EM 1110-2-1100 (Part V)
31 Jul 2003
and summarizes knowledge on the interaction of armored shorelines and adjacent beaches. See also Engineer
Manual 1110-2-1614, "Design of Coastal Revetments, Seawalls, and Bulkheads."
(3) Beach stabilization. Headland and nearshore breakwaters, groins, sills and reefs, and wetlands all
moderate the coastal sediment transport processes to reduce the local erosion rate. These structures should
be considered where chronic erosion is a problem due to the diminished sediment supply. They are often
combined with beach nourishment to reduce downdrift impacts. Their purpose is to slow the loss of placed
sand, not to trap sand from the littoral system and create more problems elsewhere. In many locations, their
improper functional design, or construction without adding extra material, has produced adverse
environmental impacts by starving the supply of sand to downdrift beaches. Their proper design is one of
the great challenges of coastal engineering, and functional design aspects are found in Part V-3-3.
(4) Beach nourishment. Loose sediment material can be placed on the subaerial beach, as underwater
mounds, across the subaqueous profile, or as dunes to rebuild the dunes. The soft alternative solution for
shore protection is now the common alternative selected for a variety of reasons (constraints). Because of
its importance, a separate chapter, Part V-4 contains all the details for design.
(5) Adaptation and retreat. Elevating structures, flood proofing, zoning restrictions, storm warning and
evacuation planning are some of the types of coastal adaptation methods. Further details are in Part V-3-4-b.
Retreat is permanent evacuation or abandonment of coastal infrastructure, and for communities subject to
high erosion rates and flooding damages, this is always a possible alternative. Total costs and constraints of
this alternative must include the environmental impact on the new site to where "retreat" takes place. In
contrast to the engineering, decision-making process to determine the best alternative considering all the
design constraints for each site, some advocate retreat as the only solution. Further discussion is in section
Part V-3-4-c.
(6) Combinations and new technologies. In many locations, elevated structures combined with some
type of armoring or shoreline stabilization structure together with beach nourishment are employed for shore
protection. Nontraditional technologies (e.g., beach drains, geotextile bags, artificial breakwater structures,
wetlands, etc.) are also being investigated in field experiments. Part V-3-5 gives more details.
(7) Do nothing. Finally, the option to allow continued erosion and storm damage with the expected,
annual costs for this choice should be determined. The without project condition provides the basis for
measuring the effectiveness to reduce the expected damages of each proposed alternative. Further details for
estimating damage costs are in Part V-3-1-c. Part V-3-6 presents more general information on this option.
See also Part VI-2-1 for more details regarding various subtypes of the armoring, shoreline stabilization, and
beach nourishment alternatives. Each alternative must be considered under a wide variety of design
constraints.
c. Design constraints.
One good definition of engineering is "design under constraint." Engineering is creating and designing what
can be, but it is constrained by our understanding of nature, by economics (costs), by concerns of
environmental impact, by institutional, social, legal issues and possibly by aesthetics. Listed are the five
design constraint categories which are discussed further in the following paragraphs.
Shore Protection Projects
V-3-7
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