Coastal Construction Manual - National Ready Mixed Concrete ...

3 IDENTIFYING HAZARDS
Figure 3‐54.
Example DFIRM for a coastal area that shows the LiMWA
SOURCE: FEMA 2008c
A coastal FIS is completed with FEMA-specified techniques and procedures (see FEMA 2007) to determine
mean water levels (stillwater elevation plus wave setup) and wave elevations along transects drawn perpendicular
to the shoreline (see Figure 3-53). The determination of the 100-year mean water elevation (and elevations
associated with other return intervals) is usually accomplished through the statistical analysis of historical
tide and water level data, and/or by the use of numerical storm surge and wave models. Wave heights and
elevations on land are computed from mean water level and topographic data with established procedures
and models that account for wave dissipation by obstructions (e.g., sand dunes, buildings, vegetation) and
wave regeneration across overland fetches.
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