Coastal erosion: Béchu presents national scenarios and national maps, as well as the consequences for coastal territories

Today the scenarios, data and maps available to us thanks to Cerema reveal the need for anticipation. Consideration must be given to measuring and organizing national solidarity now in order to collectively anticipate the potentially destabilizing effects of climate change on our coastlines. This is the meaning of the work carried out by the National Coastline Council, meeting once again on Thursday April 4. This work will feed into the draft third National Plan for Adaptation to Climate Change (PNACC 3).

According to Cerema, on the scale of France as well as the overseas departments and regions:

• By 2028, a thousand buildings would be affected by the retreat of the coastline, mainly residential (300) and commercial (190) buildings. Those that can be estimated have a market value of around €235 million. At this time, Cerema identified the buildings located in the immediate vicinity of the coastline and potentially exposed to “event-related setback”: marked setback during storms, landslides, etc. This is a likely scenario: although it does not mean that all the buildings will go into the sea, these buildings are close to receding or unstable areas.
• By 2050, 5.200 homes would be threatened, including 2.000 second homes, with a market value estimated at €1,1 billion. Also at this deadline, 1.400 business premises would be affected for a market value estimated at €120 million. 2050 constitutes a scenario integrating the continued trend of the coastline retreat and based on the maintenance in place and maintenance of all the works coastal protection: this is an objective and likely scenario.
• By 2100, there are 450.000 housing units with a market value of €86 billion, 55.000 business premises with a market value of €8 billion, 10.000 public buildings, 1 km of roads and 800 km of railways which could be impacted if nothing is done. 240 is a scenario of inaction (complete disappearance of coastal defense structures and the progressive flooding of all topographically low areas of the coastline). At this deadline, Cerema is based on a high estimate from the IPCC and assumes a possible rise of 2100m in sea and ocean levels. The phenomenon has continued to increase since the beginning of the 1th century and this phenomenon is expected to accelerate.

Access Cerema studies

Coastline projection and analysis of issues at national level - 5-year deadline

Coastline projection and analysis of issues at national level - Horizons 2050 and 2100

2050 and 2100 cards

Context and points of attention

The reports produced by Cerema provide a better understanding of coastal erosion on the scale of France and overseas (DROM). As a reminder, the national indicator of coastal erosion produced by Cerema indicates that nearly 20% of the coasts are currently in retreat, or around 900 km.

This work was carried out specifically for the ongoing reflections of the National Coastline Committee (CNTC) and in particular to feed the IGEDD-IGA report published on March 8 on the issue of financing the consequences of the retreat of the coastline.

If the figures appear precise and are presented by department in the reports, the results can only be interpreted on a national scale. They must be considered as orders of magnitude and trends in order to feed the CNTC's reflections. They are not relevant at the sub-departmental level.

These national studies are not based on detailed knowledge of local mechanisms of coastal erosion and the results should therefore not replace knowledge in the region, in particular the work underway by certain local exposure mapping communities.

The estimated value is only the current market value of the buildings (the value of the walls and not that of the business in particular).

Work will continue within the framework of PNACC 3: updating the national coastline indicator, work on understanding coastal structures, supporting communities for their local mapping, etc.