2.3 Coastal defences

One of the problems most felt along the coast is the beaches erosion that threatens the urban settlements and tourism attractions. The origins of the phenomenon are many, some are natural, such as the action of the sea and the wind, others are due to human interventions, such as the removal of sand in riverbeds or the subsidence deriving from the groundwater exploitation.

In the attempt to locally contrast the phenomenon, two main methods are used: the beach nourishment and armour rock for coastal defences (FIG1_SES2.3).

Fig1_SES2.3 Coastal defences, Portland harbour. by Claus Ableiter, Bild von User:Mark.murphy – wiki-en, Beitrag von User:Mark.murphy, CC BY-SA 3.0,

A coastal defence is a man-made wall placed in a given area and used for various purposes: to slow down the coastal erosion, to help the fish repopulation (FIG2_SES2.3) or underwater recreational development.

Fig2_SES2.3 Artificial refuge. Associazione Blennius

Instead abandoned structures like a wreck (FIG3_SES2.3) or a platforms may serve as artificial barriers; in different periods, all of them are quickly colonized by plants and marine animals and become particularly attractive for pioneering species (VIDEO1_SES2.3).

Life on artificial barriers. Associazione Blennius

Infact, steel structures such as methane or oil platforms are often colonized by filtering marine organisms such as mussels, oysters, tunicates and sponges and around this substratum other predators aggregate.

Fig3_SES2.3 Benthic organism on submerged wreck. Eva Turicchia

The material of which the barrier is made is really important, because the degradation due to the seawater can lead to the release of harmful substances for the life of the ecosystem.