 1950-1959

Landfalling, bypassing,

exiting storms that

passed near study area

39




exiting storms that


40




exiting storms that


41




exiting storms that


42




exiting storms that


43




exiting storms that


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Significant Surge Events

0 25 50 miles

Study Area

Northern

Limit

0 10 20 miles

0 20 40 miles

Study AreaSouthern Limit

NOAA stations with water level (WL)

data

45

NOAA National Buoy Data

Center (NDBC) stations with

wave data

0 50 100 miles

Study Area

Southern Limit

Study Area

Northern Limit


Significant Surge Events (Cont’d)

46

Criteria Sorting of Storms

1. Local

Landfall

2. Significant WL

Difference

3. WL Data Availability

(> 3 Stations)

4. Wave Data Availability

(2 or more stations)

Cleo

Dora

David

Chris

Edouard

Tammy

Fay

Dora (5.91 ft)

David (5.55 ft)

Jeanne (4.22 ft)

Tammy (4.07 ft)

Fay (3.99 ft)

Frances (3.85 ft)

Gabrielle (3.82 ft)

Floyd (3.8 ft)

Ophelia (3.04 ft)

Abby (2.93 ft)

Irene (2.92 ft)

Bertha (2.62 ft)

Bob (2.44 ft)

Erin (2.43 ft)

Cleo (2.35 ft)

Dennis 99 (2.24 ft)

Frances (15)

Charley (14)

Jeanne (14)

Ophelia (9)

Tammy (9)

Dennis 99 (8)

Edouard (8)

Floyd (7)

Irene (7)

Fay (6)

David (5)

Frances (5)

Ophelia (5)

Tammy (5)

Fay (5)

Jeanne (4)

Edouard (3)

Charley (3)

Chris (2)

Dennis99 (2)

Floyd (2)

Irene (2)



47

Criteria Sorting of Storms

1. Local

Landfall

2. Significant WL

Difference

3. WL Data Availability

(> 3 Stations)

4. Wave Data Availability

(2 or more stations)

Cleo

Dora

David

Chris

Edouard

Tammy

Fay

Dora (5.91 ft)

David (5.55 ft)

Jeanne (4.22 ft)

Tammy (4.07 ft)

Fay (3.99 ft)

Frances (3.85 ft)

Gabrielle (3.82 ft)

Floyd (3.8 ft)

Ophelia (3.04 ft)

Abby (2.93 ft)

Irene (2.92 ft)

Bertha (2.62 ft)

Bob (2.44 ft)

Erin (2.43 ft)

Cleo (2.35 ft)

Dennis 99 (2.24 ft)

Frances (15)

Charley (14)

Jeanne (14)

Ophelia (9)

Tammy (9)

Dennis 99 (8)

Edouard (8)

Floyd (7)

Irene (7)

Fay (6)

David (5)

Frances (5)

Ophelia (5)

Tammy (5)

Fay (5)

Jeanne (4)

Edouard (3)

Charley (3)

Chris (2)

Dennis99 (2)

Floyd (2)

Irene (2)



48

Five validation storms

selected

• Hurricane Dora (1964)

• Hurricane David (1979)

• Hurricane Frances (2004)

• Tropical Storm Tammy (2005)

• Tropical Storm Fay (2008)



49

Initial Results

Mesh Development




Storm Climatology



50

Validation: Tides

Tide validation based on

comparisons to NOAA

stations with tidal

constituent data

51

Validation: Tides; Amplitude

52

Validation: Historical Storms;

Hurricane Dora

53

Maximum Modeled Water Levels from Hurricane Dora — Nassau and Duval Counties, FL


Hurricane Dora (Cont’d)

54


Hurricane Dora (Cont’d)

55


Hurricane David

56


Hurricane Frances

57


Tropical Storm Tammy

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Tropical Storm Fay

59

Validation: Historical Storms; All

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Validation: Historical Storms; Waves,

Hurricane Frances

61

Validation: Historical Storms; Waves,

Hurricane Frances (Cont’d)

62


Waves, Height

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Validation: Summary

Validation completed for tides and five

historical storms

Demonstrated model capability to

reproduce water levels and waves in

project area

Comparisons to available data showed

reasonable agreement for water levels and

waves

64

Upcoming Work

Production runs (with synthetic storms) using

supercomputer

Frequency analysis for 0.2%-, 1%-, 5%-, 10%-,

20%-, and 50%-annual-chance storms

Overland wave analysis

Work map production

Cedar Key

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Open Discussion – Questions?

Technical questions about data applied…?

Technical questions about methodology…?

Technical questions about model validation or

application…?

General questions about project schedule?

General questions about outreach activities?

Other questions?

66

Coastal Flood Risk Study Team Contacts

Tucker Mahoney, FEMA Coastal Flood Risk Study Lead

• [email protected]

• 770-220-5626

Michael Delcharco, BakerAECOM Project Manager


• 904-731-7040

Dick Wild, BakerAECOM Coastal Outreach Lead


• 703-317-6222

mailto:[email protected]



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