Beach Renourishment Principles - Beach Renourishment - page 73

Fig. 4.26 Improvement of
the recreational beach at
Whitburn Bay, Durham, by
dumping sand over shingle.
© Geostudies
sediment (Finkl and Walker 2004 ). Veneer renourishment has been used at Corpus
Christi, Texas and Grand Island, Los Angeles, USA (NRC 1995 ).
4.3.10 Use of Structures
It is common for beach renourishment projects to include supporting structures in
an attempt to reduce the rate of losses and improve performance. For example, it
may be necessary to build groynes to retain a renourished beach on a coast dom-
inated by longshore drift. Sand and gravel drifting eastward from Bournemouth
augmented beaches as far as Hengistbury Head, where a terminal groyne was built
to intercept the drifting sediment to widen the beach and protect the backing cliffs
from further erosion (Fig. 3.4 ) .
In Monterey Bay, California, sand from a quarry was dumped on the shore
alongside a retaining groyne built at Capitola to prevent losses downdrift (Griggs
1990 ). Reference has been made to groynes built to retain renourished beaches at
Seaford in England and Mentone, Brighton and Sandringham in Port Phillip Bay,
Australia.
When shingle dredged from the sea floor was brought into renourish a depleted
beach in front of the sea wall at Lodmoor, east of the seaside resort at Weymouth
in Dorset in 1995, there was a possibility that during south-easterly storms shingle
from the augmented beach would drift westward on to the sandy resort beach. In
order to prevent this, a T-shaped retaining groyne was constructed at Melcombe
Regis, at the western end of the renourished beach.
The disadvantage of groynes is that they generally result in erosion down-
drift. On Sandy Hook, New Jersey, the shore had been protected by an 11 km sea
wall, to which groynes were added, but erosion beyond the end of these structures
began to cut out a bay. In 1977 152,920 m 3 of sand was trucked in and depos-
ited in the bay to provide protection from storm damage, but it soon drifted away
northward (Nordstrom et al. 1979). It would have been possible to go on extending
the groyne field downdrift, but Nordstrom and Allen ( 1980 ) suggested it might be