stwave

Report
The Effects of Starting Wave
Conditions on Coastal Flood
Hazards:
A Sensitivity Analysis for the Texas Coast
Katrina Myers, PE, CFM
Guillermo Simón, PE, CFM
Outline
Background
WHAFIS Setup
Starting Wave
Conditions
Findings
Past FEMA Projects
Texas Coastal Projects
Subcontractor to
Halff & Associates
• Aransas County
• Calhoun County
• Jackson County
• Matagorda County
• Refugio County
• Victoria County
Prime Contractor
• Galveston County
Galveston County
WHAFIS modeling
Coastal mapping
FIS and DFIRM
Welcome to Galveston
Welcome to Galveston
Development
Coastal Structures
Bays
Long History of Storms…
Ike
2008
1915
1900
Carla
1961
Alicia
1983
Long History of Storms…
WHAFIS Overview
Transects
USACE Storm Surge
Land Cover
Topography/Bathymetry
Starting wave conditions
Options
•Fetch
•STWAVE
•Hindcast Data
Starting Wave Conditions: Fetch
Starting Wave Conditions: STWAVE
− ADCIRC
− WAM
− STWAVE
Starting Wave Conditions: STWAVE
2D wave model,
uses output from
model surface as
WHAFIS starting
wave height and
period
.
STWAVE Tp
Starting Wave Conditions: Hindcast Data
Hourly wave data
from WIS stations
Starting Wave Conditions: Hindcast Data
Starting Wave Conditions: Hindcast Data
Starting Wave Conditions: Hindcast Data
Relationship Between Tp and Hmo
Overview Map
Coastal Analyst
Taylor Engineering-developed
GIS tool for WHAFIS modeling
and mapping
Transect 18
Gulf T18, Starting Conditions
Fetch
Hindcast Data
STWAVE
Tp (sec)
6.44
12.21
11.45
Hc (ft)
9.48
10.45
10.45
Ground
0 ft NAVD
Stillwater
Depth Limited Wave
Height
13.40 ft NAVD
10.45 ft
Gulf T18, Buildings
Wave Crest Elevation
Gulf T18, Open Water
Wave
WaveCrest
CrestElevation
Elevation
Gulf T18, Marsh
Wave
WaveCrest
CrestElevation
Elevation
Transect 18
Bay T18, Bay Shoreline
Fetch
Tp (sec)
6.92
Hc (ft)
8.89
Bay Fetch
3.87
7.34
Hindcast Data
12.21
11.45
9.26
9.22
5.3
8.45
Stillwater
Depth Limited Wave
Height
14.05 ft NAVD
Fetch Length
3.16 miles
STWAVE
Bay STWAVE
10.96 ft
Bay T18, Bay Shoreline
Wave Crest Elevation
Conclusions
Higher Wave Period from STWAVE and Hindcast Data
compared to fetch
No difference after transect crosses high ground/
above surge areas
Very little difference on wave crest elevation for
areas where wave is dampened by buildings or trees
Conclusions
Less than 0.5ft difference in areas where wave
is regenerating in marsh and open water
Larger differences between transects
originating in the bay compared to the Gulf
Potential impact on wave runup
Thank you

similar documents