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 EngineeringAshley Naimaster, EI— Taylor Engineering

William Miller, PhD, PE— Taylor EngineeringTucker 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 Datao LiDAR datao Wind fields (simulate real events and synthetic events)o GIS data sets – land use, coastal features

• Improved Methodso Better mesh/resolutiono Better hydrodynamics - ADCIRCo Include wave setup – dynamically linkedo Faster, more powerful, computers

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

Hurricane Dora

Hs 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

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 comparisono Sensitivity testing with ADCIRC and SWAN parameters

Questions?