Erosion

Coastal erosion is the natural process responsible for the reduction of beaches, the retreat of dunes and cliffs. It shapes the coast by the action of waves, currents and wind.

On rocky coasts, it is manifested by the excavation of the cliffs, which weakened by the infiltration of rainwater into the rock, leads to their collapse. Recall that, by definition, cliffs are forms of erosion, so they can only recede.

On coasts of soft sediment (sand, gravel), the balance depends on the amount of material that is deposited on the shore from other sources (sandbanks, other beaches, eroded cliffs, etc.) and the amount that escapes. If the sediment balance is positive, the shore advances towards the sea (accretion). If it is negative, the coast recedes (erosion). The current period is characterized by a shortage of coastal sediments since the reserve formed during the last ice age is now almost consumed. This is why many European sedimentary coasts are subject to erosion.

Coastal erosion occurs mainly when winds are violent, large waves and at high tide episodes with big coefficients, especially if the storm drives these energies towards the coast in the form of storm waves (acute erosion). Along time, the succession of stormy episodes can lead to a sharp decline in the coast width (structural erosion).

The rate of erosion is measured in volume / length / time (e.g. m3/m/year), but since it is often used to show the rate of coastal decline, it is generally expressed in m/year. The speed of retreat depends on many factors (type of coast, energy of the waves and the tides, etc.) and can be from a few centimeters to tens of meters per year.

Human influence on the coastal zone has turned the natural phenomenon of coastal erosion into a social problem of increasing intensity. Urbanization and economic activities are very important on coastal areas, which leads to coastal engineering, river basin regulation (particularly dams), dredging, land clearing, extraction of marine aggregates, sand, natural gas, water and land occupancy requests (EUROSION, 2004), which together aggravate the erosion phenomenon in areas where it already existed naturally, but which sometimes lead to the decline of the coast in areas that were not affected by this natural phenomena.

Thus, coastal erosion is the result of a combination of factors, both natural and anthropogenic, that act at different scales.

It is important to keep in mind that the supply of sand needed to maintain beaches and coastal dunes depends on the erosion of other coastal areas and that these beaches and dunes are a very valuable natural defence against coastal flooding.

Resources

ANCORIM case studies

Gâvres Peninsula

(Cap Lorient, France)

Case of study : The Gâvres PeninsulaThe Lorient municipalities grouping organised the first case study days for the  ANCORIM programme on 6 and 7 October, 2010

Esmoriz-Cortegaça

(Portugal)

Case of study : Esmoriz-CortegaçaThis Case Study aims to evaluate alternatives for development planning and coastal defence to minimize erosion problems in the maritime boundaries of the two settlements.

ANCORIM tools

Overview of soft coastal protection solutions

Overview of soft coastal protection solutionsThis didactic tool offers a sample group of solutions to limit coastal erosion and advances the importance of «soft» solutions as much as possible.

Decision Making and Coastal Risks: A Good Practice Guide

Decision Making and Coastal Risks: A Good Practice GuideThe objective of this handbook is to provide a Good Practice Guide to facilitate the inclusion of coastal risk into decisions made in the coastal zone.

Other ressources
Case studies

EUCC Atlantic Center and the team of ARCOSLIFE Arenales Costeros project organized a field workshop in the Cantabrian dunes (Spain) on 25 and 26 April 2017. Two dune systems under strong human pressure, the dunes of Liencres and Somo, near Santander were studied

Scientists and local actors (elected officials, managers, practitioners and users) meet on a coastal site that is particularly interesting because of the problems of integrated management, protection of the natural environment and sustainable development that it raises.

Assessment and management tools

The RISC-KIT project developed the following tools to identify and prioritize the coastal zones which are most at risk.

The objective of the COCORISCO project was to understand the vulnerability of coastal territories to the risks of erosion and submergence and to move towards prevention and management strategies.

This toolkit is a practical guide to engaging communities on the issues of coastal erosion and sea level rise.

Studies and publications

Europe-wide study meant to provide quantified evidence that coastal erosion in Europe does constitute a problem of growing magnitude that public authorities do not always succeed in containing, hence to assess the needs for action.

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