EM 1110-2-1100 (Part V)
31 Jul 2003
desired level of protection to the seaward most structures. If this is the case, other means for achieving the
desired level of storm protection in certain local areas, such as more frequent nourishment, use of a feeder
beach, a filled groin compartment, or a revetment or seawall, should be considered.
(g) There are probably other less well-understood causes for the development of hot spots. A geologic
control such as remnant morphologic feature (relic inlet) with a different sediment composition may cause
differential erosion along the project reach. Longshore variation in the sediment characteristics of the borrow
material may produce a differential loss rate within sections of the project. However at present, there are no
reliable methods for anticipating hot spots caused by these other factors.
h. Fill transitions.
(1) Selection of a method for terminating a beach nourishment project depends on several factors. One
important consideration is what lies immediately beyond the project limits. For example, is there an open
straight beach or an inlet? On open stretches of coast, transition to the adjacent beach can be accomplished
using a fill transition section, which was briefly introduced in the previous section, or using hard structures,
such as groins, navigation structures, or breakwaters. Structures placed at the boundaries of a project are
called terminal structures. If the project is constructed near an inlet, structures may be desirable to minimize
movement of fill material into navigation channels. Hard structures will allow an abrupt termination of the
beach-fill section. However, these structures can be costly, and can interfere with the natural longshore
transport of sediment along the shoreline. If not designed properly, this interference could result in adverse
effects along the unrestored beach and subsequent objections by adjacent-beach property owners.
(2) Another key factor is the purpose for building the project. If the project is built to provide storm
protection, what is the reach of shoreline to be protected and what is the desired level of protection within
the reach? The desire to maintain a specific design beach width may dictate the design of the transition
section. In practice, if a uniform design width is desired for the entire project reach, it will be extremely
difficult to maintain that width near the lateral ends of the project, unless a terminal structure is used or the
design fill is extended beyond the limits of the design reach. If sand is to be placed outside the design reach,
other issues become important. Can the fill provide benefits to the adjacent property, and how will those
benefits be factored into the economic justification of design (if at all)? It may be more practical to consider
the nourishment project in three sections, one interior section where a desired level of protection will be
maintained, and two outer sections of the project where a lesser degree of protection will exist (i.e., the
transition sections). In the transition sections, the level of protection will diminish with distance from the
main project reach.
(3) If the project is built primarily for recreational purposes, the design goal may be to maximize
retention of fill volume within the limits of the project reach. This design objective may dictate whether or
not fill transitions are used at all, and if so, how they are designed.
(4) Although sometimes approached as an afterthought in project design, beach-fill termination deserves
careful consideration. This is particularly true in terms of its relation to the economics of the project and the
level of storm protection that is sought/claimed near the limits of the project. This section discusses use of
fill transitions at the ends of a nourishment project. The next section, Part V-4-1-i, discusses use of structures
in fill stabilization.
(5) The intent of fill transitions is to minimize the effect of end losses on project integrity. End losses
from the main project reach can be reduced by extending the design section past the limits of the reach where
protection is desired, or by smoothly tapering the project into the adjacent beaches (i.e., gradually reducing
project width from the design width to zero). Tapering the fill ends will decrease the perturbation effects of
V-4-66
Beach Fill Design
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