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Results of Cameron Parish DFIRM appeal

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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

slide32
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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