Four weir removals on the Tardoire, France

The removals will significantly improve the morphology and natural functionality of the Tardoire, improving aquatic habitats for important fish species.

Introduction

The Tardoire River, from its source in the commune of Châlus to the brook of Suchés, has a total length of 114 km and drains a catchment area of 1200 km². It flows on a crystalline base up to Montbron and then on limestone soil, losing part of its water in the karsts. The Tardoire water is classified as having a medium ecological status with a good status objective for 2027.

The alteration of the hydromorphology of the Tardoire and the disruption of ecological continuity have been targeted as degrading factors of the ecological status of the aquatic environment. To achieve the objectives of good status and support the owners, the SYMBA Bandiat-Tardoire has carried out a global study to restore ecological continuity on 13 structures of the Tardoire from 2017 to 2020.

The SYMBA Bandiat-Tardoire has taken on the role of the project manager to restore ecological continuity by removing four structures on the Tardoire. These structures were selected because they have the greatest impact on ecological continuity and the quality of the environment.

At a glance

Project typeDam removal (demolition)
Project statusComplete
Removal dateDecember 2022 - July 2023
CountryFrance
RiverTardoire
Km opened24
Target speciesEuropean eel, brown trout
Websitesyndicat-bandiat-tardoire.fr/

Project context and opportunity

Other actions have been and are being carried out by the syndicate, such as the restoration of wetlands, the removal of water bodies, etc., which also contribute to achieving good water status. The future watercourse management programme will tend towards similar actions with the common objective of good water status.

The removals will significantly improve the morphology and natural functionality of the Tardoire. As a result, it will improve aquatic habitats, which will be more diversified and oxygenated, and water quality by acting on parameters such as temperature and the dilution factor.

Project aims

The project will also allow the free migration of fish species in the river. The target species identified are European eel and brown trout.

Removing these structures freed up a significant 24 km of the watercourse, in conjunction with removing the weir directly downstream carried out in 2017 (Puybonland mill), and also allowed reconnection with the tributary La Colle (over 3.20 km).

Overall, the ecological status of two bodies of water, “La Tardoire from the confluence of the Colle to the confluence of the Bonnettes” and “Ruisseau de la Colle”, will be improved, as well as the ZNIEFF.

ERN project website

Project achievements

Work to remove the four weirs has been successfully completed.

  • Les Planches : Removed from December 9 2022 to January 11 2023
  • Raux : Removed from february 14 to february 28 2023
  • Buisson : Removed from May 16 to June 14 2023
  • Peyrassoulat : Removed from June 16 to July 04 2023

This project showcased the river’s remarkable resilience to change, swiftly transforming zones of hydraulic influence and eddies into diversified flow fascias. The outcome was a substantial improvement in the granulometric distribution along the entire river length, addressing prior issues of silt and sand accumulation that hindered the river’s development and biological balance. Ongoing post-project monitoring includes hydromorphological monitoring, fish monitoring using electric fishing, and macrobenthic population monitoring for four years. The project on the Tardoire River successfully reopened over 20 km of the river, with future actions planned for nine priority weirs on the same river.



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