Environmental Engineering Reference
In-Depth Information
and sand settling quickly but the fine-grained silt and clay remaining in suspen-
sion. Cloudy water can diminish light penetration and so disadvantage sea floor
vegetation, while blanketing by spilt sediment has damaged seagrass communities,
coral reefs, and fish and shellfish resources.
Some of the early beach renourishment projects in the United States used sedi-
ment obtained from dredging nearby lagoons. These contained high proportions
of fine-grained sediment, the release of which buried, or proved damaging to,
sea floor biota (Reilly and Bellis
1983
). Later use of coarser sediment from off-
shore has caused less damage to estuarine and nearshore ecosystems (Marsh and
Turbeville
1981
; Lankford and Baca
1989
).
Mention has been made of problems of overland transportation, particularly
lorry traffic passing through seaside resorts.
6.1.3 Impacts of Beach Emplacement
The sand beach is a productive habitat, supporting dense concentrations of benthic
invertebrates that feed fishes, shore birds and crabs (Brown and McLachlan
1990
).
Sea turtles nest on some beaches. Renourishment of beaches can have ecological
impacts, as when previously rocky or muddy shore habitats are buried beneath
sand. The impacts of beach renourishment vary with location: offshore nourish-
ment will mainly affect benthic species and foraging birds, whereas backshore
renourishment will impact on terrestrial plants and animals (Speybroeck et al.
2006
).
Beaches, particularly sandy beaches, are ecosystems adapted to natural changes
caused by cut and fill and longshore drift, as well as tidal oscillations and fre-
quent variations in wave energy and turbidity. Ecosystems are modified as habitat
diminishes on eroding beaches, or as renourishment proceeds. Studies of ecologi-
cal changes on renourished beaches require monitoring of organisms on beaches
before and after renourishment (Nelson
1993
; Adriaanse and Coosen
1991
). At
Myrtle Beach in South Carolina sand quarried from inland was trucked to the
shore in early spring, and its deposition caused initial reductions in beach organ-
isms, but there was then rapid recovery and after four months some sites actually
showed species enrichment (Baca and Lankford
1988
).
At Palm Beach on Australia's Gold Coast macrofauna sampling was conducted
before and after the placement of 30,000 m
3
of sediment in November 2007. It
was found that macrofaunal communities were disrupted by the placement of sand
and associated works on the area (Noriega
2008
). Five months after renourishment
macrofauna improved and returned to pre-renourishment levels. Surf zone fish and
shore birds feed on macrofauna, so a decline in macrobenthic communities during
beach renourishment could have an adverse effect on these species.
The impact of beach renourishment on turtles in the United States has been
discussed by Dean (
2002
). Adverse impacts can include a harder and more com-
pacted beach due to the presence of finer sediment and a different sand colour,
