Environmental Engineering Reference
In-Depth Information
Waste from a steelworks has been used to renourish beaches at Port Lincoln
and Port Augusta, in South Australia. Ships ballast was added to the beach in
Oriental Bay, on the north-east shore of Wellington Harbour, New Zealand, to
improve it for recreation.
4.2.10 Artificial Sediment
The possibility of using artificial sand for beach renourishment has been consid-
ered in Japan, where a laboratory has tried to produce foraminiferal sand (“star
sand”). Alternatively, broken glass (cullet) can be ground into sand-sized frag-
ments (Edge et al.
2002
; Makowski and Rusenko
2007
; Makowski et al.
2011
).
First proposed by Finkl (
1996
) for use on Florida's beaches, recycled glass cullet
has been found to retain the same physical properties as natural silica sand and can
be mechanically processed to match the grain size of the existing beach sediment.
Recycled glass has also been used on beaches along Lake Hood in New Zealand,
the Dutch Caribbean island of Curacao and Hawaii (Williams and Micallef
2009
).
4.3 Methods of Beach Renourishment
Methods of renourishing a beach vary according to the configuration of the coast and
the processes at work on it. Locations of renourishment within a beach also vary and
include dune nourishment; nourishment of the subaerial beach (berm), profile nourish-
ment (subaerial and submerged) and bar or shore face nourishment (submerged fill).
Direct placement of fill can be used on a coastal sector, particularly where
longshore drift is weak, or can be controlled by the insertion of groynes.
Renourishment should be at points or sectors from which it is expected that long-
shore drift will carry the sediment to where it is required. There is bypassing,
where sediment is conveyed from a sector that has prograded alongside an obsta-
cle such as a breakwater, a river mouth or a tidal inlet, along the coast to replenish
a beach depleted downdrift. There is recycling (Sect.
4.3.4
, p. 66), whereby beach
losses due to longshore drift are made good by bringing back the sediment. There
is nearshore renourishment based on the expectation of shoreward drift, and back-
passing, which is analogous to longshore recycling in that it brings back sediment
lost seaward from a beach. Offshore breakwaters have been used to renourish a
beach by inducing accretion in their lee, and some beaches have been emplaced or
reshaped by bulldozing. Each of these techniques will be considered and exempli-
fied in the following sections.
4.3.1. Direct placement
4.3.2. Emplacement by longshore drift
4.3.3. Bypassing
4.3.4. Recycling
