Morganza to the gulf hurricane protection feasibility report march 2002
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Morganza to the Gulf Hurricane Protection Feasibility Report March 2002. Hydraulic Analysis. Interior Drainage Analysis. UNET (gradually varied unsteady flow 1D model that conserves energy & volume) Geometry - mixed, some new & some from earlier studies back to 1987, datum to NGVD

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Interior drainage analysis
Interior Drainage Analysis March 2002

  • UNET (gradually varied unsteady flow 1D model that conserves energy & volume)

  • Geometry - mixed, some new & some from earlier studies back to 1987, datum to NGVD

  • Datum errors as much as 1 foot in both topography and measured water levels.

  • Calibration - Hurricane Andrew (1992) and 1991 rainfall event


Adcirc modeling
ADCIRC Modeling March 2002

  • Grid developed from surveys, nautical charts & quadrangle maps

  • Verification – Carmen(1974), Juan (1985) & Andrew (1992)

  • 17 experienced storms from 1893 to 1992 used to generate data set

  • Storms experienced prior to ~1945 produced unacceptable results. Sparse storm data during this earlier period did not permit accurate computation of surge elevations


Frequency analysis
Frequency Analysis March 2002

  • EST (Emperical sampling technique) – not used to analyze ADCIRC results due to the lack of data during the 100 year storm analysis period, but used for UNET results with some smoothing

  • Plotting position formulation – used to generate exterior frequencies at gage locations and interpolated between.

  • HEC-FDA used to compute confidence bands based on estimated record length



Levee design
Levee Design March 2002

  • Windspeeds from GM – Larose GDM, 1972 (77mph = 100-yr frequency)

  • ACES used to determine Hs, T & Levee Height

  • Runup from Hs & T added to SWL determined levee height


Table 2.6.5. 100 Year Frequency Hurricane, Wave Characteristics And Design

Wave Runup And Design Elevations Of Protective Structures,

Highway 57 Alignment – Base Conditions


Morganza to the gulf hurricane protection restudy 2008
Morganza to the Gulf Characteristics And Design Hurricane Protection Restudy 2008


Interior drainage
Interior Drainage Characteristics And Design

  • HEC-RAS

  • Geometry – from ADCIRC grid

  • Grid composed of ~ 10-year old Lidar

  • Original datum adjusted to NAVD88(2004.65)

  • May 2008 - Corrections grid datum using latest survey data

  • Calibration - Hurricane Rita (2005) and a recent rainfall event


New adcirc modeling
‘New’ ADCIRC Modeling Characteristics And Design

  • Preliminary stages generated in LACPR study not used due to errors in grid datum and recent availability of new survey data

  • Restudy will use a sub-set, 54 hypothetical storms, specifically for Morganza region

  • Verification – Rita(2005)

  • Model - base & future, w & w/o levee alignments


Frequency analysis1
Frequency Analysis Characteristics And Design

  • JPM-OS (Joint probability-optimum sampling technique)

  • Products will be 50-, 100-, 500- & 1000-yr frequency stages

  • & Confidence bands


Levee design1
Levee Design Characteristics And Design

  • Waves – STWAVE (using ADCIRC grid) Hs & T plus confidence bands generated for required frequencies

  • Standard deviations (std) for SWL, Hs, & T

  • Runup & overtopping at 50% confidence from PCOverslag determines levee slope.

  • Design Height determined at overtopping limit of 0.1 cfs/linear foot at 90% confidence for base & future conditions


Structure design
Structure Design Characteristics And Design

  • Waves – STWAVE (using ADCIRC grid) Hs & T plus confidence bands generated for required frequencies

  • Standard deviations (std) for SWL, Hs, & T

  • Design Heights determined for vertical walls by overtopping limit of 0.1 cfs/linear foot at 90% confidence for future conditions


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