FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

Volume II DETERMINING SITE-SPECIFIC LOADS 8
8.5.3 Design Stillwater Flood Depth
In a general sense, flood depth can refer to two different depths
(see Figure 8-5):
Stillwater flood depth. The vertical distance between
the eroded ground elevation and the stillwater elevation
associated with the design flood. This depth is referred to
as the design stillwater flood depth (d s ).
COASTAL CONSTRUCTION MANUAL
NOTE
The design stillwater flood depth
(d s ) (including wave setup; see
Section 8.5.4) should be used
for calculating wave heights and
flood loads.
Design flood protection depth. The vertical distance between the eroded ground elevation and the
DFE. This depth is referred to as the design flood protection depth (d fp ) but is not used extensively in
this Manual. This Manual emphasizes the use of the DFE as the minimum elevation to which floodresistant
design and construction efforts should be directed.
Determining the maximum design stillwater flood depth over the life of a building is the most important
flood load calculation. Nearly every other coastal flood load parameter or calculation (e.g., hydrostatic load,
design flood velocity, hydrodynamic load, design wave height, DFE, debris impact load, local scour depth)
depends directly or indirectly on the design stillwater flood depth.
Figure 8-5.
Parameters that are
determined or affected by
flood depth
8-9