Environmental Engineering Reference
In-Depth Information
Fig. 6.2
Renourishment of Ettalong Beach, Broken Bay, Australia during November 2013.
Sediment dredged from the bay floor 1 km offshore is pumped onshore through a hydraulic pipe
and then placed in heaps along the sub-aerial beach by excavator. © Nick Lewis
the beach annually and comparing the result with the target profile before planning
more specifically where, when and how best to undertake subsequent work.
Long-term costs of beach renourishment projects are difficult to estimate. The
beach renourishment at Ocean City, New Jersey in 1982 (Sect.
4.3.8
, p. 73) did not
provide the expected benefits; it cost $2.5 million but lasted only two and a half
months (NOAA
2000
). As previously mentioned, reasons for such discrepancies in
performance can include poor project design, unanticipated coastal storm events,
or use of incompatible sand grain size. The unknown life of the rebuilt beach and
the resulting need for maintenance renourishment are two causes of uncertainty in
determining long-term costs and benefits.
Coastal planners should compare estimates of the costs of beach renourish-
ment to the costs of alternatives, such as solid structures or managed retreat. The
costs of beach renourishment are generally lower and more evenly spread over
time than those incurred with the building of solid structures, which also require
maintenance, especially after they are damaged by storms. Renourished beaches
are more flexible than artificial structures because the beach profile can adapt to
hydrodynamic variations, such as cut-and-fill sequences or storm events, with-
out the damage caused to sea walls, groynes and other structures. In Port Phillip
Bay, Australia, the cost of beach renourishment does not exceed that of building
