1. FEMA Region III Coastal Hazard Analyses and DFIRMs Update
Jeff Gangai – Dewberry
Robin Danforth – FEMA Region III

2. Introduction State of Effective Coastal Studies
Why a coastal restudy is needed?
Elements of a Coastal Flood Insurance Study
Ongoing FEMA Region III Storm Surge Modeling Effort
Overland Wave Analysis Components
Preliminary coastal tasks to be performed for coastal counties.

3. State of Effective Coastal Study
Topographic data used for modeling and mapping date back to the Mid-1970’s and mid-1980’s from USGS maps
SWELs go back to a 1978 VIMS study for the Chesapeake Bay and Tidal Gage Analysis on the Atlantic Coast.
Coastal studies date back to late 1970’s and early 1980’s
Wave height determined with NAS method.
Erosion analysis not performed
Wave setup not accounted for
Limited WHAFIS nad/or wave runup modeling performed

4. Why a coastal restudy is needed?
New Guidelines need to be implemented
Atlantic Ocean and Gulf of Mexico Guidelines Update (2007)
Sheltered Water Report (2008)
PM 50 Limit of Moderate Wave Action (LiMWA) (2008)
To update base data such as topographic dataset and aerial imagery to high resolution products and seamless Digital Elevation Model (DEM)
To utilize newer coastal hazard modeling methodologies developed during the FEMA Mississippi Coastal Restudy
To take advantage of higher performance numerical modeling
To take advantage of improvement in GIS technologies to allow for more accurate and detailed FIRMs

5. Hurricane Isabel Sept 18, 2003 Recorded Surge Levels:
7.5 ft/2.2 m Chesapeake Bay Bridge-Tunnel
8.3 ft/2.5 m at Gloucester Point

6. Hurricane Isabel, Chesapeake Bay

7. FEMA Region III Study Area
Four states plus District of Columbia
Five metropolitan areas
Complex coastal geomorphology
Delaware River/Bay system - Tidal up to Trenton, NJ square mile bay - Strategic shipping and military port
Chesapeake bay - Third largest estuary in world ,000 miles of tidal shoreline - Major shipping, seafood and military ports
VA: 30 counties with shoreline exposed to the Atlantic Ocean and the Chesapeake Bay
MD: 16 counties (Atlantic Ocean and Chesapeake Bay)

8. Elements of a Coastal Flood Insurance Study
BFE on a FIRM includes 4 components:
Storm surge stillwater elevation (SWEL)
Wave setup
Wave height above total stillwater elevation
Wave runup above storm surge elevation
All applied to an eroded beach profile
The above components are computed through:
Terrain processing and profile erosion
Storm surge study for SWELs determination
Coastal Hazard Analyses
Floodplain boundaries, flood hazard zones and LiMWA are then mapped on FIRMs

9. FEMA RIII Storm Surge Project Organizational Chart
FEMA Project Officer
Robin Danforth
DHS Region III
US Army Engineer Research
and Development Center
Advisory Board
R. Luettich (UNC-CH)
B. Ebersole (USACE-CHL)
J. Smith (USACE-CHL)
K. White (USACE-CRREL)
K. Galluppi (RENCI)
M. Powell (DE)
R. Wise (NAP)
USACE Storm Surge
Program Manager
J. Hanson (USACE-FRF)
J. Roughton (USACE-FRF)
D. Nelson (USACE-CRREL)
Project Support
J. Gangai (Dewberry)
E. Drei-Horgan (Dewberry)
B. Batten (Dewberry)
Storm Specification
P. Vickery (ARA)
V. Cardone (Oceanweather)
A. Cox (Oceanweather)
Modeling System
B. Blanton (RENCI)
P. Vickery (ARA)
V. Cardone (Oceanweather)
A. Cox (Oceanweather)
R. Luettich (UNC-CH)
H. Friebel (NAP)
E. Devaliere (UNC)
C. Fulcher (UNC)
J. Atkinson (ARCADIS)
H. Roberts (ARCADIS)
GIS Database
K. Gamiel (RENCI)
B. Blanton (RENCI)
M. Forte (USACE-FRF)
J. Yuan (ECSU)
Bathy / Topo
J. Miller (NAP)
C. Rourke (NAP)
M. Hudgins (NAO)
P. Moye (NAO)
M. Schuster (NAB)
J. Scott (NAB)
M. Forte (USACE-FRF)
M. Blanchard (RENCI)
L. Stillwell (RENCI)

10. Return Period Analysis
Approach
Storm Forcing
Extratropical Wind Fields
Hurricane Tracks
High-Resolution
Bathy / Topo
Mesh
Storm Surge Modeling
Winds
Waves
Water Levels
Return Period Analysis
JPM-OS Hurricanes
EST Extratropicals
Flood Levels
10-, 50-, 100-, & 500-year

11. Extra-Tropical Storm Forcing
Selection based on water levels at 7 stations
Total of 31 historical storms
Kinematic reanalysis of all wind fields
Empirical Simulation Technique (EST) used for return period calculations
To include sampling at 5 tidal stages
Return Period
Analysis

12. Nor’Ida November 2009 Norfolk, VA Remnant of Hurricane Ida
Added to extratropical data set
Sewells Point, VA
6-ft Surge
Delaware

13. Tropical Storm Forcing
Record of 20 hurricanes in 60 years insufficient for 100- and 500-yr computations
Synthetic storm set used to develop landfall frequencies and hurricane parameters
Joint Probability Method for return period analysis
Demonstrated validity with comparisons to historic data
Modeled Tracks
VA/DE/NJ
Central Pressure
Difference
Heading

14. Development of a Topo/Bathy Digital Elevation Model (DEM)
10 m DEM
DEM covers: NJ DE MD VA
Portions of PA
Delaware Bay
Chesapeake Bay and main tributaries
Atlantic Ocean

15. High Resolution Bathymetry and Topography
Data assimilation through USACE districts
Use Lidar for topography where available
Region divided into 20 tiles
Consistent bathy/topo surface with 10-m horizontal resolution
10-m Resolution
Region III DEM
Geographic Tiles

16. ADCIRC Grid
Grid allows to capture complex coastal morphologies and provide high resolution of shoreline features, embayment and estuaries
Expected grid resolution 50 m at shore/high developed areas, 1-2 km offshore
ADCIRC will be coupled with the 2D wave model SWAN
The coupling of the two models will allow to compute starting wave conditions and wave setup for the overland wave analyses

17. Storm Surge Modeling System
Wind and Pressure Fields
TC96 PBL Hurricane Model
OWI Extratropical Reconstructions
Water Levels
ADCIRC Coastal Circulation
and Storm Surge Model
Waves/ Radiation Stress
WaveWatch III Basin Scale Waves
SWAN Coastal Waves
Radiation Stress
WW3
Coupling
SWAN

18. Storm Surge Project Status
Accomplishments:
Bathy/Topo Inventory
Draft DEM
Establish JPM Approach
Winter Storm Selection and Windfield Develop.
Prototype Modeling System
Validation Tools –
Interactive Model Evaluation and Diagnostics System
Ongoing:
DEM Review
ADCIRC Mesh Development
Models Calibration and Validation
Synthetic Storms Development
Future Tasks:
Production
Frequency Analysis

19. Coastal Hazard Analyses Components
Transect layout
Field Reconnaissance (land use, obstructions, shoreline conditions, structures)
Starting wave conditions (wave height and period) from 2D wave modeling eliminating the need for limited fetch analysis
Wave setup from 2D wave modeling
Primary Frontal Dune (PFD)
Dune erosion: 540 sqft rule
WHAFIS modeling for overland wave height computation
2% Wave Runup
All above analyses will be performed with the Coastal GeoFIRM tool
Coastal GeoFIRM
Technology facilitates higher resolution while reducing costs
Framework allows preliminary tasks to be performed parallel for surge modeling
Benefits:
Accelerated study timeframe
High resolution results
Improved mapping accuracy
Repeatability
Less subjectivity

20. Transect Placement
Shoreline in High and Low Population Density Areas

21. Field Reconnaissance

22. Overland Wave Hazard Modeling
WHAFIS 4.0
Profile elevation
1% SWELs
Starting wave conditions
Wave Setup
Obstruction cards (OF, IF, BU, VE, MG)

23. Coastal Hazard Modeling and Mapping Workshop
Wave Runup
FEMA G&S 2007 requires the use of the 2% runup vs. the mean runup computed prior to 2007
Mild-sloping beaches, bluffs and cliffs
Coastal Structures:
Will structure survive the 1% event?
Is structure certified?
Modeling of integral structure vs. fail structure to determine higher hazard
Runup on structures limited to 3 ft on top of the structure’s crest w/overtopping possible AO Zone
Methods:
Runup 2.0, TAW, ACES, SPM
Page 23

24. Added Detail with GIS

25. Mapping

26. Limit of Moderate Wave Action (LiMWA)
FEMA Procedure Memorandum No. 50, 2008
At present not a regulatory requirement
No Federal Insurance requirements tied to LiMWA
CRS benefit for communities requiring VE Zone construction standards in areas defined by LiMWA or areas subject to waves greater then 1.5 ft.
Potential of additional 650 points

27. Limit of Moderate Wave Action (LiMWA)
Defined by the area subject to wave action with waves greater than 1.5 ft in height

28. LiMWA – mapped example

29. Project Schedule Spring 2010 Summer 2010 Fall 2010 Spring 2011
Complete DEM
Surge Model validation Initiate Surge production
Complete Surge production and return period analysis GIS site fully populated
Complete Overland Wave Analysis
Complete Hazard Mapping
Hurricane Isabel September 2003

30. Web/GIS Interface Public outreach site under construction
Storm Selection
Public outreach site under construction
GIS interface to results for stakeholders
Google-earth displays of storm tracks, model output fields and return periods
Inundation Levels
Maximum Wave Heights

31. Questions?