Environmental Engineering Reference
In-Depth Information
Fig. 4.24b
Sand heaps delivered to the depleted southern end of the beach at Glenelg, Adelaide
for beach renourishment. © Geostudies
(Schwartz and Musialawski
1977
). The project indicated that if sufficient sand is
deposited in the nearshore zone it will move shoreward from a specific depth, but
that longshore drift will determine which sectors of the beach receive it.
On the Gold Coast in Queensland, Australia 100,000 m
3
of sand was dredged
from the sea floor 1.5 km off Burleigh Heads (where the water is 18-25 m deep)
in 1985, brought in and dumped on sand bars in the nearshore zone. Within a year
much of this sand had been washed on to the beach.
A similar method was utilised in the Hythe Coast Protection Scheme in
Kent,United Kingdom where it was demonstrated that by placing the replenish-
ment sediment in one location on the beach face and allowing the beach to sort
naturally, without labour-intensive re-profiling, the duration (construction) and
cost of recycling was significantly reduced (Clarke and Brookes
2008
).
4.3.6 Backpassing and Beach Re-shaping
Losses of sediment seaward from a beach, particularly during stormy phases, can
be offset by backpassing, the retrieval of beach material that has been swept off-
shore and its return to the beach. This is analogous to recycling of beach material
