Coastline under erosion

The "Coastline under erosion" fact sheet assesses the extent of shoreline in low-lying sandy areas subject to erosion/retreat.

Coastal erosion is the removal and detachment of sediments from beaches, dunes and sea cliffs due to the join action of oceanographic forcing factors (i.e., waves, currents and tides), resulting in coastline retreat and, subsequently, in the loss of land.

Coastal erosion can occur over short-term periods (e.g., instant shoreline retreat associated with storms), depending on seasonal variability, or over longer periods of time, at the inter-annual or decadal scale.

Causes for coastal erosion are both natural and human induced, most notably the decrease in the supply of sediments to the shoreline, due to the regulation of rivers, the existence of hard engineering structures and sea level rise.

To calculate the indicator, we consider the extension (i.e. length) of low-lying sandy coast under erosion or with erosion as dominant trend.

The indicator is expressed in length (running km) of coastline under critical erosion.

This indicator concerns mainland Portugal and shall be updated on an annual basis.

Objectives and targets: 

One of the objectives of the 2nd generation of Shoreline Management Plans and the Portugal´s Coastal Monitoring Programme (COSMO) (due to start early in 2017) is to update and detail the information regarding shoreline evolution, namely the identification of areas subject to coastal erosion and quantification of retreat.

The results obtained in these programmes are aimed at identifying and regularly monitoring all the sites subject to coastal erosion and with an observed coastline retreat in low-lying sandy areas.

This data is crucial for outlining evolutionary trends in a context of climate change, as well to support decision making at various levels and within different scopes.

Progress analysis:

This indicator is based on the existing shoreline evolution/retreat data, namely from unpublished internal studies by the Portuguese Environment Agency, Shoreline Management  Plans Characterisation Studies, expert technical and scientific publications, as well as Master's and PhD theses. In the future, this information will be updated with data from the Portugal´s Coastal Monitoring Programme (COSMO).

Last update: 
Monday, 7 August, 2017