306
3.2
R.H. Charlier and Chr: ' p. De Meyer
Role of Dunes in the Littoral System
A string of dunes is an important protective barrier for coastal properties ; the
share of the foredune is evidently primordial in this scheme. After a storm the
rebuilding process of beach and dune is far slower than erosion, and recovery
may even never occur particularly where waves are fetch-limited.
Other factors than storms can affect the system. So, in some sites beach material
can be picked up by winds, carried landward and be entirely removed from the
beach system.
Foredunes may occasionally be artificially heightened to avoid overtopping and
flooding is unlikely as long as the lagoon's width is less than 8 km (5 mi). In
other cases pre-construction investigation is indicated.
Revetments have sometimes been placed in front of dunes to protect the existing
slope face. They are a protective armor, not a retaining structure. They are less
damaging than sea-walls which cause frequently removal of sand.
Artificial sand dune building has gained much favor to remedy failed natural
defenses ; the dune is a flexible last line. Sand dunes can be built artificially by
placing permeable screens, 1 m (3 ft) high, half open. Once buried new ones can
be placed on top. To anchor the dune marram grass, cf.d grass, shrub buckthorn
and trees of the conifers family can be planted or sown. Beach nourishment has
also gained acceptability as a dissipater of wave-energy. In contrast to hard
structures, compensating the deficiency in the natural sand supply, remedies the
erosion cause and benefits adjacent shores.
Where the dune/beach system protects shore constructions, hard protective
structures may often be dispensed with. Such massive protection works aim to
prevent waves to reach a shore or a harbor (sea-walls, breakwaters, bulkheads
and revetments, p. ex.), or to slow down longshore drift (jetties, groins).
3.3
Failure of a dune system
The failure mechanisms of a dune are fairly similar to the mechanisms for dikes
(cf. fig. 37) Erosion of the outer slope is however essentially different. The body
of the dune contains enough material to take a special shape during storm-surges
: "the storm profile".
3.2
R.H. Charlier and Chr: ' p. De Meyer
Role of Dunes in the Littoral System
A string of dunes is an important protective barrier for coastal properties ; the
share of the foredune is evidently primordial in this scheme. After a storm the
rebuilding process of beach and dune is far slower than erosion, and recovery
may even never occur particularly where waves are fetch-limited.
Other factors than storms can affect the system. So, in some sites beach material
can be picked up by winds, carried landward and be entirely removed from the
beach system.
Foredunes may occasionally be artificially heightened to avoid overtopping and
flooding is unlikely as long as the lagoon's width is less than 8 km (5 mi). In
other cases pre-construction investigation is indicated.
Revetments have sometimes been placed in front of dunes to protect the existing
slope face. They are a protective armor, not a retaining structure. They are less
damaging than sea-walls which cause frequently removal of sand.
Artificial sand dune building has gained much favor to remedy failed natural
defenses ; the dune is a flexible last line. Sand dunes can be built artificially by
placing permeable screens, 1 m (3 ft) high, half open. Once buried new ones can
be placed on top. To anchor the dune marram grass, cf.d grass, shrub buckthorn
and trees of the conifers family can be planted or sown. Beach nourishment has
also gained acceptability as a dissipater of wave-energy. In contrast to hard
structures, compensating the deficiency in the natural sand supply, remedies the
erosion cause and benefits adjacent shores.
Where the dune/beach system protects shore constructions, hard protective
structures may often be dispensed with. Such massive protection works aim to
prevent waves to reach a shore or a harbor (sea-walls, breakwaters, bulkheads
and revetments, p. ex.), or to slow down longshore drift (jetties, groins).
3.3
Failure of a dune system
The failure mechanisms of a dune are fairly similar to the mechanisms for dikes
(cf. fig. 37) Erosion of the outer slope is however essentially different. The body
of the dune contains enough material to take a special shape during storm-surges
: "the storm profile".