14
S.D.King
to either directly fill a depleted beach zone or gradually feed a beach over time. This
method is becoming extremely attractive because it does not involve the construction of
costly structures, and can result in a more natural appearance. For example, in the
Netherlands, sand nourishment has been chosen as the main method of alleviating
erosion. Since 1991, about
of sand has been added to the Dutch coast, and
has proven to be a successful system (de Ruig, 1995).
Beach nourishment is not a straightforward process and “the techniques are
more sensitive than is commonly envisaged” (Carter, 1988, p. 459). Sources of fill have
to be selected with care so that they will merge with the indigenous material. It should
also be of similar or slightly larger size so as not to initiate new and unstable conditions.
The Dutch, for example, take sediment from the floor of the North Sea (de Ruig, 1995).
There are considerable benefits to beach nourishment if it is carried out correctly.
Adding sediment to the beach increases its natural volume, therefore counteracting
foreshore erosion. Where used in front of a sea wall, it will protect the wall toe and
foundations, preventing subsidence. In addition, control over longshore dispersal is
possible. Beach nourishment provides sediment for longshore drift, which may benefit
areas through natural accretion. In the Netherlands, where beach nourishment is now the
main method of defence, it has been found to be “effective in coastline preservation and
assists recreation, natural values and the flood protection system” (de Ruig, 1995, p.
254).
Beach nourishment may often be the best method of future defence as it fits
many of the criteria of MAFF. However, although it seems to benefit natural processes
such as sediment dispersal, it could have other environmental impacts and may be
economically unacceptable. Both at the source site and the nourishment site, disturbance
occurs which could be either temporary or permanent. For example, Loffler and Coosen
(1995) suggest that extraction of sand increases suspended sediment that in turn
increases turbidity. Prolonged turbidity affects the depth to which light can penetrate the
water, inhibiting the growth of plankton and algae. Benthic organisms disappear during
extractions, although mobile animals are less affected. At the nourishment site,
replenishment material is generally deposited in a horizontal layer. If the layer is greater
than 0.5 metres thick, the original benthic animals on the beach will die. This has an
adverse affect on the availability of food for birds, yet eventual damage may not be too
serious, and there are guidelines over the best time of year and the type of material for
nourishment. Overall, de Ruig (1995) concludes that “the ecological effects of sand
nourishments, both at the borrow and nourishment sites, seem to be minor” (de Ruig,
1995, p. 257). Economically, beach nourishment may be costly. The scheme allows for
sediment dispersal, and, therefore, beaches require annual replenishment and
maintenance, which means high labour costs.
In general “nourishment is an important competitor, it can be utilised virtually
anywhere, is easy to adapt with regard to sand volumes applied and it allows spreading
of costs of coastal protection” (de Ruig, 1995, p. 260). However, there needs to be
careful consideration of its environmental consequences and possible costs before it is
used.
S.D.King
to either directly fill a depleted beach zone or gradually feed a beach over time. This
method is becoming extremely attractive because it does not involve the construction of
costly structures, and can result in a more natural appearance. For example, in the
Netherlands, sand nourishment has been chosen as the main method of alleviating
erosion. Since 1991, about
of sand has been added to the Dutch coast, and
has proven to be a successful system (de Ruig, 1995).
Beach nourishment is not a straightforward process and “the techniques are
more sensitive than is commonly envisaged” (Carter, 1988, p. 459). Sources of fill have
to be selected with care so that they will merge with the indigenous material. It should
also be of similar or slightly larger size so as not to initiate new and unstable conditions.
The Dutch, for example, take sediment from the floor of the North Sea (de Ruig, 1995).
There are considerable benefits to beach nourishment if it is carried out correctly.
Adding sediment to the beach increases its natural volume, therefore counteracting
foreshore erosion. Where used in front of a sea wall, it will protect the wall toe and
foundations, preventing subsidence. In addition, control over longshore dispersal is
possible. Beach nourishment provides sediment for longshore drift, which may benefit
areas through natural accretion. In the Netherlands, where beach nourishment is now the
main method of defence, it has been found to be “effective in coastline preservation and
assists recreation, natural values and the flood protection system” (de Ruig, 1995, p.
254).
Beach nourishment may often be the best method of future defence as it fits
many of the criteria of MAFF. However, although it seems to benefit natural processes
such as sediment dispersal, it could have other environmental impacts and may be
economically unacceptable. Both at the source site and the nourishment site, disturbance
occurs which could be either temporary or permanent. For example, Loffler and Coosen
(1995) suggest that extraction of sand increases suspended sediment that in turn
increases turbidity. Prolonged turbidity affects the depth to which light can penetrate the
water, inhibiting the growth of plankton and algae. Benthic organisms disappear during
extractions, although mobile animals are less affected. At the nourishment site,
replenishment material is generally deposited in a horizontal layer. If the layer is greater
than 0.5 metres thick, the original benthic animals on the beach will die. This has an
adverse affect on the availability of food for birds, yet eventual damage may not be too
serious, and there are guidelines over the best time of year and the type of material for
nourishment. Overall, de Ruig (1995) concludes that “the ecological effects of sand
nourishments, both at the borrow and nourishment sites, seem to be minor” (de Ruig,
1995, p. 257). Economically, beach nourishment may be costly. The scheme allows for
sediment dispersal, and, therefore, beaches require annual replenishment and
maintenance, which means high labour costs.
In general “nourishment is an important competitor, it can be utilised virtually
anywhere, is easy to adapt with regard to sand volumes applied and it allows spreading
of costs of coastal protection” (de Ruig, 1995, p. 260). However, there needs to be
careful consideration of its environmental consequences and possible costs before it is
used.