In France, no link can be established between offshore extraction and the evolution of the coastline

Their extraction, like all other anthropogenic activities, can have impacts. Known for a long time, they are taken into consideration in French regulations through specific legislation relating to both the mining code and the environment code. This activity is strictly controlled by State services. The publication of a recent study (2021) indicates that, thanks to compliance with criteria* established scientifically since the 80s, there is no proven impact of existing extraction sites on the evolution of the French coastline.

Improving and sharing knowledge: a strong ambition for the profession

For more than 40 years, professionals in the extraction of aggregates at sea have been involved in scientific partnerships in order to better understand and control the impact of their activity on the environment. More specifically, from the 1980s, they co-financed studies entrusted to the Laboratoire Central d'Hydraulique de France (LCHF), relating to the effect of an extraction cavity on the coastline. These concluded on the need to prohibit any concession within the littoral zone including the dune areas, the beaches and the underwater foreshores.

Several European and international research projects have enabled the French Research Institute for the Exploitation of the Sea (Ifremer) to generalize the previous conclusions and to initiate the drafting of a first guide published in 2007 issuing national recommendations for limit the effects of extractions on the coastline. These elements have been applied by the profession as scientific knowledge progresses and they are now included in numerical models which make it possible to quantify the effect of extractions by comparison between the reference state of the sites and the state after exploitation.

In addition, periodic monitoring of the funds of the concession and its surroundings are prescribed in the prefectural decrees for the opening of mining works.

A necessary focus on the exploitation of aggregates at sea and coastal erosion

Since 2012, the profession has also been involved in discussions on the “National strategy for the sustainable management of marine and land aggregates and quarry materials and substances” and participated in the working group on marine aggregates which drafted a guide methodology for the development of Orientation Documents for the Sustainable Management of Marine Aggregates (DOGGM) published in November 2016 by the Ministry in charge of the Environment.

On reading this guide, it appeared that the subject of the impact of the activity of offshore aggregates on the erosion of the coastline deserved a focus

The National Union of Aggregates Producers (UNPG), through the Marine Aggregates Commission, wanted to make available to all a scientific, technical and educational document which takes stock of the link between marine aggregate extractions and the evolution of the coastline.

The UNPG approached the public establishment Cerema and the consulting and engineering company Artelia to carry out an inventory of available knowledge.

The resulting report is organized into four chapters:

• Evolution of the coastline: general presentation of the subject,
• Synthesis of knowledge on certain sedimentary provinces of the North Sea, Channel and Atlantic facades,
• Synthesis of scientific knowledge on the different hydro-sedimentary processes that can lead to an impact of the extraction of marine aggregates on the coastline,
• Feedback from France.

This study carried out in 2021 by Artelia and Cerema indicates that, thanks to compliance with criteria scientifically established in the 80s to avoid potential impacts on the coastline, the concessions operated in France over the past forty years have been positioned correctly. As a result, there is currently no proven impact of existing sites on the evolution of the French coastline.

The UNPG wanted to go further after the publication of this study and approached the Ministry of Ecological Transition and Territorial Cohesion (MTECT) to complete it by writing and publishing a methodological guide submitted to the validation of a reading committee made up of experts on the subject. The aim is to provide a unified methodology for assessing the potential impacts on the evolution of the coastline, transposable to all types of concessions, depending on their context (coastal, estuarine, cliff sectors, etc.). This methodology will allow project promoters to better target their studies, the instructing departments to check the compliance of impact studies with this reference system and the stakeholders to have full transparency at their disposal an evaluation tool collectively recognized by experts from the topic.

The full study can be found here.

For Amélie Roche, project director in the management of coastal territories: “Cerema is the only public institution to embrace all coastal, maritime and river issues, providing expertise and solutions at national and territorial level. We have brought our expertise on the coastline and the impact of activities on the marine environment to the work with the UNPG. We participate in the committee of experts called upon by the MTECT to monitor the drafting of the methodological guide for assessing the impacts of the extraction of aggregates on the coastline. This is in line with our missions in favor of maritime spatial planning, which should make it possible to reconcile uses and limit pressures on the environment. »

For Luc HAMM, consultant in maritime hydraulics, former technical director of Artelia Branche Maritime: “This synthesis work has made it possible to gather and disseminate all the knowledge currently available at national and European level. It highlights the early implementation in France of practical recommendations to avoid any impact on the coastline, which have served as a basis for concession projects in France for 40 years. These recommendations then regularly evolved to follow scientific progress and in particular the development of digital simulations still in progress. »

For Laëtitia Paporé, president of the marine aggregates commission of the UNPG: “This study clarifies the involvement of the profession in the acquisition of knowledge on the potential impact of offshore mining on the coastline. It shows the evolution of the treatment of the subject in the impact studies of the application files for the exploitation of marine aggregates according to the evolution of scientific knowledge. This is an important first step in terms of sharing data and knowledge, followed by the ongoing development of the methodological guide. »