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

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.

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

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

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

Hurricane Isabel, Chesapeake Bay

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 - 782 square mile bay - Strategic shipping and military port Chesapeake bay - Third largest estuary in world - 11,000 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)

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

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)

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

Extra-Tropical Storm Forcing Selection based on water levels at 7 stations Total of 31 historical storms 1975-2009 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

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

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

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

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

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

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

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

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

Transect Placement Shoreline in High and Low Population Density Areas

Field Reconnaissance

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

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

Added Detail with GIS

Mapping

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

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

LiMWA – mapped example

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

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

Questions?