EM 1110-2-1100 (Part V)
31 Jul 2003
characteristics of infrastructure and property, and the positions of structures relative to the present shoreline.
Historical surveys or charts are useful in determining the degree to which existing infrastructure encroaches
upon, or is seaward of, the historical beach location. Ground inspections and photos also can be used to
characterize the condition and value of structures.
(b) The presence of existing coastal structures, and their characteristics, are also important parameters.
What measures are already in place to provide protection to structures (e.g., seawalls and revetments), and
what is the condition and effectiveness of those structures? Structures that alter or block the alongshore
movement of sand, such as groins, detached breakwaters, or artificial headlands influence the pathways of
sand movement at the site. Crest elevation, composition, and condition of groins, revetments, and seawalls
determine the structures' functional effectiveness. The "signature" of impoundment adjacent to groins, or
lack thereof, can be an indicator of groin functionality. Aerial and ground photos can be used to characterize
the condition and effectiveness of existing coastal structures. Engineering drawings that show the subsurface
characteristics of the structures, including any toe protection, in concert with present beach profile surveys,
can be used to characterize the vulnerability of revetments and seawalls to damage caused by recession of
the beach during storms.
(7) Prior engineering activities.
(a) Usually, areas being considered for a beach nourishment project have experienced problematic
erosion for some time. Often, there is a record of previous studies and perhaps a record of past engineering
activities at the site. This information can shed light on what may or may not work in the future, and why;
and aid in designing a nourishment project. For example, records of past beach-fill activities can provide
information about expected fill longevity and net longshore transport rates. Historical records documenting
impoundment at groins can provide information about net longshore sand transport rates. Dredging and
placement records are vital information in the development of a sand budget. The record of past engineering
activities may also help explain a particular beach response that has been observed. Compiling a complete
chronology and record of past engineering activities can prove to be a very valuable design aid.
(b) This section briefly highlighted some of the more important aspects of project setting and site
characterization and history, and how they relate to design of beach nourishment projects. Subsequent
sections provide more detailed information about how these factors enter into the design process.
d. Reach delineation.
(1) In addition to the setting for a beach nourishment project and its design features, an equally important
design issue is delineation of sections of coast along which a project is to be constructed. Project economics
is often a controlling factor in the process of reach delineation. The values of property and infrastructure
assets fronting the beach and benefits gained by providing storm-damage reduction enter in assigning bounds
of a project reach or subreaches. Project boundaries may be determined by limits of political jurisdiction such
as municipal or state boundaries, or may coincide with physical features such as inlets or headlands.
Environmental considerations and local preferences may also influence project boundaries.
(2) From an engineering perspective, reach delineation should be evaluated based on physical processes
controlling project response. For example, location and characteristics of project terminal boundaries may
be evaluated on the basis of fill retention within project bounds and project impacts on adjacent shorelines.
Where reaches terminate along the open coast, fill transitions may be used to reduce the rate of spreading
losses from project bounds. Transitions may be placed either within or outside project bounds based on
design objectives and/or constraints. A more detailed discussion of beach fill transitions is provided in Part
V-4-1-h. In cases where reaches terminate at shore-normal structures (e.g., groins and jetties), effects of
interrupting littoral drift on downdrift beaches should be assessed. Whether boundaries occur at structures
Beach Fill Design