Marine aggregates: UNPG publishes a new guide

To answer this question, it is necessary to separate the direct and indirect effects, in time and space, of this activity on the evolution of the coastline.

Sand and gravel are no longer extracted from beaches and coastal areas. Contrary to some misconceptions, the current aggregate extraction operations off the French coast do not directly impact the coastline.
However, indirect effects cannot be ruled out, through modification of currents and sediment transport in the immediate vicinity of these operations.

To inform the debate and better guide the review of projects, the Ministry for Ecological Transition has assembled a committee of experts (Artelia, BRGM, Ifremer, Cerema, Shom) and, together with the National Union of Aggregate Producers (UNPG), is publishing a groundbreaking methodological guide. The result of three years of collaborative work, this document harmonizes existing knowledge and proposes a unified method for analyzing the potential indirect impacts of concessions on the coastline, intended for project developers, government agencies, and stakeholders.

The coastline, a living and complex interface

The coastline is not a fixed line: it is a zone of contact between land and sea, in constant motion. It can retreat (erosion) or advance (accretion), according to a sediment budget that depends on both inputs (marine and riverine) and losses (transfers to the open sea, development, urbanization, disturbances of sediment movements by human activities, etc.).

The guide also reminds us that we must distinguish between the coastal zone, which is very active, and the coastal zone further offshore, on the continental shelf, where the marine aggregate concessions are located: interactions exist, but they are not of the same intensity.

A structured, targeted… and local activity

Marine aggregate extraction in France remains modest in volume and is strictly regulated. Here are some key points:

• 8,7 million tonnes in 2022, representing approximately 2% of total national aggregate production;
• 17 active concessions, for an area of ​​approximately 160 km², or 0,04% of the metropolitan EEZ;
• an activity operated by 18 ships, representing approximately 900 direct and indirect jobs.

These materials meet specific technical needs, following a principle of resource efficiency: "the right material, in the right place, for the right use." Their role is particularly important for certain coastal areas, where they can represent 20 to 80% of the needs, as well as for metropolitan areas connected to the sea by rivers (Paris, Rouen, Nantes, Bordeaux), since aggregates are heavy materials whose transport cost is a determining factor.

A common method for assessing potential effects

The evaluation is based on a logic of comparison: a reference situation (current state) is compared with a situation at the end of operation, integrating, if necessary, the notion of cumulative effects with other projects.

The guide proposes to use four main models (sea states, currentology, coastal sediment transport, littoral transit), supplemented by optional modules for certain cases (estuaries, lagoons, etc.).

Important point: this framework is not intended to predict long-term coastal evolution, nor to assess the impact of new coastal developments (seawalls, groynes, beach nourishment). Rather, it serves as a reference tool to harmonize practices, enhance transparency, and disseminate a common base of scientific knowledge.

Ultimately, this guide represents a major step forward: it provides, for the first time, a method validated by a committee of experts (Artelia, BRGM, Ifremer, Cerema, Shom) to assess the potential indirect effects of marine aggregate extraction on the coastline.

Download the Guide in French and English from the UNPG website: sablesetgraviersenmer.fr