Restoration of Branugues stream – Batitan weir removal, France

Introduction

The Batitan Dam in Laroquebrou, Cantal, hinders the ecological flow of the Branugues stream, a key tributary of the Cère River. The Cère River originates in Massif Central’s mountains, with its Lot department valley designated as a Natura 2000 site, housing valuable heritage species like brown trout, otter, and brook lamprey, along with critical habitats such as alluvial forests, streams, trout areas, riverbeds, mines, and underground passages. This stream is the last potentially accessible tributary before the Nepès hydroelectric dam. Laroquebrou holds crucial spawning grounds for trout and brook lamprey, leading the Cantal Fishing Federation to view Branugues as a potential nursery stream. Their prior restoration efforts prioritise removing the Batitan mill dam to enable fish passage. However, precautions must be taken due to a house near the upstream dam.

Project context and opportunity

The SMDMCA is currently in the diagnostic phase of the multi-annual management plan for the downstream Cère basin, and discussions with technical partners, including The Cantal Fishing Federation, have prompted an evaluation of the Batitan dam at Laroquebrou. Over years, the Federation undertook bank protection, riparian restoration, and the removal of an unused dam on the Branugues stream, aligning with the SMDMCA’s ecological continuity efforts. Given the shared interest, ERN and the SMDMCA proposed this project within the Open Rivers Programme, leveraging funding to address the Batitan mill dam. Notably, this dam is marked in the flow reference system as impassable for a significant fish category and it detrimentally affects biodiversity upstream with excessive sand and sediment.

Project aims

The project’s primary goal is to restore ecological and sedimentary continuity by safely removing the dam without compromising the adjacent house’s foundation. This removal will open over 8 kilometers of waterway, relieving pressure on the Cère at Laroquebrou, granting access to 87% of the Branugues stream and enhancing grain size, water quality, habitats, and spawning grounds while improving the overall river hydromorphology.

The dam removal will enhance hydromorphology by preventing riverbed clogging from dam-retained sediments. Long-term aspirations include increased trout recruitment and population growth. The SDAGE 2022-2027 outlines moderate continuity and high morphology alteration pressures in the Branugues catchment area. This project aims to mitigate these pressures, resulting in positive outcomes for the sector.

Project achievements

Led by ERN (European Rivers Network), this project has made significant progress in addressing ecological continuity and preparing for the full restoration of the Branuges stream. ERN worked closely with the SMDMCA, the design office Hydrétudes, and the dam owner to identify and evaluate three potential removal scenarios. Following a thorough study of the dam’s impact on ecological continuity, a final removal scenario was selected, which involves removing the weir and introducing riprap in periodic rows to stabilise the banks. Streambed reprofiling enhances ecological continuity and ensures the structural stability of nearby buildings, particularly the old mill. This option also ensures the restoration of ecological continuity for aquatic species inhabiting the Branuges stream.

This project represents a step ahead in restoring the ecological integrity of the Branuges stream while addressing community and structural concerns. Through collaboration and thoughtful planning, ERN has set the foundation for successful dam removal and revitalisation of the watercourse.

The project was completed in January 2025 and received a follow-on demolition grant from the programme.