Built-over areas

The built-over areas are the parts that are no longer submerged. This is the direct impact of construction on the sea bottom. The under-sea habitats that have been built over are thus irreversibly destroyed. The landward delimitation of the built-over area is based on the original coastline (natural). It should be pointed out that we have not taken into account submerged parts of constructions or pontoons built on piles.

En grisé les surfaces couvertes
The built-over areas

Enclosed water area

The enclosed water area corresponds to the body of water enclosed by construction (port, port of refuge, artificial beach). The delimitation of the enclosed water area is based (i) on the seaward side, by the ends of the seawalls (ii) on the landward side, by the inner contour of the jetties quays or rockfill. The enclosure of this water mass irreversibly upsets the enclosed ecosystems. The body of water, in particular in the case of harbours, is the receptacle of various kinds of pollution such as heavy metals (from anti-fouling paint on boats), hydrocarbons, macro-detritus and various organic substances (from waste water from inhabited boats). Given that the ecosystems originally situated on these spaces have been definitively enclosed by the constructions and have been irreversibly destroyed or disturbed, these areas are taken into account for calculation of the ecological impact rate.

Exemple de plan d’eau endigué.
Example of an enclosed area of water.


Area reclaimed from the sea

This is the sum total of the surface area of built-over areas and enclosed bodies of water.


Coupe transversale d'un port montrant la surface gagnée (les surfaces couvertes + surfaces de plan d’eau endigué)

Cross-section of a harbour showing the reclaimed area (built-over areas + enclosed bodies of water)

Particular cases

Areas of water in spaces excavated on land. When a construction has been built by digging part of the space for a body of water out of the land, we have dissociated the ‘excavated body of water’ from the ‘enclosed body of water’; only the ‘enclosed body of water’ has been taken into account for the ecological impact calculations

Accumulations of sediment caused by construction. This is the surface area representing the emerged part of the sediment accumulated against a construction because of alteration of the currents and local hydrodynamic forces. These surface areas are not taken into account in the impact assessment since they are mobile sediments that may have come from the erosion of another part of the coast (in cases where the marine domain is extensive).


 Exemple d’accumulation de sédiments contre un port.
Example of accumulation of sediment against harbour structures.