Modeling to Revise Coastal Inundation and Flooding Estimates in Georgia and Northeast Florida Association of State Flood Plain Managers Conference May 22, 2012 Christopher Bender, PhD, PE, D.CE — Taylor Engineering Ashley Naimaster, EI— Taylor Engineering William Miller, PhD, PE— Taylor Engineering Tucker Mahoney, PE — FEMA Region IV

Overview Project background About SWAN+ADCIRC Model mesh development Validation results Production runs Conclusions

Project Background FEMA multiyear coastal engineering analysis and mapping effort 100-year storm surge elevations Model winds, hydrodynamics, offshore and nearshore waves Georgia and northeast Florida Update DFIRMs

Study Location Entire coast of Georgia and Florida counties north of Brevard Extend inland to 40 ft contour

Data and Methods Improved Data o LiDAR data o Wind fields (simulate real events and synthetic events) o GIS data sets – land use, coastal features Improved Methods o Better mesh/resolution o Better hydrodynamics - ADCIRC o Include wave setup – dynamically linked o Faster, more powerful, computers

Project Background

SWAN+ADCIRC Water levels + currents + waves Parallelized code Forcing Wind speed, barometric pressure Tides Riverine flow Output Water surface elevation Velocity Wave height, peak period, mean period, direction Tightly-coupled

Input Data Recent LiDAR data captured for the State with FEMA funds Aerial photography Land use with national, regional, and local scale Field investigations

Model Mesh Development Surface-water Modeling System Need to digitize: Obstructions to flow Flow paths Mesh quality

Model Mesh Development Elevation (ft-NAVD)

Model Mesh Development 2.9 million nodes Minimum nodal spacing = 50 m

Spatially Variable Nodal Attributes Manning’s n Wind reduction roughness length

Mesh Resolution Average nodal spacing (ft)

Bathymetric Mesh University of Central Florida CHAMPS Lab

Hurricane Dora September, 1964 Landfall near St. Augustine, FL

Hurricane Dora

H s at Maximum Water Level (ft) Setup at Maximum Water Level (ft)

Hurricane David September, 1979 Initial landfall near West Palm Beach, FL. Exited near New Smyrna Beach, FL, and made final landfall near Savannah, GA Results presented do not include waves

Hurricane David

Production Runs ~ 400 storms Liveoak HPCC – Worldwinds, Inc. 528 cores Handles post-processing plots

Conclusions Preliminary results appear reasonable Next steps: o Continued model validation  Tidal validation  Historical storm validation o Wave data comparison o Sensitivity testing with ADCIRC and SWAN parameters

Questions?

Hurricane Dora

May port