Leyre delta

Gironde (33)

Until the end of the 18th century, the Arcachon Bay was made up of important salt meadows dyked by rich landowners for a productive purpose.

The Certes and Graveyron Domain and the Malprat Island, sites of the Conservatoire du littoral in the heart of the Arcachon Bay, are under more or less direct influence of the Leyre Delta and offer a natural area in an urbanized region. These three sites are strongly associated with the local identity, and inhabitants are very attached to it.

The breaches found in the dykes of the Graveyron Domain and the Malprat Island were left open to evolution. The basins regularly flooded by the sea have evolved and become salt meadows.

After 20 years, the Graveyron breach has stabilized at a width of about 20 meters. In the vicinity of this breach, the dyke has become a bump that has lowered and widened but has not completely disappeared.

Inside the basin, a salt meadow has appeared and has continuously risen: this space now contributes to absorbing the energy of the waves by its structural characteristics (surface, roughness and salt meadow vegetation absorption) and its altimetry profile.

The adapto project for the site

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

Numerous studies have accompanied the research on the site, including the interdisciplinary applied research program Liteau Barcasub from 2010 to 2013, which resulted in the proposal of several possible evolution scenarios for the dyked areas of the delta.

The adapto project will take advantage of return on experience on sectors partially reconnected to the sea, which benefit from a very large amount of data collected over the past 15 years.

The adapto project on this pilot site will make it possible highlight this data, in order to relay them to the public by the creation of educational tools and programs.

The landscape approach that will be carried out in cooperation with the Counsel in Architecture, Urban Planning and Environment (CAUE) of Gironde will be a valuable tool, like the historical analysis.

Site chronicle: the Adapto project

11th October 2017: The Spanish managers of the European Txinbadia + cooperation project visited the Leyre Delta site.

2018: Photographic monitoring campaign which results will be compared to those of 2007.

30th May 2018: The Adapto project is presented to the DREAL Aquitaine, the Sea and Coastal service of the Directorate of Territories and the Sea (DDTM) of the Département Gironde, in Coastline Council, and in the Coastal Dynamics workshop of the Ministry for Environment in Capbreton.

26th March 2018: The adapto project is presented to the management committee composed of the elected officials of the Département of Gironde, the manager (Département of Gironde) and the Conservatoire du littoral.

October 2018: Meeting of the Coastal Guards of Aquitaine on the theme of the adaptation to climate change, with the participation of Hervé Le Treut, Cyril Mallet of the Observatory of the Aquitaine Coast, the Director of the GIP Littoral Aquitain, the South Atlantic Botanical Conservatory and the CAUE of Gironde. Presentation of the adapto project and of the delta pilot site.

17th January 2019: Presentation of the adapto project to the management committee of the Certes and Graveyron Domain composed of the Conservatoire du littoral and the Département Council of Gironde in the presence of the elected officials of the Département.

7th February 2019: Conference at the Aquaforum of the organization Terre et Océan in Bègles (33):  presentation by the Aquitaine Delegation of the adaptive coastal management actions of the coastline and the adapto project of the pilot sites in Aquitaine (Leyre Delta - Ile Nouvelle).


1984 Purchase of the Certes Domain by the Conservatoire du littoral.

The Département of Gironde becomes manager of the Certes Domain.


Opening of a breach at the edge of the Graveyron site.

1998 Purchase of the Graveyron Domain by the Conservatoire du littoral.

Purchase of the Malprat Island by the Conservatoire with breaches in the sea dyke.
During its visit in the Delta, the scientific council recommends not to prevent the natural process of dyke erosion and to promote the regeneration of the salt marsh.

2003 Case study of the climate change impacts in Graveyron.

A survey of social perception reveals that the inhabitants do not understand why the maintenance of dykes has stopped.

2005 Construction of a backup dyke on Malprat Island
2007 Photographic monitoring.
2010 to 2013

Interdisciplinary applied research program Liteau Barcasub on the adaptation to the impacts of submersion.

2015 The national evaluation of economic benefits estimated the benefits of sea reconnections to €675,000 per year.
2017 Launch of the adapto project.

Pas de billet posté.

Leyre delta in pictures

Leyre delta in pictures

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