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Lonnie G. Harper & Associates, Inc. Results of Cameron Parish DFIRM appeal. Lonnie G. Harper, PE & PLS (LGH) David Minton, PE (LGH) Dr. Joseph Suhayda (Coastal Oceanographic Consultant) Dr. Roy Dokka (LSU C4G) Dr. Eddie Lyons (McNeese State University). Key Parish concerns.

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Lonnie g harper associates inc

Lonnie G. Harper & Associates, Inc.

Results of Cameron Parish DFIRM appeal

Lonnie G. Harper, PE & PLS (LGH)

David Minton, PE (LGH)

Dr. Joseph Suhayda (Coastal Oceanographic Consultant)

Dr. Roy Dokka (LSU C4G)

Dr. Eddie Lyons (McNeese State University)


Key parish concerns
Key Parish concerns

  • THE PRELIMINARY DFIRMs RESULT IN A SIGNIFICANT CONVERSION OF A ZONES TO V ZONES IN CAMERON PARISH

  • BUILDING WITHIN V ZONES RESULTS IN INCREASED CONSTRUCTION COSTS

  • FEDERAL ASSISTANCE IS UNAVAILABLE IN V ZONES




Technical issues storm surge
TECHNICAL ISSUES: Storm Surge

  • CALIBRATION ERRORS ARE PRESENT ASSOCIATED WITH THE HINDCAST FOR HURRICANE RITA: ERRORS IN PREDICTED HIGH-WATER MARKS (HWM) COMPARED TO MEASURED HWM AS GREAT AS+/- 4.5 FEET

  • AN EXAMINATION OF THE PRELIMINARY ADCIRC GRID HAS REVEALED MAJOR CHENIER RIDGES, LEVEES, MANMADE FEATURES, AND OTHER TOPOGRAPHIC DATA WERE OMITTED FROM THE MODEL



Topographic data
TOPOGRAPHIC DATA

  • LGH COMPLETED A REVIEW OF MUCH OF THE TOPOGRAPHIC DATA USED FOR FIS

  • FIELD SURVEY DATA HAS BEEN GATHERED FOR COMPARISON TO ADCIRC AND LIDAR

    • ADCIRC VS. LIDAR

    • WHAFIS VS. LIDAR

    • LIDAR VS. SURVEY ELEVATIONS


Adcirc lidar comparison little chenier
Adcirc / lidar comparison:LITTLE CHENIER

MAX ELEVATION:

2.22 FEET

Rev 12-15-2008


Adcirc lidar comparison little chenier1
Adcirc / lidar comparison:LITTLE CHENIER

MAX ELEVATION:

+10 FEET

Rev 12-15-2008


Lidar concerns
LIDAR CONCERNS

  • LIDAR NAVD88 (2004.65) WAS REPORTEDLY USED AS THE VERTICAL DATUM

  • THE SPARSENESS OF FEMA’S TOPOGRAPHIC DATA USED IN THEIR WHAFIS MODEL OMITS MAJOR TERRAIN FEATURES

  • FOLLOWING SLIDES ILLUSTRATE DIFFERENCES BETWEEN ELEVATIONS FROM FEMA’S WHAFIS MODEL AND ELEVATIONS EXTRACTED FROM LIDAR NAVD88 (2004.65)

Rev 12-15-2008


Lidar comparison
LIDAR COMPARISON

LARGE INTERPOLATIONS

OMIT MAJOR TERRAIN FEATURES

Rev 12-15-2008


Lidar survey comparison
LIDAR / SURVEY comparison

  • THE FOLLOWING SLIDES ILLUSTRATE THE DISCREPANCIES BETWEEN LIDAR TOPOGRAPHIC DATA AND LGH & ASSCS GPS SURVEYED TOPOGRAPHIC DATA

Rev 12-15-2008



Model errors
MODEL ERRORS

Rev 12-15-2008


Whafis errors
WHAFIS ERRORS

  • STARTING POINT TYPICALLY BEGINS 500 FEET IN GULF OF MEXICO

  • DUNE (DU) COMMAND LINE USED TO MODEL STRUCTURES SUCH AS LEVEES OR SEAWALLS OMITTED FROM THE WHAFIS MODEL

  • WHAFIS TERRAIN DATA DOES NOT REFLECT ACTUAL CONDITIONS

    • OVERWATER FETCH (OF) VS. INLAND FETCH (IF) AND VEGETATION HEADER (VH)

Rev 12-15-2008


Whafis errors1
WHAFIS ERRORS

  • A ZONE AREAS AS DEFINED BY WHAFIS ARE OMITTED FROM DFIRMs

  • IMPROPER DEFINITION OF DRAG COEFFICIENT FOR VEGETATION HEADER COMMAND LINES

Rev 12-15-2008


Starting point shift
STARTING POINT SHIFT

  • EVERY WHAFIS TRANSECT (104) HAS BEEN SHIFTED SOUTH RESULTING IN THE STARTING POINT OF EACH TRANSECT BEING OVER THE OPEN WATER OF THE GULF OF MEXICO

  • THIS HAS RESULTED IN STATIONS, WITH COMMAND LINES MODELING VEGETATION (VH OR VE), BEING LOCATED OVER OPEN WATER

Rev 12-15-2008


Starting point shift area between holly beach and cameron
STARTING POINT SHIFT: AREA BETWEEN HOLLY BEACH AND CAMERON

COMMAND

STATION DISTANCE

FROM BEGINNING

ELEVATION

VEG TYPE

Rev 12-15-2008



Of vs vh command line
OF vsvh command line

  • THERE ARE MANY INSTANCES OF OVERWATER FETCH (OF) COMMAND LINES BEING USED WHERE VEGETATION HEADER (VH) COMMAND LINE SHOULD BE USED. THIS, IN EFFECT, CAUSES A LAKE TO MODELED IN REGIONS WHERE EMERGENT LAND EXISTS

  • ONE EXAMPLE IS THE SOUTHERN END OF TRANSECT 17, LOCATED IN THE JOHNSON BAYOU AREA

Rev 12-15-2008


Of vs vh command line1
OF vs VH COMMAND LINE

Rev 12-15-2008


Of vs if command line
OF vs IF COMMAND LINE

  • OF (OVERWATER FETCH) COMMAND LINE IS USED FOR WATER WITH DEPTHS GREATER THAN 10 FEET, SUCH AS LAKES OR BAYS

  • IF (INLAND FETCH) COMMAND LINE IS FOR SHELTERED WATER WITH A DEPTH OF LESS THAN 10 FEET

Rev 12-15-2008


Of vs if command line1
OF vs IF COMMAND LINE

SHOULD BE MODELED

AS IF COMMAND LINE

RATHER THAN OF

Rev 12-15-2008


Wave model validation
Wave Model Validation

  • LGH INSTALLED SENSORS THROUGHOUT CAMERON PARISH FOR HURRICANE IKE

    • 7 UNITS AT 0.5 SECOND INTERVALS

    • 4 UNITS AT 2 SECOND INTERVALS

  • LGH CREATED A WAVE HEIGHT TO WATER DEPTH RATIO FROM ACTUAL FIELD DATA FROM HURRICANE IKE

Rev 12-15-2008



Vegetation maps
VEGETATION MAPS

  • ONLY ONE TYPE OF VEGETATION (SPARTINA PATENS) WAS USED IN FEMA’S WHAFIS MODEL

  • CAMERON PARISH CONTAINS AT LEAST FIVE (5) DIFFERENT TYPES OF TERRAIN:

    • FRESHWATER MARSH

    • INTERMEDIATE MARSH

    • BRACKISH MARSH

    • SALTWATER MARSH

    • OTHER (EMERGENT TERRAIN USUALLY FOUND ON CHENIER RIDGES)

Rev 12-15-2008


Veg maps west cameron parish
VEG MAPS: WEST CAMERON PARISH

HACKBERRY

CALCASIEU

LAKE

CREOLE

CAMERON

HOLLY BEACH

JOHNSONBAYOU

OAKGROVE

GULF OF MEXICO

Rev 12-15-2008


Corrected whafis simulations
CORRECTED WHAFIS SIMULATIONS

  • ALL TRANSECTS WERE MODIFIED AND RECOMPUTED BY LGH BASED ON THE FOLLOWING INPUT MODIFICATIONS:

    • STARTING POINT PLACED IN PROPER POSITION

    • PROPER COMMAND LINES INSERTED IN INPUT FILES

    • CORRECTED ELEVATIONS

    • CORRECTED VEGETATION PROPERTIES

Rev 12-15-2008


Corrected whafis simulations1
CORRECTED WHAFIS SIMULATIONS

A ZONES ACHIEVED WITH

PROPER STARTING POINT,

ELEVATIONS, COMMAND LINES,

AND DEFAULT VALUE FOR Cd

Rev 12-15-2008


A zones cameron
A ZONES: CAMERON

A ZONES INCREASE

DRAMATICALLY AS

Cd INCREASES

Rev 12-15-2008


Summary
SUMMARY

  • LOW RESOLUTION OF TOPOGRAPHIC DATA IN ALL MODELS

  • POOR CALIBRATION OF SURGE MODEL

  • IMPROPER APPLICATION OF INPUT DATA

  • INCONSISTENT ELEVATION DATA BETWEEN MODELS

  • OMISSION OF INPUT DATA

  • USE OF REGIONAL SURGE MODEL FOR A SMALL GEOGRAPHIC AREA WITH UNUSUAL TOPOGRAPHIC FEATURES MAY YIELD QUESTIONABLE SWEL RESULTS

Rev 12-15-2008


ABFE

Rev 12-15-2008


Lgh revised
LGH Revised

Rev 12-15-2008



Lgh revised1
LGH Revised

Rev 12-15-2008


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