Context

Understanding the mechanisms of river restoration

The main aim of the Sélune restoration project, carried out by the French government and EDF, is to restore the river's ecological continuity. It is also intended to serve as an example for future river restoration projects. In fact, this project is unprecedented in Europe in terms of: the height of the dams (16 and 36 m) and the length of the watercourse flooded and belonging to the public domain (19 km).

Dam removal is the most drastic and effective solution for restoring the ecological continuity of watercourses. However, removing structures can also cause ecological disruption, the impact of which is difficult to predict on the environment. Cases of restoration through complete removal of the structures are relatively rare, and knowledge of the mechanisms involved in restoring watercourses remains limited.

The need for a multidisciplinary scientific monitoring

In order to assess the success of such operations in terms of restoration, a thorough scientific monitoring is necessary. There is a growing international momentum on this issue (see the AMBER project website and recent publications by Duarte et al. in 2021 and Habel et al. in 2020). The United States has pursued the most active dam removal policy to date. However, only a small percentage of these operations have been subject to scientific monitoring, and the majority of these have involved the removal of small dams (<15 m) (see the study by Bellmore et al. in 2017 and Habel et al. in 2020). In France, dam removal has not, to date, been properly documented scientifically, although three large dams were removed between 1996 and 1998 in Brittany on the Léguer and in the Loire basin.

Around the world, only a few restoration projects are monitored scientifically. Still, too few of them take into account the assessment the initial state of the system. Most monitoring focuses on the removal and restoration phases. However, knowledge of the initial state is essential for understanding the induced by the restoration operation. Furthermore, most of the scientific monitoring carried out focuses on a single aspect of the restoration, whether biological, morphological, landscape or societal (To find out more, see our booklet on the Sélune (in French only), published in 2021).

The aim of the Selune scientific program is to fill these gaps, by offering a comprehensive, multidisciplinary monitoring of the various phases of the restoration operation.