The Authie Bay, a coastal boundary between Pas-de-Calais and the Somme, is a Picardy-type estuary. It consists of an accreting shoreline (the poulier, on the southern bank) and an opposite shoreline with sections undergoing significant erosion (the musoir, on the northern bank).

Between 1258 and 1862, as the Poulier (southern bank) gradually accreted, humans built dikes (locally known as “renclôtures”) to progressively reclaim cultivable land from the salt marshes. In contrast, the northern bank has experienced (and continues to experience) significant erosion, particularly pronounced and visible at the Anse des Sternes, in the dune massif between the Bois des Sapins and the Bec du Perroquet. As for the schorre (or salt marshes), it is expanding through a slow process of silting and infilling of the bay.

On the northern bank, erosion of the dune ridge raises concerns about a possible breach that could threaten the low-lying lands located behind it with flooding (see: Coastal Risk Prevention Plan). This erosion results from a combination of factors: the natural evolution of the Poulier/Musoir system under the influence of waves and wind, the shifting of the Authie river’s main channel within its bay, and various structures built by humans over the past centuries. The sea and the Authie continuously shape the coastline. This estuary is part of a PAPI (Flood Prevention Action Program) initiative. To anticipate sea level rise linked to climate change, different scenarios have been studied, promoting the adoption of adaptive management strategies:

• Identify the essential infrastructure needed to ensure people’s safety and locate it effectively.
• Reconnect certain polders with the estuary to better support the evolution of the coastline.
• Design the developments by taking into account their overall effects, so that protections established in one area do not exacerbate erosion elsewhere.

Project actions and outcomes

These complex sediment exchanges create a wide variety of natural habitats (dunes, polders, salt marshes, hedgerow meadows, ponds, etc.). This complementarity of habitats provides a resting place for migratory birds and supports numerous human activities.

Balancing the protection of property and people, the continuation of traditional uses (hunting, agriculture, fishing), eco-tourism development, and the preservation of natural spaces requires a collective effort.

The Conservatoire du Littoral (french coastal protection agency) is involved in the resilient development of the bay. It is gradually acquiring land whose topography offers natural protection complementary to the dike system defined in the Flood Prevention Action Program (PAPI). The strategy is to use dunes and marshes as buffer zones in front of the flood defenses. At the back of the bay, the repositioning of dikes will restore areas for marine floodwater expansion. Near the Bois des Sapins, the construction of a setback dike will protect the area from flooding in case of dune breach. However, to prevent the formation of such a breach, the dune ridge—stabilized by pine planting in the 1960s—must regain its natural mobility.

The repositioning of these dikes will impact current uses (agriculture, hiking, etc.). To this end, meetings are held with local stakeholders to assess the consequences of different development options on economic activities and to find solutions. A territorial project is to be co-created around these new structures to enhance this land-sea interface.

Presented within a landscape approach, the land acquisitions by the Conservatoire du Littoral and the works of local authorities allow for the development of walking loops around the bay. At La Mollière (an agricultural polder created in 1850 and acquired in 2002), the Adapto project aims to improve the ecological quality of the estuary by creating resting, nesting, and feeding areas for birds. A comprehensive visitor management plan around the bay will define the works to be undertaken in the coming years to develop eco-tourism in this protected natural area.

Chronology

• May 7, 2015: Scientific Council, presentation of the Adapto approach and recommendations regarding natural risk management in Authie Bay.
• September 30, 2016: Site visit with elected officials to review completed developments and projects around Authie Bay – Landscape approach to better understand the need for a comprehensive work on the bay, both along the seafront and inland.
• August 2018: Coordination meeting for the various projects around the bay.
• October 10, 2018: PAPI BSA Steering Committee – Presentation of the Adapto project to local stakeholders.
• November 28, 2018: On-site meeting with the Prefect of Pas-de-Calais.
• December 21, 2018: Establishment of a monitoring committee for the northern bank of Authie Bay – DDTM (lead), CA2BM, DREAL Risks, DREAL Nature, Conservatoire du Littoral.
• January 22, 2019: Marine Park – envisioning coordination between Marine Educational Areas and the Adapto educational project.
• March 6, 2019: Feedback and site visit in Normandy (Communauté de Communes de Coutances Mer et Bocage).
• March 11, 2019: Discussions on the action program around the bay with local stakeholders.
• March 14, 2019: Technical committee for urgent works at Authie Bay – DDTM (lead), CA2BM, DREAL Risks, DREAL Nature, Conservatoire du Littoral.

Located between the municipalities of Bastia and Penta di Casinca in Haute-Corse, the Golo Delta site stretches along nearly 30 km of coastline. It is a low, sandy formation with a lido that encloses the Biguglia lagoon. Its low profile and substrate make this area vulnerable to various coastal hazards, particularly extreme marine weather events. The richness, uniqueness, and pressures affecting these areas have led the Conservatoire du littoral to undertake land acquisition efforts covering nearly half of the coastline.

Along this coastline, the natural areas and significant economic interests must be understood and managed to organize their coexistence through the development of intention frameworks for integrated coastal zone management.

In some parts of this coastline, the environments are neglected, and the dune ridges are heavily weakened by natural impacts (storms and swell) and human pressures (buildings close to the shoreline and uncontrolled motorized use of the beaches). On Conservatoire-owned land, protective measures such as the installation of sand fences help address the issues of uncontrolled beach use and allow the dune ridges to rebuild and stabilize, restoring their natural function as barriers against saltwater intrusion.

Moreover, the Golo Delta site hosts remarkable biodiversity, including, for example, the presence of large-fruited prickly juniper, Hermann’s tortoise, and the European pond terrapin at the Mucchiatana site—species that are emblematic and of major heritage interest. Beyond these species, the delta’s geological history has also created notable wetland and coastal habitats, which are now recognized and protected as the Biguglia lagoon nature reserve, ZNIEFF sites, and Natura 2000 zones.

A study conducted by BRGM, based on shoreline evolution from 1948 to 2007, revealed different trends in coastline change across the site: some areas show sand accumulation and shoreline advancement towards the sea, while others are eroding, with local erosion rates near the Golo river mouth reaching up to 100 meters over 50 years. Using this historical analysis, BRGM projected the shoreline’s future evolution up to 2050.

The Conservatoire is actively promoting the Adapto approach among public and private stakeholders in the region, including raising awareness about responsible beach cleaning and supporting sustainable development efforts that consider long-term challenges.

Project actions and outcomes

The areas of reflection that have guided the development of the project for this site are numerous but compartmentalized (hydro-sedimentary functioning, naturalist monitoring, landscape components, etc.). These should be integrated and enhanced through a more holistic understanding. Furthermore, the site deserves local support to monitor environmental changes where natural dynamics are now freer to operate.

Forward-looking scenarios, informed by economic factors, will serve as a basis for dialogue with local stakeholders in the eastern plain (elected officials, associations, professionals, residents, and government services).

These steps are essential conditions for establishing robust, shared solutions.

Additionally, the Conservatoire will continue its efforts to protect the coastal area through land acquisition, dune ridge restoration work, and facilities to welcome the public.

Chronology

September 2018: Meetings with economic stakeholders (hospitality sector) of the study sites with the BRLi office. The goal was to present the results of the proposed development scenarios, the cost-benefit analysis, and the multicriteria analysis.

October 2018: Information meetings with residents of housing estates located on the dune ridge in the communes of Biguglia and Borgo: presentation of a technical plan for the restoration and protection of the coastal area, gathering participants’ feedback, and responding to their questions. Read the report.

February and March 2019: Presentation of technical restoration and coastal protection plans to the town halls of Furiani and Castellar di Casinca.

Spring 2019: Development works carried out as part of the Adapto project in the communes of Borgo and Venzolasca.

With an area of 635 km², the Gironde estuary is the largest estuary in Western Europe. The alluvium carried by the Garonne and Dordogne rivers contributes to the formation of sandbanks (vasards) in the Gironde estuary: each year, between 1.5 and 3 million tons of suspended particles settle, forming banks that can develop into islands. The Mortagne-sur-Gironde polder and Île Nouvelle, formerly cereal-growing areas, were purchased by the Conservatoire du littoral after Storm Martin in 1999, when they were partly overtaken by the sea. The Conservatoire decided not to block the breaches on these lands but to let the tides act freely and to monitor the evolution of these environments.

Mortagne-sur-Gironde polders

On the north bank of the Gironde estuary, polders were created between 1960 and 1970 in the commune of Mortagne-sur-Gironde with the aim of establishing intensive agricultural production on estuarine salt meadows that were previously underutilized and regularly covered by brackish waters.

Storm Martin in 1999 created breaches in the embankment system of a polder located downstream of the port of Mortagne-sur-Gironde, and water flooded this area. To protect the homes, a new dike was then built further inland, closer to the former shoreline. The Conservatoire du Littoral acquired the parcels located within the former embanked zone, and since then, the Regional Conservatory of Natural Spaces (CREN) Poitou-Charentes has been managing these lands.

At this site, the sedimentation rates observed are remarkable: within ten years, the original topographic level was regained, and a gradual recolonization by vegetation typical of estuarine marshes began. Beyond the intrinsic qualities of these habitats, the reed beds act as a buffer by absorbing part of the energy of the incoming swell, which reduces its impact on the coastline.

Nouvelle island

L’Île Nouvelle first appears on maps in 1825 as two islands, Île Bouchaud and Île Sans-Pain, shaped by the meeting of sediments from the Garonne and Dordogne rivers and marine sands. The island appears as a single entity after 1866.

From the mid-19th century to the 1960s, Île Nouvelle was farmed for its lands enriched by the estuary’s silt. Initially a vineyard area, it escaped the phylloxera plague that devastated French vineyards at the end of the 19th century thanks to regular flooding of the river, which drowned the aphid responsible for the disease. Viticulture gave way to cereal farming in the 1960s. The island’s last farmer ceased activity in 1997.
It was for its remarkable ecological potential that the Conservatoire du Littoral purchased the island in 1991. Management was entrusted to the Gironde Department.

Two major climatic events influenced the Conservatoire’s and Department’s decisions on projects to undertake.
During Storm Martin in 1999, a breach opened in the dike of Île Sans Pain, causing significant flooding of that part of the island and the village, raising awareness about the nature of projects needed. From then on, a renaturation program involving the deliberate opening of a breach seemed possible. The manager and owner drew on Dutch experiences with marine reconnection to initiate this renaturation program. The island was twinned under the EUROSITE2 program with the Dutch island of Tiengemeten.

Storm Xynthia in 2010 created a new breach in the northeast dike of Île Bouchaud and accelerated the fully embraced objective from the beginning: “to let the island flood with river waters.” This northern part, directly connected to the river, is evolving rapidly: the island is losing its forest cover, a mudflat is forming and is gradually being replaced by a rich and welcoming reedbed.

In 2006, the Conservatoire launched a management plan to define the site’s long-term objectives. These can be summarized as renaturing this agricultural island through a “flexible” management of the coastline on the northern part (Bouchaud) and controlled water level management on the southern part of the island (Sans Pain). This management approach, started over 10 years ago, is restoring the original state of the estuarine marshes that existed before the “viticulture and agriculture period.” Flora and fauna quickly recolonize the areas, biodiversity returns.

Alongside the island’s renaturation, the Conservatoire and the Gironde Department wanted to preserve the memory of the people who lived and worked on the island by conserving and highlighting its built heritage. A large restoration program of the buildings on Île Sans Pain (the winery, the manager’s house, the school, and agricultural workers’ housing) and hydraulic structures was completed in 2016. To welcome the public (a key aspect of the project), a trail was created in the southern part with wooden decking and a hide.

The northern zone has continued to evolve freely since the 2010 storm, with a buffer enclosure protecting this “free evolution” area from the southern enclosure that receives visitors.
Île Nouvelle is a Protected Natural Area (Espace Naturel Sensible) managed by the Gironde Department, a true “open-air laboratory” for renaturation. It offers visitors a chance to discover estuarine marshes, their species, and the identity landscapes of the Gironde estuary. It preserves the memory of the past life of the “îlouts,” its former inhabitants. Finally, it serves as a showcase of the flexible coastal management approach engaged for nearly 10 years, symbolizing adaptation to climate change and a magnificent demonstration of the benefits nature offers us.

The northern part of the island (the former Île de Bouchaud) is closed to the public to ensure a peaceful space for the many bird species that frequent it.

Project actions and outcomes

The Gironde estuary is a valuable site for the Adapto project because this area benefits from comprehensive monitoring organized by the managers; the evolution of these territories will serve as a reference for other sites that are currently at earlier stages in the process. The Gironde estuary can thus contribute to the Adapto network of sites facing similar challenges.

The presence of the two experimental sites will also enable reflections on the future of other polders in the Gironde estuary under similar conditions, allowing local stakeholders to conduct prospective studies exploring multiple possible development scenarios.

The Adapto project will primarily implement detailed monitoring actions: birdlife, fish populations, crustaceans, habitat mapping, sedimentation analysis and modeling, social acceptance, ecosystem services, and landscape evolution.

This comprehensive data set will allow local stakeholders to understand and appreciate the ecosystem benefits provided by these natural spaces.

Nouvelle insland

The breach at high tide – July 2018

The breach at low tide – July 2018

The projects undertaken and the work carried out over the past ten years provide many answers about the services offered by marine reconnection: changes in vegetation cover, diversity of bird species, refuge and nursery areas for fish, etc.

The Adapto project will implement, in particular, two actions:

• The implementation of the IRSTEA research agreement (Institute for Research in Environmental Sciences and Agriculture) related to ecosystem services in order to establish an inventory of the benefits linked to estuarine reconnection (2018–2020).
• The implementation of the “ecological quality habitat indicators” method with the MNHN (National Museum of Natural History).
• Monitoring of the bathymetry of the breach and the channel by BRGM (Geological and Mining Research Bureau).
• A social perception study of the site’s stakeholders and users.

This set of data will enable local stakeholders to understand the ecosystem services provided by nature and the feasibility of flexible management on an estuarine island.

Chronology

Mortagne-sur-Gironde polders

• September 2018: Renewal of the photo campaign for the landscape observatory of the Mortagne-sur-Gironde polders – CREN + aerial photo campaign.

Ile Nouvelle

• March 26, 2018: Presentation of Adapto to the management committee bringing together elected officials of Gironde, the manager (Cd33), and the Conservatoire du littoral.
• May 30, 2018: The Adapto project is presented to DREAL Aquitaine.
• Summer 2018: 47 hectares of Public River Domain are assigned to the Conservatoire du littoral by the Grand Port Maritime de Bordeaux.
• Summer 2018: Screening of the film “Et demain, on fait quoi?” (“So tomorrow, what do we do?”) at a school in Pauillac. Organized by the Aquitaine Delegation in partnership with CPIE Médoc (Permanent Center for Environmental Initiatives), already very involved in its educational program on climate change and flexible management issues.
• September 13, 2018: Presentation of the Adapto project to the local steering committee (Copil) which includes managers, partners, State services, scientists, and users.
• November 2018: Signing of a partnership agreement with IRSTEA (2018-2020). Implementation of a research and development program to evaluate the services of estuarine reconnection by studying the trophic functioning of aquatic communities and the associated ecosystem services approach (economic/ecological component).
• January 17, 2019: Site management committee meeting including Cdl/Cd33 with elected officials from the department, presentation of scientific monitoring programs under the Adapto project.
• February 7, 2019: Conference in Sadirac (33), presentation of Adapto by the Aquitaine delegation on flexible coastal management actions for pilot sites in Aquitaine (Leyre Delta – Ile Nouvelle). Conference organized by the Terre et Océan Association. 40 participants.

The Lancieux Bay is an area gradually reclaimed from the sea by humans (polder). Over the centuries, the successive construction of dikes (such as the Dike of the Monks, the Roche Dike, or the Beaussais Dike) and irrigation canals has made it possible to develop agriculture.

The landscape has thus been shaped according to human needs, alternating between salt meadows, vegetable farming, bocage pastures, apple orchards, cereal crops, and wet meadows.

The Conservatoire du littoral’s land ownership of the polder has made it possible to initiate a transition of agricultural land. By establishing permanent grasslands without inputs, the aim is to improve water quality and reduce economic pressures in a sensitive area.

The Lancieux Bay has retained a wild character, with a great diversity of natural landscapes, while still being inhabited and used by humans.

Between the 13th and 16th centuries, the Benedictine monks of the Abbey of Saint-Jacut built a dike, now known as the “Dike of the Monks.” It enabled the draining of the coastal marshes for agricultural use. Later, the Roche Dike (18th century) marked the extension of the polder to its current boundaries. The Beaussais marshes (Ploubalay polder), separated from the Lancieux polder by a watercourse, were drained through the construction of a dike in the early 19th century. These two adjacent polders form a coherent unit within the Lancieux Bay.

The Dike of the Monks is the oldest heritage feature of the site and represents a valuable testimony to the development of the land-sea interface over past centuries.

Project actions and outcomes

Climate change and rising sea levels are causing changes along the coastline. During high spring tides, the sea now reaches the tops of the dikes and sometimes overflows them during storms.

Since 2015, new approaches to land management have been explored in order to anticipate the effects of rising sea levels. A strategy of planned dike retreat over time is gradually giving back to the sea what humans had reclaimed.

Accepting the maritime nature of the bay means shifting the perspective of users—allowing the sea to reclaim some space and creating new areas for walking and recreation.

Allowing saltwater to enter the low-lying inland marshes in a controlled way provides a new area for sea expansion. This helps absorb part of the sea’s energy during storms and reduces the cost of building and maintaining protective infrastructure. The bay offers favorable conditions for this flexible approach to coastal management.

Several reconnection scenarios have therefore been evaluated for the Lancieux polder:

• Dike removal
• Creation of breaches
• Installation of water control structures (sluices)
• Natural (uncontrolled) tidal flooding

Thus, in the municipality of Lancieux, this transitional area makes it possible to envision a layered protection system based on:

• The restored historic Dike of the Monks, repurposed as a walking path;
• A new, limited-length dike providing protection for people and property between the Dike of the Monks and the urbanized areas;
• The controlled intrusion of saltwater into the area returned to the sea, creating a new salt meadow marsh that helps dissipate wave energy.

The aim here is to balance heritage, environmental concerns, and the use of natural spaces through a strategy of gradually supporting the landward retreat of the coastline.

Chronology

• July 27, 2011: Resolution by the Lancieux municipal council proposing a system of successive defense layers: relying on the Dike of the Monks and, if necessary, implementing a third dike to protect the campsite and nearby homes.
• 2015: Hazard study – Assessment of the dike’s condition and maintenance recommendations. Definition of the vulnerable area.
• 2016: Meetings with mayors and intermunicipal officials – concerns about how residents might receive the project. Desire to highlight the benefits of the project for local residents as well as for tourism. Growing awareness of the emerging challenges related to climate change, which the Community of Municipalities will have to address within the GEMAPI framework (flood risk and aquatic environment management).
• November 4, 2016: Presentation of the results of geomorphological and landscape university studies to elected officials of the Côte d’Emeraude. Questions raised about project funding and the interest in a reconnection initiative rather than simply allowing nature to take its course. Desire to include cost estimates and assess technical and legal feasibility for each scenario.
• November 15, 2016: Exchange day between elected officials from Val de Saire (Licco site, Normandy) and those from the Bay of Lancieux on adapting coastal territories to climate change.
• 2017: Studies on “Ecosystem services of a Slikke-Schorre complex” and “Biogeomorphology and evaluation of the storm attenuation service of the Lancieux Bay salt marsh” (EPHE study).
• November 21, 2016: Discussions with the municipality of Lancieux on establishing a DUP (Public Utility Declaration) to secure land control—key to advancing the Adapto project.
• November 6, 2017: COPIL (steering committee) meeting for the implementation of GEMAPI.
• July 11, 2018: Site management committee for Tertre Corlieu and Beaussais Marshes.
• August 8, 2018: Meeting with the mayor of Lancieux about land acquisitions and water management in the Lancieux marsh.
• November 2018: Acquisition of parcel AH 238.

In French Guiana, large mudbanks move along the coastline from east to west. When present, they dissipate wave energy, protect the coasts from erosion, and allow mangroves to develop. When absent, waves break directly on the beaches, causing stronger erosion. In this way, the coasts of French Guiana are highly dynamic and ever-changing.

Until the early 1980s, the coastline of Mana was made up of a mosaic of wetlands and mangroves along the shore. This area, called the “Savane Sarcelles,” was then converted into a large 5,000-hectare polder dedicated to rice cultivation, which led to the creation of new open wetland habitats rich in biodiversity.

Between 2000 and 2016, in the absence of a protective mudbank, the coast receded by one and a half kilometers.

In addition to these erosion problems, other constraints and difficulties arose that hastened the end of the large rice development project on the site: regulatory changes, changes in ownership, and various economic challenges.

This agricultural decline led to the closure of wetland habitats, which became less rich in biodiversity.

The Mana polder is known for its remarkable and unique ornithological richness at the scale of French Guiana. Each year, it hosts hundreds of thousands of birds from over 200 different species. Among these, migratory shorebirds represent the largest populations, and for them, conserving the Mana polder’s carrying capacity is a conservation issue of global importance.

Aware of these stakes, the Conservatoire is undertaking land management actions to protect this area and preserve its richness by implementing a site project based on diversified agricultural use, public access, and ecotourism development focused on birdwatching.

Project actions and outcomes

The Adapto program plans to implement several studies, some of which are essential for developing the site’s management plan. An example is the BRGM study aimed at modeling the medium-term projection of the coastline. This study will help define the boundary between the natural area, where a flexible coastal management approach will be tested, and the exploited area, thereby establishing an appropriate management strategy.

Maintaining open habitats through cattle grazing, combined with the restoration of the hydraulic network, will contribute to preserving wetlands favorable to birdlife. The ornithological richness of the rice fields gives them strong ecotourism potential. Birdwatching could eventually become the main activity in the former rice fields.

Chronology

2018

• July 5: Land acquisition of 1,500 hectares.
• September 3: Acquisition of a pre-emption right on an area of 2,200 hectares.
• September 14: First steering committee for the development of the management plan; a consortium of four consulting firms is responsible for its implementation.
• October 17: BRGM begins a study aimed at modeling the medium-term (50 years) projection of the coastline and the risk of marine flooding on the polder.
• November 19: Start of the landscape study in partnership with ENSP.
• November 28: First technical committee meeting; BRGM explains the vulnerability of the rice fields to erosion and marine flooding.

2019

• March 11 to 16: EUCC-France workshop in Guyana. Meeting between researchers, managers, and elected officials to exchange knowledge and management strategies for the Guyanese coastline. The Adapto project and results of the landscape study will be presented.
• May 13 to 17: Study trip to Camargue; stakeholders from the Mana territory and elected officials visit sites facing similar issues to Savane Sarcelles.
• May: Results of the BRGM study, on which the consulting firms in charge of the management plan will rely to finalize their diagnosis.
  June: Second steering committee for the management plan; consulting firms will present the results of their diagnosis.
  Workshop on agriculture with actors from the agricultural sector and project leaders to discuss allocation conditions and individual needs.
• July: Start of work to create the first public access to the sea.
• September: Implementation of educational activities in Mana primary schools in partnership with the Association for the Discovery of Nature in Guyana (ADNG).
• December: Third steering committee meeting presenting the project definition for the site.

Located on the coastal fringe of the Brouage marshes, between the Marennes peninsula to the south and the Moëze hills to the north, the Moëze marsh was gradually formed over time by the progressive silting of the Gulf of Saintonge by the alluvium from the Charente River. Slowly transformed by humans into salt marshes through digging and embankment, today’s marsh retains this heritage in its typical landscape of raised mounds (bossis) and canals.

After the gradual abandonment of the salt pans, the former saline plots in the heart of the marsh gradually silted up and were converted from the 19th century onward into hay meadows and pastures for extensive livestock grazing, while some areas along the coastal zone were re-dug and reused for oyster farming. More recently, parts of the marsh have been drained to allow cereal cultivation.

This site includes a wide range of wetlands that support the establishment and development of remarkable biodiversity. Located right in the heart of a migratory route and featuring suitable habitats, the site is of major importance for the wintering, refuge, and migration of many waterbirds and has been partly occupied since 1985 by the Moëze-Oléron National Nature Reserve.

On this vast marsh, rich in historical, natural, and human heritage, the coastal dike is weakened by recurring climatic hazards. Several management and coastline evolution scenarios need to be studied to determine the future of the site.

Project actions and outcomes

The earthen dike located along the seaside at the Moëze site is repeatedly battered by waves and swell, causing frequent maintenance issues. The scarcity of materials needed for these works makes it increasingly difficult to keep this structure in good condition. Further north, a dune ridge weakened by erosion provides coastal defense. In this context, the Conservatoire aims to support the site’s evolution through a collaborative and shared approach.

To this end, various coastline management scenarios will be studied and analyzed based on local concerns related to landscape, biodiversity, economy, and social perception. This will provide elements for reflection, support for consultation, and aid in decision-making.

Chronology

• 2016: Conducted a historical and landscape diagnosis of the Brouage marsh – ENSP.
• March 2017: Presentation of the landscape diagnosis at the Marshes Forum.
• March to August 2017: Agricultural diagnosis carried out – Cdl / CA17.
• August 2017: Presentation of the agricultural diagnosis to the marsh farmers.
• October: Signing of Life Adapto.
• January 2018: Launch of BRGM study modeling different coastline management scenarios.
• May 2018: Technical committee – presentation of the development of the BRGM hydrodynamic model.
• September: Technical committee – presentation of the first BRGM modeling results.
• February 2019: Committee of mayors of the Brouage Marshes Agreement – presentation of the first coastline management scenarios.

The morphology of the Orne estuary, from Caen to the sea, was significantly altered following the construction of the canal in 1857. After passing through Caen, the Orne River splits into two straight lines that structure the surrounding landscape. These two watercourses—the Orne and the canal—flow between two agricultural and urban plateaus, shaping a variety of evolving landscapes. The western corridor, guided by the canal, conveys an industrial and port-related character. To the east, the river changes with the tides, feeding a rich natural heritage: the Bay of the Orne.

The river’s embankment led to the disappearance of salt marshes (schorre) over much of the site. The banks of the Orne were reclaimed (polderized) all the way to its mouth. The Cagny marsh dike was built in the 18th century, transforming the former meander and its salt meadows into grazed wet grasslands. The François Fields polder is the result of more recent embankment works (1960s) on a tidal flat. As a result, downstream from the Montalivet dam (in Caen), the lateral expansion zone for natural habitats and tidal flooding now remains along only about one-fifth of the river’s length.

In 2011, the Cagny marsh dike failed, causing flooding in low-lying areas. During high spring tides, the sea occasionally overtops the dike, forcing the temporary closure of the cycle path built along its crest. This calls for a reassessment of the dike’s future—and more broadly, of the land behind it.

Today, available data on this site indicate that maintaining these polders in their current state is not the only possible vision for the future of the area. In fact, the return of salt meadow vegetation in the François Fields sector offers clear benefits in terms of economy, biodiversity, and landscape.

On the Cagny marshes, the LiCCo program (Coastal and Climate Change), carried out from 2011 to 2014, provided valuable insight into the evolution of the Orne estuary. A collective reflection was launched with all local stakeholders on what the coastline of tomorrow could look like. Adapting this estuary in the context of climate change and rising sea levels is based on:

• A vision for 2050: the development of a larger, deeper estuarine area to increase climate resilience;
• A trajectory to 2025: implementation of concrete, localized projects to re-establish lateral floodplain connectivity and promote coastal mobility.

The Orne, heavily canalized, lacks sufficient space for flood expansion—raising the issue of opening up the polders and affected marshes.

Project actions and outcomes

At Sallenelles, the approach involves working with local stakeholders to define public access facilities during the re-flooding of the François Fields.

Regarding the Cagny marsh, a process of reflection and project definition needs to be initiated, starting with historical and landscape analyses, followed by the development of prospective scenarios. In a scenario involving sea level rise, erosion, and rising groundwater levels, the current Cagny marsh dike would become obsolete and lose its protective function. Based on this analysis, the Conservatoire du Littoral and the Calvados Departmental Council, which manages the natural areas, are working on an alternative to the existing cycle path.

If the maritime character of the marsh is restored, new walking, cycling, and boating routes would offer visitors new experiences. Starting from the Nature and Estuary House, these paths contribute to maintaining the site’s appeal at the heart of the bay. At the same time, a consultation process should be conducted with Normandie Cabourg Pays d’Auge, the Chamber of Agriculture, Safer, the Conservatoire du Littoral, and local farmers to plan the gradual adaptation of their working tools over the coming years for this scenario.

Preliminary Study for 2050: Download now

Furthermore, addressing climate change requires a broader perspective than just the mouth of the Orne estuary (the intervention area of the Conservatoire du Littoral). Restoring the maritime character of the Orne demands a well-considered strategy at the scale of the entire Orne River—from Caen to the sea. Planning adaptation through different stages up to 2050 involves the participation of various stakeholders:

• The Calvados Department (greenways, sensitive natural areas, etc.), the CPIE
• The City of Caen, the Communauté de commune Caen la Mer, the Communauté de commune Normandie Cabourg Pays d’Auge, and the municipalities located downstream of the estuary (GEMAPI, urban planning documents, urban development of the peninsula…)
• Ports of Normandy (master plan for port development)
• State services (Risk Prevention Plan).

A lido is a sandy coastal barrier that encloses a lagoon. The lido of Petit and Grand Travers, also called the lido de l’Or, separates the Étang de l’Or from the Mediterranean Sea, divides two highly urbanized areas (Carnon and La Grande Motte), but offers a succession of dune ridges, salt marshes, and forested areas of great ecological, landscape, and cultural value.
It is largely owned by the Conservatoire du littoral, which has been managing this site since 1976.

The Petit and Grand Travers lido site is part of a larger sedimentary unit (the Bay of Aigues Mortes), which is subject to ongoing erosion.
In 2008, the Hérault department carried out emergency works across this entire bay, where beaches and dune ridges were at risk of no longer fulfilling their role as a natural barrier against marine incursions. A large-scale replenishment operation was undertaken: one million cubic meters of sediment brought by the Rhône River were extracted and then deposited on four areas of the Bay of Aigues Mortes (with an estimated benefit of between 300,000 and 400,000 m³ for the Lido de l’Or).

The sustainable development program for the lido, studied and coordinated over ten years, resulted in 2015 in the renaturation of the dune and a complete reorganization of visitor facilities on the site. The key feature of this operation was the removal of a section of the road built on the dune, which allowed natural dynamics to resume.

Download the file (Rehabilitation of the Petit and Grand Travers Lido – Public presentation of the project 2014).

Petit Travers before work

Petit Travers after work

Project actions and outcomes

Among the range of approaches within the Adapto project, the Petit and Grand Travers site is one of the most advanced. The large-scale works carried out from 2003 to 2015 are the result of a shared commitment between the Conservatoire and its partners (the Hérault Department, the municipalities of Mauguio-Carnon and La Grande Motte, and the Pays de l’Or Agglomération).

This site will therefore provide valuable feedback for other sites within the network. A site narrative will help preserve the memory of the site’s history and organize a handover between different generations of stakeholders, building on the extensive consultation work that has been done. Furthermore, the site deserves ongoing local support to continue this dynamic of cooperation, maintaining its role as a pilot and innovative site in terms of flexible coastal management.

The project also plans to monitor the evolution of the environment under the influence of more flexible and spontaneous natural dynamics, as well as track users’ perceptions of the site in the context of using and appropriating a project of this kind. Finally, a forward-looking study will evaluate the relevance of different development scenarios for the Grand Travers, incorporating economic, biodiversity, landscape, environmental, societal, legal-economic, and administrative aspects.

Chronology

• December 2018: Adapto day in Occitanie, raising awareness among elected officials about a site developed for climate change adaptation: Le Petit et Grand Travers.
• 20 elected representatives from different areas attended and shared their experiences gained at Petit et Grand Travers.
• February 2019: Work by students from the Master’s program in Coastal and Marine Management at the University of Montpellier: collection of historical data generated during the consultation on the redevelopment project of the Lido de l’Or.
• May 2019: Aerial photo campaign using a kite.

Until the end of the 18th century, the Arcachon Basin consisted of extensive salt meadows, which were diked by large private landowners for productive purposes.

The Domaine de Certes et de Graveyron and the Île de Malprat, sites managed by the Conservatoire du Littoral in the heart of the Arcachon Basin, are influenced more or less directly by the Leyre Delta and provide a natural window into an urbanized area. These three sites are strongly linked to the territory’s identity, and the local population is very attached to them.

For both the Domaine de Graveyron and the Île de Malprat, the breaches observed in the dike system have been allowed to evolve naturally. The hydraulic compartments regularly flooded by the sea have changed configuration, transitioning into salt meadow areas.
After about twenty years, it is observed that the opening of the Graveyron breach has stabilized at a width of approximately 20 meters. Around this breach, the dike has transformed into a berm that has lowered and widened but has not completely disappeared.
Inside the hydraulic compartment, a salt meadow has established itself and has gradually elevated over time. This area now helps absorb wave energy through its structural characteristics (surface area, roughness, and absorption by salt meadow vegetation) and its altimetric profile.

Project actions and outcomes

Benefiting from flexible coastal management since 1996, the Leyre Delta site is an advanced location.

Numerous studies support the area, notably the multidisciplinary research program Liteau Barcasub from 2010 to 2013, which resulted in the proposal of several possible evolution scenarios for the diked areas of the Delta.

Adapto will build on the experience gained from sectors partially reconnected to the sea, which benefit from a large amount of data collected over the past 15 years.

The Adapto project at this pilot site will primarily focus on highlighting this data to share it with the public through the creation of educational tools and programs.

The landscape approach, to be developed in cooperation with the Council of Architecture, Urbanism, and Environment 33, will be a valuable tool, as will the historical analysis.

Chronology

• October 11, 2017: Spanish managers of the European Franco-Spanish cooperation project Txinbadia+ visit the Leyre Delta site.
• 2018: Photographic monitoring campaign, the results of which will be compared to those from 2007.
• May 30, 2018: The Adapto project is presented to DREAL Aquitaine, to the Sea and Coast service of DDTM33 in October, at the Rivages Council, and at the Coastal Dynamics Workshop of the Ministry in Capbreton.
• March 26, 2018: The Adapto project is presented to the management committee bringing together Gironde elected officials, the manager (Cd33), and the Conservatoire.
• October 2018: Meeting of Aquitaine Coast Guards on the theme of climate change adaptation, with the participation of Hervé Le Treut, Cyril Mallet from the Aquitaine Coast Observatory, the Director of GIP Littoral Aquitaine, the South Atlantic Botanical Conservatory, and Caue 33. Presentation of the Adapto project and the pilot site of the Delta.
• January 17, 2019: Presentation of the Adapto project to the management committee of the Domaine de Certes and Graveyron, involving Cdl and CD33, in the presence of departmental elected officials.
• February 7, 2019: Conference at the Aquaforum of the Terre et Océan Association in Bègles (33), presentation by the Aquitaine delegation of flexible coastal management actions and the Adapto project for pilot sites in Aquitaine (Leyre Delta – Ile Nouvelle).

The Vieux Salins d’Hyères site was acquired by the Conservatoire du Littoral in 2001. The protected area covers 365 hectares, making it a major protected natural space in the Hyères harbor. Along with the Salin des Pesquiers, it bears witness to the former salt production activity that was a cornerstone of the local development of the Hyères harbor. The site’s governance is managed by the Conservatoire and its partners (the Toulon-Provence-Méditerranée Agglomeration Community (TPM), the municipality of Hyères, and the Port-Cros National Park).

The current management plan organizes hydraulic management of the site similar to the former functioning of the salt marshes, with the aim of optimizing ecological and ornithological quality. However, this configuration is challenged by several phenomena, notably erosion of the dune ridge to the south: coastline retreat, loss of Aleppo pines and shaded areas, beach scouring, and threats to the site’s hydraulic structures.

The rock armor present on part of the site limits erosion where it is installed but directly amplifies it downstream of the sediment transport, disrupting the hydro-sedimentary functioning at the bay scale.

Studies conducted by BRGM and Aix-Marseille University have shown that this coastal wetland is a favorable site for implementing adaptive management actions for the coastline and natural areas, such as the removal of rock armor from the coastline with a view to renaturation.

Following an initial phase of rock removal over 100 meters at the western end of the structure, the manager TPM launched a study in 2017 (Artelia) to define a management strategy for the coastal ridge. This study explores the following options:

• A protection scenario (hard protection with dikes, etc.),
• A scenario to accompany the site’s evolution according to hazards,
• A renaturation scenario with natural rebalancing of the coastline,
• A no-action scenario.

The steering committee ultimately decided to combine two scenarios: “renaturation of the coastline” and “accompanying the site’s evolution through ecological engineering operations.”

The works and the project for this site are part of two European projects: Marittimo (Franco-Italian Interreg 2017–2019) and adapto (2017–2021).

Project actions and outcomes

The overall project aims to restore a natural dynamic to the dune-beach system that forms the interface between the sea and the wetland. To achieve this, the plan is to remove the rock armor and then gradually adjust the facilities and public access according to the environment’s evolution.

The adapto actions will focus on organizing the follow-up to the major works carried out under the Marittimo project (removal of the rock armor).

This will include ensuring continuity of the coastal promenade during bad weather by creating an alternative path and monitoring the evolution of the lagoon ecosystem, including the Posidonia seagrass beds that fringe the beach.

More generally, the project will develop actions directed towards users, the local population, and elected officials to address their concerns and prepare future changes together.

Chronology

• February 2019: Contract awarded for the construction of the pedestrian path and for the rehabilitation of the dune cordon and rock removal.
• April 2019: Start of the works; presentation of the exhibition on the project created as part of the educational activity by CPIE Côte Provençale and site visit with around thirty participants.
• July 2019: Completion of the construction of the path and restoration of the dune cordon.
• September 2019: Contract awarded for the monitoring of seagrass beds and start of the study.
• October 2019: Completion of rock removal works over 340 meters of coastline.
• April 2020: Second monitoring campaign of the seagrass beds.
• August and October 2020: Social perception surveys conducted among site users.
• October 2020: Extension of rock removal over an additional 275 meters. The Vieux Salins coastline has thus been renatured over more than 600 meters.
• September 2020: Third monitoring campaign of the seagrass beds.
• November 2020: Field trips for 4 classes from Hyères primary schools: discovery of the Vieux Salins and land art workshop on the theme of natural and artificial evolution of the coastline.
• September 2021: Fourth monitoring campaign of the seagrass beds.