310
R.H. Charlier and Chr. P. De Meyer
A single groin has the same interaction with the littoral system as a jetty, but a
field of parallel groins favors beach formation. Groins being shorter than jetties,
longshore transport continues ahead of the toe. Nevertheless a groin field merely
transfers downdrifl the erosional problem : a classical example is found at Long
Beach, NY. Effectiveness of a field with minimized "negative" impact is achieved
by concomitant artificial nourishment. By-passing schemes are often a good
approach to solve the problem ; they involve dredges, sometimes a dredge
protecting breakwater, or a scheme with a deposition basin.
Morphology can play a part in jetty-induced erosion on a coast with no littoral
drift. Indeed, erosion factors in this instance encompass the embayment size
between pre- and post-jetty shorelines, and shoreline length undergoing sand
withdrawal towards a jetty-close area which has to fill to achieve a new shoreline
equilibrium. Evidently, equilibrium is eventually reached, which is never the case
there where a littoral exists.
In conclusion, any structure that modifies artificially an existing shoreline
disturbs an existing equilibrium and its presence will result in erosion and
accretion phenomena.
As repeatedly underscored in the preceding chapters, all structures, and remedies,
are temporary as only nature could halt coastal erosion. To insure the continued
effectiveness of protective measures sustained monitoring and careful
maintenance must be carried out. One may include either as "measure" or as
"maintenance" the prohibition of practices which result in renewed or intensified
erosion, such as mangrove conversion along mud coasts, destruction of coral
reefs (an irreversible "damage"), "development" or reclamation of wetlands,
poorly planned implantation of constructions at sea or land extensions for
whatever purpose(s). On the other hand regular profiling and surveying of
regions which have been artificially nourished, dewatered, "replanted" or
otherwise protected is necessary both to ascertain de facto results of the
"intervention" and to identify steps needed to sustain the effects of the
engineering work undertaken. Where hard structures are concerned maintenance
and repairs must guarantee not only their effectiveness but their very own
"survival".
R.H. Charlier and Chr. P. De Meyer
A single groin has the same interaction with the littoral system as a jetty, but a
field of parallel groins favors beach formation. Groins being shorter than jetties,
longshore transport continues ahead of the toe. Nevertheless a groin field merely
transfers downdrifl the erosional problem : a classical example is found at Long
Beach, NY. Effectiveness of a field with minimized "negative" impact is achieved
by concomitant artificial nourishment. By-passing schemes are often a good
approach to solve the problem ; they involve dredges, sometimes a dredge
protecting breakwater, or a scheme with a deposition basin.
Morphology can play a part in jetty-induced erosion on a coast with no littoral
drift. Indeed, erosion factors in this instance encompass the embayment size
between pre- and post-jetty shorelines, and shoreline length undergoing sand
withdrawal towards a jetty-close area which has to fill to achieve a new shoreline
equilibrium. Evidently, equilibrium is eventually reached, which is never the case
there where a littoral exists.
In conclusion, any structure that modifies artificially an existing shoreline
disturbs an existing equilibrium and its presence will result in erosion and
accretion phenomena.
As repeatedly underscored in the preceding chapters, all structures, and remedies,
are temporary as only nature could halt coastal erosion. To insure the continued
effectiveness of protective measures sustained monitoring and careful
maintenance must be carried out. One may include either as "measure" or as
"maintenance" the prohibition of practices which result in renewed or intensified
erosion, such as mangrove conversion along mud coasts, destruction of coral
reefs (an irreversible "damage"), "development" or reclamation of wetlands,
poorly planned implantation of constructions at sea or land extensions for
whatever purpose(s). On the other hand regular profiling and surveying of
regions which have been artificially nourished, dewatered, "replanted" or
otherwise protected is necessary both to ascertain de facto results of the
"intervention" and to identify steps needed to sustain the effects of the
engineering work undertaken. Where hard structures are concerned maintenance
and repairs must guarantee not only their effectiveness but their very own
"survival".