Morphological restoration of temporary watercourses in the National Forest of Chaux

General

National Id

France_13

Summary

The Chaux forest is a silvicultural production area and is covered by a large number of small streams, originally winding and of small size. In 2008, the LIFE program "Ruisseaux de têtes de bassins et faune patrimoniale associée" ([Pond head creeks and associated heritage fauna]) carried out restoration work at the head of the catchment area on part of the small ditches of the Chaux national forest. Based on the experience and results obtained, the National forest office (ONF) proposed a new project to restore 45 km of watercourses in three 15-km sections (2015, 2017 and 2018) with the objective of significantly restoring the hydraulic functioning of the Clauge and improving the conservation status of the species covered by the Habitats Directive. Indeed, all the temporary tributaries of the Clauge were transformed in the 1960s into deep straight ditches via canalization works.

Light or indepth?

In-depth

The in-depth description of the case study

mnre_rex08_foret_de_chaux.pdf

Location description

The Chaux forest is covered by a large number of small streams, originally winding and of small size (more than 400 km). They are located at the head of the catchment area and are tributaries of the Clauge.
The lime forest is a silvicultural production area (mainly oak), the environment is described as quite common.

NUTS Code

Franche-Comté

RBD code

FR43-Franche-Comté

Transboundary

Source(s)

Reconstitution des écoulements de surface de deux affluents temporaires de la Clauge amont

Dossier de demande d’autorisation au titre de la Loi sur l’Eau et les Milieux Aquatique et de Natura 2000

NWRM(s) implemented in the case study

Coarse woody debris

Wetland restoration and management

Re-meandering

Longitude

5.6601

Latitude

47.0813

Monitoring maintenance

Monitoring parameters

A monitoring protocol was set up in 2017 with the University of Franche-Comté (technical assistant) and the ONF (National Office of Forest), with the help of 2 master trainees.
Entomological monitoring
Monitoring is carried out in the spring, at the net and in the watercourses and is led by the University. Entomological monitoring is carried out before and after, at a control site, and at restored sites, with a time grid every two and three years. The control shows that the observed changes are not due to climatic variations.
Piezometric monitoring (individual or online).
About twenty piezometers have been installed with weekly automatic readings.
Dendrometric monitoring
At the level of the piezometers, vegetation monitoring plots are placed by the ONF (height, diameter, health status, dominance) on control plots of 1000m². The population evolution will be monitored over the long term.

Performance

Biophysical impact assessement method

Comparison with a control site.

Design & implementations

Project scale

Large

Application scale

River Basin

Installation date

2015

Area (ha)

2 700 ha

Area specifications

Restored watercourse represents 45 km

Favourable preconditions

Almost all the temporary tributaries of the Clauge being originally meandriformes, a remeandering operation is justified following their transformation in the 1960s into deep rectilinear ditches, so that they can regain a hydrological functioning that allows them to support an associated biodiversity.

Design contractual arrangement

Arrangement type	Responsibility	Role	Comments	Name

Design consultation activity

Activity stage	Key issues	Name	Comments

Design land use change

Land use change type

Design authority

Authority type	Role	Responsibility	Name	Comments
Other	Initiation of the measure	Responsible	National office of forest (ONF)
Research institute / University	Monitoring	Supporting	Franche Comté science university

Lessons, risks, implications...

Success factor(s)

Success factor type	Success factor role	Comments
		The fact that the streams are very degraded allowed to have a very degraded zero state and therefore a strong reaction after the works.

Financing

Financing type	Comments

Barrier

Barrier type	Barrier role	Comments
Legal obligations / restrictions	main barrier	The main constraint was the completion of the public inquiry, since it represents a significant cost, and also a duration of 6 to 8 months.

Driver

Driver type	Driver role	Comments
Other	main driver	The fact the habitat was seriously degraded and other experience of successful restoration of habitat on a similar area was a key driver, as positive results were already forecasted from the beginning.

Financing share

Financing share type	Share	Comments

Policy, general governance and design targets

Policy description

The naturally straight portions were either overburied, widened or both; the downstream flow velocity of the floods was accelerated accordingly.
This channelization resulted in a lowering of the altitude of the associated surface water tables, but also in a spreading of the flow water slide in the stream, excluding flood peaks, as well as an increase in energy in the minor beds during high water periods.
The expected results were: Restoration of water flows and Overall habitat improvement

Policy target

Target purpose

Policy pressure

Pressure directive	Relevant pressure

Policy area

Policy area type	Policy area focus	Name	Comments

Policy impact

Impact directive	Relevant impact

Policy wider plan

Wider plan type	Wider plan focus	Name	Comments

Policy requirement directive

Requirement directive	Specification

Socio-economic

Information on Ecosystem improved biodiversity

Biodiversity monitoring reveals a better attractiveness of the spawning sites for amphibians (frogs, salamander, newt, reproduction multiplied by 10) and amphibians because the river was not initially biogenic;
It also reveals an improvement in habitat for entomofauna, with the number of taxa multiplied by 2, a recovery by ephemeropterans, perlids and trichopterans protected at the European level (e. g. Hagenella clathrata classified as endangered (EN) on the IUCN Red List). There is also an improvement in quality (i.e. more demanding species that are dependent on wetlands).

Biophysical impacts

Information on Increased groundwater level

Piezometric monitoring shows an increase in the hydroperiod (+15 days) because the time of presence of water in the watercourse is longer, as these are surface aquifers that are in silts and dry in summer, water is more available for trees in spring. When the time of presence of water in the stream is extended, it is also extended in the groundwater table.

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