EM 1110-2-1100 (Part V)
31 Jul 2003
EXAMPLE PROBLEM V-4-4
FIND:
Sectional fill volume that must be placed before any dry beach width is added after equilibrium.
Disregard any volume necessary to makeup for a preproject sediment deficit in the beach profile.
GIVEN:
Berm height of 2.5 m and depth of closure of 6 m. Native sand median grain size of 0.26 mm
and fill sand median grain size of 0.19 mm.
SOLUTION:
Values of the A parameter for native and fill sand are read from Table III-3-3.
AN = 0.117 m1/3, AF = 0.097 m1/3
Profile is nonintersecting because AF <AN, therefore Equation V-4-8 is applicable.
Equation V-4-8 gives
5/2
3
6
' 361 m 3/m
V' @
@ 0.117&0.097
5
0.097
This illustrates that when filling with sand finer than the native beach material, a significant amount of
sand must be placed before any dry beach width is produced after equilibrium. Note that the sectional
fill volume is 140 percent of the sectional fill volume computed in Example V-4-3, and the present
example will produce no additional dry beach width whereas 30 m of additional dry beach width is
obtained in Example V-4-3.
added. The overfill method can compliment calculations made using the other methods, but it is not
recommended for final fill volume computations.
g. Evaluating project longevity
The longevity of a beach nourishment project is primarily determined by the degree to which the placed sand
volume addresses any preproject profile volume deficit, and the rate at which fill material is transported out
of the project domain in the alongshore direction, i.e, lateral spreading losses. Wave-driven longshore sand
transport processes are the major cause of lateral spreading. Projects tend to be built in erosional areas where
waves act to move sand out of the project domain, in a long-term, net sense. In addition to the wave climate
and its interaction with the local morphology, there is another important aspect of lateral spreading. The
project itself creates a perturbation in shoreline and beach orientation, particularly where the fill transitions
into the adjacent beaches. At these transitions, local wave transformation patterns and consequently the
longshore sand transport regime are altered, which can lead to high rates of fill loss from the ends of the
project (often called end losses). Coastal structures that exist within the project domain, or are built as part
of the project, also can impede alongshore sand movement and influence the rate of sand loss. Grain size
characteristics of the fill material may be a factor in determining beach-fill longevity. Part III discusses
dependency of longshore sand transport on grain size. However, in practice, the role of grain size is not
usually considered in evaluating lateral spreading losses.
V-4-46
Beach Fill Design
Previous Page
