Modeling to Revise Coastal Inundation and Flooding Estimates in Georgia and Northeast Florida Association of State Flood Plain Managers Conference May.

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?