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
  • 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
  • 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
  • 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
  • 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
slide8

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

interior drainage
Interior Drainage
  • 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
  • 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
  • JPM-OS (Joint probability-optimum sampling technique)
  • Products will be 50-, 100-, 500- & 1000-yr frequency stages
  • & Confidence bands
levee design1
Levee 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
  • 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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