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Results of Cameron Parish DFIRM appeal PowerPoint Presentation
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Results of Cameron Parish DFIRM appeal
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  1. 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)

  2. 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

  3. ABFE

  4. DFIRM

  5. 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

  6. CAMERON PARISH AREA

  7. 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

  8. Adcirc / lidar comparison:LITTLE CHENIER MAX ELEVATION: 2.22 FEET Rev 12-15-2008

  9. Adcirc / lidar comparison:LITTLE CHENIER MAX ELEVATION: +10 FEET Rev 12-15-2008

  10. 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

  11. LIDAR COMPARISON LARGE INTERPOLATIONS OMIT MAJOR TERRAIN FEATURES Rev 12-15-2008

  12. LIDAR / SURVEY comparison • THE FOLLOWING SLIDES ILLUSTRATE THE DISCREPANCIES BETWEEN LIDAR TOPOGRAPHIC DATA AND LGH & ASSCS GPS SURVEYED TOPOGRAPHIC DATA Rev 12-15-2008

  13. LIDAR / SURVEY comparison Rev 12-15-2008

  14. MODEL ERRORS Rev 12-15-2008

  15. 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

  16. 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

  17. 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

  18. STARTING POINT SHIFT: AREA BETWEEN HOLLY BEACH AND CAMERON COMMAND STATION DISTANCE FROM BEGINNING ELEVATION VEG TYPE Rev 12-15-2008

  19. STARTING POINT SHIFT: SOUTHEASTERN MOST TRANSECT Rev 12-15-2008

  20. 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

  21. OF vs VH COMMAND LINE Rev 12-15-2008

  22. 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

  23. OF vs IF COMMAND LINE SHOULD BE MODELED AS IF COMMAND LINE RATHER THAN OF Rev 12-15-2008

  24. 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

  25. Rev 12-15-2008

  26. 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

  27. VEG MAPS: WEST CAMERON PARISH HACKBERRY CALCASIEU LAKE CREOLE CAMERON HOLLY BEACH JOHNSONBAYOU OAKGROVE GULF OF MEXICO Rev 12-15-2008

  28. 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

  29. CORRECTED WHAFIS SIMULATIONS A ZONES ACHIEVED WITH PROPER STARTING POINT, ELEVATIONS, COMMAND LINES, AND DEFAULT VALUE FOR Cd Rev 12-15-2008

  30. A ZONES: CAMERON A ZONES INCREASE DRAMATICALLY AS Cd INCREASES Rev 12-15-2008

  31. 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

  32. ABFE Rev 12-15-2008

  33. LGH Revised Rev 12-15-2008

  34. DFIRM

  35. LGH Revised Rev 12-15-2008