FIGURE 5.3 Current FEMA coastal mapping procedures used in Mississippi and Louisiana. In these studies, two-dimensional surge (ADCIRC) and wave (SWAN for Mississippi and STeady State spectral wave [STWAVE] for Louisiana) models are used to calculate the 1 percent annual chance stillwater elevation, and CHAMP/WHAFIS is used to calculate overland wave crest and post-storm topography. The 1 percent annual chance SWEL and the wave crest are then combined to calculate the BFE. NOTE: FIRM = Flood Insurance Rate Map.

FIGURE 5.3 Current FEMA coastal mapping procedures used in Mississippi and Louisiana. In these studies, two-dimensional surge (ADCIRC) and wave (SWAN for Mississippi and STeady State spectral wave [STWAVE] for Louisiana) models are used to calculate the 1 percent annual chance stillwater elevation, and CHAMP/WHAFIS is used to calculate overland wave crest and post-storm topography. The 1 percent annual chance SWEL and the wave crest are then combined to calculate the BFE. NOTE: FIRM = Flood Insurance Rate Map.

TABLE 5.1 Elements of FEMA’s Current Coastal Flood Mapping Process

Empirical and Probabilistic Input Data

Coupled Surge and Wave Models for SWEL Calculation

Wave Crest and BFE Calculation

  • Hurricane data

  • Probabilistic hurricane wind model data

  • Hurricane ensemble and return period data

  • Bathymetric data

  • Pre- and post-storm topographic data

  • 2-D storm surge model

  • 2-D wave model

  • CHAMP/WHAFIS erosion and wave calculations along one-dimensional (1-D) transects

  • Post-storm topographic data to verify CHAMP/WHAFIS results



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