214
R.H. Charlier and Chr. P. De Meyer
This revetment is permeable, takes on the sott terrain's shape and absorbs wave
energy while successfully resisting the strongest currents. Several layers can be
placed on top of one another and tied together with wire. However, gabions are
poor protection for the beach itself as they may reduce or prohibit accretion by
sand of terrestrial origin. It has then been suggested to complement the use of
gabions by traditional constructions (groins, etc), by by-passing, by dune building
or planting, or simply by renourishment (fig. 26). Gabion breakwaters have been
constructed along East Coast Park on the southeastern coast of Singapore.
2.1.7
Artificial Reefs
Denmark and England put both claim for the earliest development of erosion
control through use of artificial seaweed. Field attempts were made in Denmark
and New Jersey. In the latter location bundles were placed along 275 m (900 ft)
of shoreline 245 m (800 ft) offshore in 4.5 m (15 ft) deep water making a 27.5 m
(90 ft) wide barrier. No conclusions could be drawn on the effectiveness. Later
experiments were conducted in the same countries, The Netherlands, Germany,
Norway and France ~Sa. Recently, Japan has used them as protective devices.
In The Netherlands and France positive results were achieved in reducing
scouring near man-made structures and improvements could be made by
lengthening the fronds and increasing their density in the bundles. In the United
States emphasis was placed on reducing shoreline erosion. Experiments at Fort
Belvoir, VA, at Cape Hatteras Lighthouse, NC, Stone Harbor Point, NJ, Naples,
FL, and in about 50 other locations have been negative, or are manufacturers'
claims. A rather positive report by Hall has been seriously challenged ~8b.
Seaweeds effects, whether natural or artificial, have the greatest impact at and
close to the surface hence the most attractive approach by which they can be
effective is by reduction of incoming wave height. A seaweed barrier would act as
a floating porous breakwater. Where the artificial seaweeds are concerned the
European manufactured types appear to be of higher quality than their American
counterparts.
But artificial seaweeds fields present two disadvantages : an effective field, even
if placed so that it would not be a navigational or recreational hazard, would be
more expensive than other beach protection methods, and it appears to have
unfavorable effects upon beaches and shorelines further downdrift.
Although artificially, viz. by man, put in place, some "artificial reefs" are not
made of man made materials but use "natural" material.
R.H. Charlier and Chr. P. De Meyer
This revetment is permeable, takes on the sott terrain's shape and absorbs wave
energy while successfully resisting the strongest currents. Several layers can be
placed on top of one another and tied together with wire. However, gabions are
poor protection for the beach itself as they may reduce or prohibit accretion by
sand of terrestrial origin. It has then been suggested to complement the use of
gabions by traditional constructions (groins, etc), by by-passing, by dune building
or planting, or simply by renourishment (fig. 26). Gabion breakwaters have been
constructed along East Coast Park on the southeastern coast of Singapore.
2.1.7
Artificial Reefs
Denmark and England put both claim for the earliest development of erosion
control through use of artificial seaweed. Field attempts were made in Denmark
and New Jersey. In the latter location bundles were placed along 275 m (900 ft)
of shoreline 245 m (800 ft) offshore in 4.5 m (15 ft) deep water making a 27.5 m
(90 ft) wide barrier. No conclusions could be drawn on the effectiveness. Later
experiments were conducted in the same countries, The Netherlands, Germany,
Norway and France ~Sa. Recently, Japan has used them as protective devices.
In The Netherlands and France positive results were achieved in reducing
scouring near man-made structures and improvements could be made by
lengthening the fronds and increasing their density in the bundles. In the United
States emphasis was placed on reducing shoreline erosion. Experiments at Fort
Belvoir, VA, at Cape Hatteras Lighthouse, NC, Stone Harbor Point, NJ, Naples,
FL, and in about 50 other locations have been negative, or are manufacturers'
claims. A rather positive report by Hall has been seriously challenged ~8b.
Seaweeds effects, whether natural or artificial, have the greatest impact at and
close to the surface hence the most attractive approach by which they can be
effective is by reduction of incoming wave height. A seaweed barrier would act as
a floating porous breakwater. Where the artificial seaweeds are concerned the
European manufactured types appear to be of higher quality than their American
counterparts.
But artificial seaweeds fields present two disadvantages : an effective field, even
if placed so that it would not be a navigational or recreational hazard, would be
more expensive than other beach protection methods, and it appears to have
unfavorable effects upon beaches and shorelines further downdrift.
Although artificially, viz. by man, put in place, some "artificial reefs" are not
made of man made materials but use "natural" material.