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 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: 1. Storm surge stillwater elevation (SWEL) 2. Wave setup 3. Wave height above total stillwater elevation 4. Wave runup above storm surge elevation All applied to an eroded beach profile The above components are computed through: 1. Terrain processing and profile erosion 2. Storm surge study for SWELs determination 3. Coastal Hazard Analyses Floodplain boundaries, flood hazard zones and LiMWA are then mapped on FIRMs

Ongoing FEMA Region III Storm Surge Modeling Effort Current stillwater elevations (SWELs) on FIRMs date back to (few updates made in early-1990s) and were computed using a tidal gage analysis or the VIMS model SWELs will be updated for 50 coastal counties covering approx miles of shoreline State-of-the art modeling setup by using ADCIRC soft coupled with the 2D wave model SWAN Obtain updated 10%, 2%, 1% and 0.2% annual chance stillwater elevations, wave setup and wave conditions for nearshore open-coast and back-bay shorelines

Study Objectives Develop, validate and prepare a storm surge modeling capability for the assessment of future inundation risks in the FEMA Region III area Based on post-Katrina modeling technologies High resolution bathy/topo mesh Define tropical / extratropical storm hazards Integrated flood risk modeling system Verification of model accuracy Compute and assess the Region III flood hazard values for 10-, 50-, 100- and 500-yr return periods GIS database and display capacity

FEMA Project Officer Robin Danforth DHS Region III Project Support J. Gangai (Dewberry) E. Drei-Horgan (Dewberry) B. Batten (Dewberry) USACE Storm Surge Program Manager J. Hanson (USACE-FRF) J. Roughton (USACE-FRF) D. Nelson (USACE-CRREL) 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) 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) 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) FEMA RIII Storm Surge Project Organizational Chart US Army Engineer Research and Development Center US Army Engineer Research and Development Center

Components of the Storm Surge Study Digital Elevation Model: 10m DEM created with the most updated topo/bathy datasets Tropical and Extratropical winter storms modeling using PBL & HBL wind models coupled with ADCIRC Surge modeling performed using ADCIRC 2-D Wave Modeling performed using WaveWatch III and SWAN Tidal Calibration and Storm Hindcast Production Runs Statistical analysis of surge levels using JPM and EST techniques

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

Storm Selection Tropical storms and winter storms to be modeled Historical tropical storms parameters are statistically analyzed to develop synthetic storm tracks Each storm is weighted by probability of occurrence from parameter distribution/Joint Probability Method Synthetic storms modeled could be in the order of Winter storms will be modeled

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

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

Storm Forcing Modeled Tracks VA/DE/NJ Central Pressure Difference Heading 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 Demonstrated validity with comparisons to historic data

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 Region III DEM 10-m Resolution 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

High Resolution Bathymetry and Topography Mesh triangulation through alignment with DEM features ADCIRC Modeling Mesh Project Site

High Resolution Bathymetry and Topography Mesh triangulation through alignment with DEM features Interpolation of DEM elevations to mesh Manual insertion of control points Elevations (m)

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

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 QA/QC of all Submittals

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

Transect Placement Shoreline in High and Low Population Density Areas

Field Reconnaissance

Erosion Analysis Dunes: Dune erosion based on the 540 sqft rule Dune retreat Dune removal Primary Frontal Dune (PFD) delineation Bluffs, Cliffs: Non-standard erosion based on historic data 100-year stillwater elevation Is it: > 540 square feet? or < 540 square feet? Primary Frontal Dune Reservoir Dune Crest

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

Added Detail with GIS

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

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 Summer Fall Anticipated Timeline Complete DEM Model validation Initiate production Complete production GIS site fully populated Hurricane Isabel September 2003

Preliminary coastal tasks expected to be performed prior to SWELs availability Bibliography, Data and Model Research Collect Base Data and create a DFIRM Database Prepare Modeling Methodology Summary Create transect layout in preparation of the field reconnaissance Field Reconnaissance Develop obstruction polygons using existing land use data or through aerial/field reconnaissance data Evaluate erosion methods

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

Questions?