Scientific studies started in 2012. An agreement between INRA, AESN, AFB, FNPF, the French government and EDF secures the project until 2027. They are organized in three thematic areas:
– territorial dynamics and trajectories
– fluvial dynamics and water quality
– biocenosis, their functioning and evolution
Territorial dynamics and trajectories
Main interrogations: How do inhabitants, valley, river and lakes’ users see this ecological restoration project of the Sélune? What are the decisive criteria for its success? What changes to expect for agriculture and landscapes?
Landscape evolution is monitored through a photographic landscape observatory since 2013. It gathers 90 observation points scattered across the basin, photographed each season. The “Syndicat mixte du basin de la Sélune” (Mixed union of the Sélune basin) is a partner in these efforts.
On a wider scale, remote sensing (satellite imagery, drone and Lidar images) monitors landscape s’ evolution since the 50s. Investigations on agricultural practices complete the analysis to understand bonds between agriculture and landscape in the Sélune valley.
Uses and actors’ representations of this territory were also studied. Inhabitants and users’ opinions were analyzed to characterize their expectations and concerns with regards to the river valley.
Finally, the debate issued from the dismantlement governance project, as soon as it was announced, was analyzed. This work identified blockages, interruptions and struggles that underwent during this dialogue. The conflicts observed in the case of the Sélune was compared with those observed in other dam removal projects in the eastern US. Success or failure factors of such operations are therefore enlighten.
For more information: https://selune.hypotheses.org/
Fluvial dynamics and water quality
Dams are physical barriers to water flow, sediments transport and water chemistry. It is therefore necessary to have a good knowledge of these flows to understand changes associated to dams’ removal.
In particular, flow’s origin must be identified and its intensity measured in order to better interpret transfer processes, the role of hydrodynamic conditions and seasonal or exceptional (floods) variability. Water flow, turbidity and element contents are monitored thanks to automatic sensors spread up and downstream of the Sélune’s dams.
Finally, consequences on shape and stability of the riverbed are also part of the main interrogations following dams’ removal. Geomorphological dynamics and sediments transport are mainly followed through LIDAR imagery and electronic tracing (PIT-tag) of coarse elements.
These parameters are subject to a very close follow-up within the Sélune laboratory.
Biocenosis, functioning and evolution
The purpose is to understand biological processes in ecosystems restoration following dams’ removal. Aquatic photosynthetic organisms (phytoplankton, biofilm and macrophytes), aquatic macro-invertebrate (including crayfish), diadromous fishes migrating between rivers and ocean, and riparian vegetation are particularly scrutinized.
The spatial (up- and downstream of the dams, rivers and riverbanks) and temporal recolonization dynamics are subject to thorough monitoring within the Sélune Observatory.
The return of migrating species in the Sélune (salmo – Salmo salar, marine lampreys – Petromyzon marinus and fluviatile lampreys – Lampetra fluviatilis, shad Alosa sp. and eels Anguilla anguilla) will be spectacular. Risks of invasive species spreading (such as crayfish Pacifastacus leniusculus) is also a key issue. Their distribution are monitored through electric fishing, trapping, environmental DNA, acoustic video cameras and radio tracking.
Finally, relationships between the different living compartments, from microorganisms to fishes, are also studied. The objective is to identify mechanisms that are more complex and that involve the reorganization of ecologic communities, aquatic or riparian, after destruction of the dams.