Frequently Asked Questions (FAQs)

What is coastal erosion?

Coastal erosion is the encroachment upon the land by the sea and is measured by averaging over a period, which is long enough, to eliminate the impacts of weather, storm events and local sediment dynamics.

Coastal erosion results in three different types of impacts (or risks): 

  • Loss of land with economical, societal or ecological value 
  • Destruction of natural sea defences (usually a dune system) as a result of a single storm event, which in turn results in flooding of the hinterland. 
  • Undermining of artificial sea defences, potentially also leading to flood risk.

The processes of coastal erosion and accretion have always existed and have contributed throughout history to shape European coastal landscapes,creating a wide variety of coastal types. Erosion of inland soils induced by rainfall and movement along riverbeds provides in some areas considerable amounts of terrestrial sediments to the coast. These sediments together with those derived from coastal features (such as eroding cliffs and marine sand banks) provide essential material for the development of offshore reefs, mud flats,saltmarshes, sandy beaches, sand dunes, and transitional marshes. In turn, these coastal habitats provide a wide range of outstanding benefits including locations for economic and recreational activities, protection from flooding in low lying areas, absorption of wave energy during storm surges, reduction of eutrophication of coastal waters, as well as nesting and hatching of fauna species. Combating coastal erosion can therefore create new problems elsewhere, depending on the type of measures taken.

Coastal erosion is usually the result of a combination of factors - both natural and human induced - that operate on different scales. Most important natural factors are: winds and storms, near shore currents, relative sea level rise (a combination of vertical land movement and sea level rise) and lope processes. Human induced factors of coastal erosion include: coastal engineering, land claim, river basin regulation works (especially construction of dams), dredging, vegetation clearing, gas mining and water extraction. (source: www.eurosion.org)



What are the impacts of climate change on coastal erosion? 

The main factor influencing the rates of coastal erosion is Portugal is the reduction in the amount of sediment that reaches the sea (due mostly to the construction of dams on rivers and sand extraction), but also due to some of the phenomena that characterize climate change, particularly sea level rise and the rotation of the direction of the waves, which has strong implications on the north-south sediment drift along the Portuguese west coast. Some scenarios point to a 12 to 15% intensification of coastal erosion until 2100. Therefore the impacts of climate change will add to the already accelerated coastal erosion process of the Portuguese coastline. (Source: SIAM II project).