Mise à jour le 13 January 2022

Hydromorphological restoration of the Gué Chatenay water body

Actions on watersheds

Background

In Vendée, numerous past works aiming to regulate the streamflow regime of watercourses have been created (recalibration, creation of works and lakes on watercourses etc.). These multiple works are  today  affecting the status of the water bodies. Only 2% of the water bodies in Vendée  have a  good status. Oxygen and the French fish resource river quality index for almost 80% of them were the features having led to the downgrading. The Gué Chatenay water body and its tributaries are at the crossroads of many challenges related to water quality and the preservation of aquatic environments: drinking water production, shellfish production… It is however classified as having poor ecological status.

Before the LIFE REVERS’EAU project, a diagnosis of the hydromorphological status of watercourses in the river basin headwater and of the impact of lakes on the Gué Chatenay water body was carried out. Further to the diagnosis, an intervention strategy was approved in consultation with the stakeholders in the area, to move towards good status through the restoration of degraded strips of watercourse and reduction of the impact of lakes, especially by disconnecting those draining the largest surface areas.

Schedule & Location

1st quarter 2021 / 4th quarter 2026

The action covers the Gué Chatenay water body.

Objective

The action aims to move towards good status and to reduce the impact of lakes, especially by disconnecting those draining the largest surface areas. The main challenges are:

  • To condense action to restore watercourses over the entire hydrographic linear surface, including the small stream system,
  • To improve water flow conditions especially by reducing the impact of lakes and restoring small stream systems,
  • To improve knowledge of the cumulative impact of lakes on watercourses,
  • To communicate about actions to restore watercourses to their natural state and to minimise the impact of lakes in river basin headwaters.

Description of the action

This action is presented in several sections:

1- Lake impact analysis

The impact of lakes and morphological restoration of small stream systems will be monitored (river basin fitted with measurement devices, water quality analysis etc.). A zero state will therefore be carried out in 2021.

2- Work implementation

All owners will be contacted to share the diagnosis and to suggest developments in favour of  good environment status. Therefore, lake bypass and removal  work will be carried out, along with diversification of water flows, remeandering, restoration of the watercourse profile by reloading with aggregates, resetting in the thalweg, removal of man-made structures in view of restoring continuity.

3- Furthering and dissemination of knowledge

A guide to reducing morphological, hydrological and pesticide risks in river basin headwaters in  Vendée  will be produced.

Main results expected

Removal/bypass of at least 6 lakes to reduce their impact

Return of at least 4 km of watercourses to their natural state (small stream system)

Creation of a guide to reducing morphological, hydrological and pesticide risks in river basin headwaters in Vendée

All river basin actions
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