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beaches, it is beneficial, but if the beach fill site is near a harbor there
is danger of sand moving into navigation channels, causing detrimental
shoaling.
3. A protective beach can be a recreation facility and improves access to
the water. Where dunes are included as part of the project, access across
the dunes may have to be restricted to prevent their being beaten down by
foot and vehicular traffic.
MATERIALS SELECTION: The source of the fill material is the primary deter-
minant of the method of placement, but environmental and economic factors
must be considered. Selection of a borrow site will depend to a great ex-
tent on the ecological impacts of using the site,
since many of the convenient
wetland areas are environmentally sensitive.
Sand, from underwater sources,
is usually pumped into place as a slurry, but such hydraulic placement tends
to wash away the finer materials in the borrow sand and cloud adjacent
waters. Due to this clouding, hydraulic placement is environmentally unac-
ceptable in some regions.
In these areas pumped sand may need to be ponded
and then distributed to the beach by scrapers.
This process requires addi-
tional area for the pond and access to the beach for construction equipment.
Sand, from upland sources, is usually placed using trucks and scrapers.
Fine sand generally erodes faster than coarse sand, but if coarse sand must
be transported long distances to the beach site, the high costs may be pro-
hibitive; therefore, the use of available, nearby sources of finer sand
may be the only practical choice.
If the offshore slope is steep, higher
volumes of fill would be required for a beach of
adequate dimensions and
this may cause the structure to be uneconomical.
Although providing pro-
tective beaches may be more economical initially than construction of
other coastal structures, if frequent replenishment is required, the
total
volume involved can reverse the economic advantage.
REFERENCES:
U.S. ARMY, CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, Shore
Protection Manual, 3d ed., Vols. I, II, and III, Stock No. 008-022-00113-
1, U.S. Government Printing Office, Washington, D.C., 1977, 1,262 pp.
U.S. ARMY CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, "Groins -
Their Applications and Limitations," CETN-III-10, Fort Belvoir, VA.,
1981.
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