Environmental Engineering Reference
In-Depth Information
The beach was renourished in 1980-1983, using crushed limestone gravel
to form a sloping terrace, which soon acquired a veneer of inwashed fine to
medium sand. The coarse gravel thus provided a matrix for sustained sand
accretion, as well as increasing shore protection (Evangelista et al.
1992
).
Many seaside resorts have sought to renourish their beaches to improve the sea-
side environment. Cairns in north-eastern Australia has very little natural beach, the
esplanade being fronted by a large area of mudflats exposed as the tide ebbs. In 1993
the beach was augmented by bringing 4,000 m
3
of medium to coarse sand excavated
from a nearby delta, and depositing it between two temporary groynes in order to see
whether a beach could be maintained along the muddy seafront. It is difficult to keep
this beach clean, because it stands behind wide mudflats at low tide, and receives
muddy sediment when it is washed by turbid water at high tide. Similar problems
occur on the artificial resort beach of sand on Hamilton Island, Queensland, placed
on a shore cleared of mangroves, and passing to mud at low tide.
The placement of an artificial beach where none existed previously occurred on
the Algarve coast of Portugal (Fig.
4.18
). The shore at Praia da Rocha was cliffed
and mainly rocky, with only narrow pocket beaches, but in 1969-1970 880,000 m
3
of sand obtained from dredging the River Arade and excavation of the harbour at
Portimão was pumped on to the beach, and a further 150,000 m
3
added from these
Fig. 4.18
At Praia da Rocha on the Algarve coast of Portugal an artificial beach has been placed
in front of cliffs where no beach existed previously. Sediment dredged from the adjacent River
Arade was deposited on the shore to the west in 1970 and 1983, forming a very wide beach
above normal high tide level, incorporating several stacks. © Geostudies
