Habia Culvert, France

Introduction

The Arberoue River is a small river (3 metres wide) that provides habitat for trout and native white-clawed crayfish. The project focuses on an old culvert that has created a barrier for fish and crayfish. This area is important for our department as it still supports a population of native crayfish (Austropotamobius pallipes). This project will enable them to access refuge areas further upstream in the watershed. This sector was identified in the departmental plan to conserve this species in 2021.

The project consists of:

• Removing the dam with a mechanical excavator,
• Installing a footbridge (anchored only on the banks, without disturbing the riverbed).

Project context and opportunity

This project is part of an ambitious initiative to protect and restore small local streams. The project team collaborated with the landowner, a cattle farmer, who has been working since 2022 on:

• Installing fences around all meadows to prevent trampling by cows, with remote watering troughs installed;
• Planting hedgerows to reduce soil and nutrient erosion into the river.

Project aims

The barrier removal will reopen 800 metres of the main river upstream and 1.3 km of tributaries (a total of 2.1 km). The upstream area is currently not colonised by crayfish. Downstream, the next barrier (known as “Moulin du Château”) is located 6.5 km away, and this entire stretch is colonised by crayfish. In the context of crayfish and trout conservation, these small streams are as important as the main river.

The expected results are to:

• Restore upstream access for trout;
• Improve connectivity between the native crayfish population and other populations in nearby tributaries.

Project achievements

All preparatory tasks for the project have been completed, including comprehensive field measurements to assess the dam dimensions and estimated volume, consultations to secure the best quality and price for the work, and obtaining final authorisation for the project, which was granted in June 2023.

The removal of the old culvert and restoration of the riverbed began on 24 October and continued through 25 October. Following a temporary pause due to rain, the work resumed and was completed between 9 and 10 November, including the installation of a footbridge and the restoration of riverbanks.

The project has restored 2.1 km of the river for native trout and crayfish, significantly improving habitat connectivity and access. Additionally, the upstream accumulation of fine silt has cleared, enhancing fish habitat in the restored area.