EM 1110-2-1100 (Part V)
31 Jul 2003
tide conditions and has similar grain size characteristics, can be used to estimate the healthy beach profile
shape for reaches where in situ profiles might be misleading. Figure V-4-15 shows an eroded profile in front
of an exposed seawall. Translating the existing profile would incorrectly estimate the shape of the nourished
beach and would result in an underestimate of the volume required to obtain the design beach width in front
of the seawall. In Figure V-4-15, the design profile is determined by translating the natural (healthy) profile
shape seaward to obtain the design berm width in front of the seawall. Grain-size differences between the
native beach and the fill material also must be considered in defining the design profile shape. If the median
grain size of the fill is the same as that of the native beach, the design profile shape should be obtained by
translating an average profile shape that represents locally healthy (sediment-rich) beach conditions. For
example, given the same composite median grain sizes, the design profile for a beach with 30 m of added
berm width is determined by translating the existing profile 30 m seaward between the elevation of the berm
crest and the depth of closure, as shown in Figure V-4-14. When applying the profile translation method, the
existing beach shape should be determined based on an average of multiple surveys to account for seasonal
and/or alongshore variability in profile shape and to avoid including anomalous profile features in the design
profile shape.
(a) When fill material is finer or coarser than the native sediment, the design beach profile shape should
be estimated based on equilibrium profile concepts (see Part III-3-3-c for details on equilibrium beach
profiles). According to equilibrium profile theory, coarser sand will produce a steeper design profile whereas
finer sand will produce a profile with a gentler slope as illustrated in Figure V-4-16. Dean (1991) provides
additional discussion of equilibrium beach profile concepts and their application. To estimate the design
profile shape using equilibrium profile concepts, the average profile shape that represents locally healthy
(sediment-rich) beach conditions should first be translated seaward a distance equal to the added berm width
(see Figure V-4-14 and Figure V-4-15). To account for the difference in profile shape due to different
composite sand sizes, the profile is translated an additional distance as a function of depth between the still-
water level and depth of closure, based on differences in the theoretical equilibrium profile shapes as shown
in Figure V-4-17. The added distance of translation Wadd as a function of depth y is given by
3/2
3/2
1
1
3/2
Wadd y ' y
(V-4-5)
&
AF
AN
where AN is the A parameter for native sand and AF is the A parameter for fill sand (see Table III-3-3 for
values of the A parameter for different sand sizes). In Equation V-4-5, when the fill material is finer than
the native sand, Wadd is positive, which produces a design profile that is gentler in slope than the native
profile. Conversely, for fill that is coarser than the native beach, Wadd is negative which produces a steeper
design profile. If the representative sediment-rich beach profile includes a bar, some smoothing in the bar
region may be necessary. The BMAP software provides automated methods for estimating the design profile
shape for different native and fill sand sizes based on Equation V-4-5, and for the same sand sizes using the
uniform profile translation technique.
(5) Optimization of design profile. Optimization of the design profile involves selecting a range of
design alternatives with different dune and berm dimensions, and evaluating the design alternatives together
with the existing condition to determine the alternative that provides maximum net economic benefits. Storm-
induced beach erosion modeling is the primary engineering analysis performed as part of the optimization
process. Model simulations of profile response to a suite of historical or characteristic storms are performed
for each alternative to assess erosion, flooding, and wave attack damages to shorefront property and
infrastructure.
Beach Fill Design
V-4-35
Previous Page
