EM 1110-2-1100 (Part V)
31 Jul 2003
(a) Beach stabilization structures and beach nourishment. Groins and detached breakwaters combined
with beach fills are discussed in Part V-3-3e. The combination mitigates downdrift impacts and/or increases
the fill life of the renourished beach. Together, their life-cycle costs and environmental impact may be less
than if selectively implemented. Construction of the beach stabilization structures without fill is likely to
damage adjacent beaches.
(b) Seawalls, revetments, and beach nourishment. The original design of the new seawall for hurricane
protection at Virginia Beach was to be a curved, concrete-type structure as at Galveston, Texas (Figure V-3-
5). To accommodate a lowered seawall crest for aesthetic reasons (see Part V-3-1-c-(5)and Figure V-3-6)
a wide beach nourishment project was added to the design to reduce flooding and wave damage (USAED,
Norfolk, 1994). Together with improved interior drainage and pumping equipment, this combined design
provides the same hurricane flooding and wave damage protection as the original seawall design.
(c) Beach nourishment and rebuilt dune with buried seawall/revetment. The soft alternative (beach and
dune with buried rock seawall/revetment) was determined to be both environmental and economically
advantageous when compared against an armored revetment for storm protection against the 1 percent change
storm event at Dam Neck, Virginia, on the Atlantic Ocean (Basco 1998). The final design cross section is
shown in Figure V-3-36a and includes a buried rock seawall/revetment beneath the dune. In the event of a
major storm causing severe dune erosion, the buried seawall will prevent storm damage if a second major
storm occurs in the same season. Figure V-3-36b shows a photograph of dune construction with the buried,
rock seawall (Basco 2000a). A similar approach was incorporated at Ocean City, Maryland, where a steel,
sheet-pile bulkhead was incorporated as a buried backup feature in the design.
At many locations, elevated structures combined with some type of armoring or shoreline stabilization
together with beach nourishment are employed in combination for coastal hazard mitigation. Presently, 32
of 35 coastal states and territories have some type of setback requirements for new construction and existing
structures found uninhabitable after a storm (Heinz Center 2000). These nonstructural, adaptive measures
and structural alternatives are often combined to address the wide range of coastal problems previously cited.
An example is the barrier island of Grand Isle, Louisiana, where beach nourishment, rebuilt dunes, a groin
field and nearshore breakwaters are used for a community where the first floor of most residences are
constructed above the 1 percent chance flood level (with waves) and the public lands on the rapidly eroding
east end are restricted from any development (Pope 1997).
b. New technologies.
Many nontraditional ways to armor, stabilize, or restore the beach including the use of patented, precast
concrete units, geotextile-filled bags, and beach dewatering systems have been tried in the field. Their
success depends on their stability during storm events and durability over the economic, design life. Their
initial cost and cost for removal if environmental impacts warrant can be less than traditional methods, at
some sites. These new technologies often involve nontraditional materials or shapes but are employed in a
traditional manner, e.g., nearshore breakwaters. See Pope (1997) for more details.
Shore Protection Projects