FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

8 DETERMINING SITE-SPECIFIC LOADS Volume II
EXAMPLE 8.1. DESIGN STILLWATER FLOOD DEPTH CALCULATIONS (continued)
Find:
Illustration B. Primary frontal dune will be lost to erosion during a 100-year flood
because dune reservoir is less than 1,100 ft 2 (Section A of Illustration A)
The design stillwater flood depth (d s ) at the seaward row of piles for varying values of stillwater
elevation, presence of freeboard, and consideration of the effects of future conditions (e.g., sea-level
rise and long-term erosion).
The basis of the design flood for four scenarios are as follows:
1. 100-year stillwater elevation (NGVD). Future conditions not considered.
2. 100-year stillwater elevation (NGVD) plus freeboard. Future conditions not considered.
3. 100-year stillwater elevation (NGVD). Future conditions (sea-level rise and long-term erosion)
in 50 years considered.
4. 500-year wave crest elevation (NGVD). Future conditions not considered.
Note: Design stillwater flood depth (d s ) is determined using Equation A for scenarios in which a non-100year
frequency-based DFE is specified by the AHJ. Freeboard tied to the 100-year flood should not be used
to increase d s since load factors in ASCE 7 were developed for the 100-year nominal flood load.
8-12 COASTAL CONSTRUCTION MANUAL