In coastal areas, the interaction between seawater and fresh water is in a dynamic equilibrium and occurs both in surface bodies (saltwater ingression) and in groundwater (saltwater intrusion in aquifers). Human actions and climatic changes, especially sea level rising, can alter this equilibrium leading to a contamination of the fresh water and soils by seawater.
The shift of salt wedge towards inland can be a consequence of both natural and anthropogenic processes. Natural processes have generally slow effects, except in the case of tsunami, as in Sri Lanka (Villholth and Neupane, 2011). The sea level rising due to climatic changes (Melloul and Collin, 2006) and local subsidence along coastal areas cause a slow salt wedge shifting. Instead, human actions have rapid effects on the coast system. Examples of the human actions are the overexploitation of aquifer, the incorrect and extreme watercourse regimentation, the excavation of floodway canal and dredging for navigation.
The salt wedge intrusion can lead to freshwater contamination and consequently to a decrease of water reserve, to coastal area desertification by ground salinization and to a loss of faunistic and floristic species.
