US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Modeling Nearshore Waves for Hurricane Katrina
Jane McKee SmithUS Army Engineer Research & Development Center
Coastal and Hydraulics Laboratory
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Outline• Introduction• Modeling Approach• Hurricane Katrina Simulations• Sensitivity Analysis• Summary and Conclusions
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Hurricane KatrinaCat 3 on 27 August 2005 to Cat 5 on 28 AugPeak: 280 km/hr, 902 mbLandfall Louisiana: 29 Aug, Cat 3, 205 km/h, 920mbLandfall Mississippi: Cat 3, 195 km/hrHurricane force winds 190 km from centerOffshore wave heights ~17 m
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
IPETInteragency Performance Evaluation Task ForceEvaluate performance of Louisiana levee
systemhttps://ipet.wes.army.mil/Review: ASCE and National Research
CouncilHydrodynamic modeling methodologyCharacterize waves and water levels along
entire periphery of the hurricane protection system
Winds, waves, and surge
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Modeling MethodologyWind/Pressure
Field Generation
Offshore Wave Modeling
Circulation Modeling
Nearshore Wave Modeling
Local-Scale Wave Modeling
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Wind and Atmospheric Pressure FieldsPrimary input to Wave and Storm Surge ModelingWind fields are blend of measurements and modeling• NOAA HRD H*Wind
snapshots • Blended to NCEP model
winds and data using IOKA wind analysis process (OWI)
Most anemometers close to the storm failed near the peak
Max wind speeds exceed 51 m/s
Mark Powell, HRD
Vince Cardone & Andy Cox, OWI
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Offshore Wave Model -- WAM
Max Computed Wave Height – 16 m
Basin – Regional WAM c4.5
Resolution 0.1 deg, 0.0083 deg
Wave-storm surge interaction neglected at basin & region level
WAM-WAVEWATCH III comparisons
WAM Basin
Max Wave Height Map, ft
WAM Regional
Bob Jensen, CHL
Barbara Tracy, CHL
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Buoy 42007Buoy 42040
Wave Height
Peak Period
Mean Period
Wave Dir
Wind Speed
Wind Dir
Max 16.8
Max 15 sec
Max 13 sec Max 12 sec
Max 15 sec
Max 7 m
Max 33.4 m/sMax 30.9 m/s
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
ADCIRC – Surge Model1165122 elements598240 nodes
Joannes Westerink, Notre Dame
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Katrina STWAVE Grids
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
South Louisiana Wave Heights
Mississippi River Delta
Metro New Orleans Mississippi River
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
South Louisiana Wave Periods
Mississippi River Delta
Metro New Orleans Mississippi River
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Southeast Louisiana Wave Heights
Chandeleur Islands
Mississippi River Delta
Lake Borgne
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Southeast Louisiana Wave Periods
Chandeleur Islands
Mississippi River Delta
Lake Borgne
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Mississippi-Alabama Wave Heights
Biloxi, MS Mobile, AL
Mobile Bay
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Mississippi-Alabama Wave Periods
Biloxi, MS Mobile, AL
Mobile Bay
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Lake Pontchartrain
Metro New Orleans
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Lake Pontchartrain Wave Heights
Metro New Orleans
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Lake Pontchartrain Wave Periods
Metro New Orleans
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Lake Pontchartraing
0
0.5
1
1.5
2
2.5
3
3.5
29.00 29.10 29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90 30.00
Date (August 2005, UTC)
Hmo
(m)
Hm0 Meas 22Hm0 Meas 23Hmo Meas 22 (24 DOF)Hmo Meas 23 (24 DOF)STWAVE
0
1
2
3
4
5
6
7
8
29.00 29.10 29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90 30.00
Date (August 2005, UTC)
Peak
Wav
e Pe
riod
(sec
)
Tp Meas 22 (24 DOF)Tp Meas 23 (24 DOF)Tp STWAVE
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Sensitivity Analysis• Wind Input
+/- 5% wind speeds• Bathymetry
degraded Chandeleurs Islands• Bottom Roughness
pre- and post-Katrina roughness• Time Dependence
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Wind Sensitivity Wave Height Differences: +5% – Base
Result: ± 0.3 m near the shoreline
± 0.3 to 1.0 m offshore
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Bathymetry Sensitivity Wave Height Differences: Degraded – Base
Result: Maximum Difference 1.8 m
near zero difference at the shoreline
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Roughness Sensitivity:Pre-Katrina – Post-Katrina Roughness
Chandeleur Islands
Mississippi River Delta
Lake BorgneResult: 0.3-0.5 m decreased surge with decreased roughness
0.2 m increase in surge in limited areas
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Sensitivity: Time DependenceTime-Dependent v. Steady-State SWAN
0
0.5
1
1.5
2
2.5
3
29.00 29.10 29.20 29.30 29.40 29.50 29.60 29.70 29.80 29.90 30.00
Date (August 2005, UTC)
Hm
o (m
)
Gauge 22 (24 DOF)Gauge 23 (24 DOF)STWAVESteady-State SWANTime-Dependent SWAN
Time step 1 min
Steady 99% accuracy (15 iterations)
US Army Corpsof Engineers Coastal and Hydraulics Laboratory - ERDC
Summary• STWAVE Applied for Hurricane Katrina
• High resolution, half- and full-plane mode• Interactions with surge critical• Results used to evaluate design/response
• Results• Katrina wave heights near or exceeded design• Periods in many areas 2-3 times design values• Wave-surge-wetland interaction not simple “rule of thumb”• SHALLOW-WATER MEASUREMENTS NEEDED!
• Continuing Work• More validation (Katrina, Rita, Camille, Ivan, Betsy, Andrew)• Design studies for Mississippi and Louisiana coasts• FEMA flood mapping
