Case study:Removal of a pond weir in a tributary of Petersbach

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Location: 48° 58' 58", 7° 15' 2"
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Project overview

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Status Complete
Project web site
Themes
Country France
Main contact forename Julien
Main contact surname Prinet
Main contact user ID
Contact organisation ONF – direction forêt Alsace
Contact organisation web site http://www.onf.fr
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
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Project summary

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The Saumuehle stream is a 1,5 Km tributary of the Petersbach river, located in the Petite Pierre Nord forest. It is a firs class fish stream. In 1980, the Saumuehle pond (12000 m2) was created for recreational fishing. The pond cause warming waters downstream and the weir is an obstacle to ecological continuity. After a few years, the dam, made with soil from the excavation of the pond, lost its seal and the water level had dropped, leading to a gradual filling of the pond. Under an Interreg project which aims to improve the condition of the river in the forest, this site was chosen as a pilot site. The work takes place in several phases. At first, the pond is drained in order to remove the drain boards After conducting a fishing rescue and temporary diversion of the river to a side ditch, materials of the dam are moved on the edge of the pond. Then, reprofiling sloping instead of the dam is made. A lateral pond is created to hold the presence of amphibians observed on the site.

Monitoring surveys and results

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This restoration has reconnecting 1400 linear meters of stream. After draining the pond, the river quickly regained a sinuous channel. The substrate is unclogged and coarse aggregate appeared; also riffles and mouilles appeared upstream. A post-work fishing monitoring shows clearly a recolonization of the brown trout upstream. In 2008, during winter floods, the bed of the stream moves a few meters on the left bank, where the new pond was created. This was quickly picked up by the river. This has proven that the pond was created too early: It would have to wait until the stabilization of the river bed. This pond will be recreated when the bed is completely stabilized.

Lessons learnt

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Image gallery


The Saumuehle Pond before works.
The Saumuehle pond weir removal, during works in 2007.
The Saumuehle stream, in 2008, 6 months after pond drainage.
The coarse substrate reappeared after works (March 2008).
The Saumuelhe stream in December 2009, two years after restoration works.
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Catchment and subcatchment

Catchment

River basin district Rhin-Meuse
River basin

Subcatchment

River name Petersbach
Area category
Area (km2)
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion Western Highlands
Dominant land cover
Waterbody ID



Site

Name Petite-Pierre Nord forest - Butten
WFD water body codes FRCR437
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations Parc naturel régional des Vosges du Nord
Protected species present Yes
Invasive species present No
Species of interest brown trout, sculpins, minnows and white-clawed crayfish
Dominant hydrology
Dominant substrate
River corridor land use Plantation forestry
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 100
100 m
0.1 km
10,000 cm
Project started
Works started 2007/09/01
Works completed 2007/11/01
Project completed
Total cost category
Total cost (k€) 1,136
1,136 k€
1,136,000 €
Benefit to cost ratio
Funding sources EU Interreg IIIA (50 %), Agence de l’eau (25 %), conseils généraux du Bas-Rhin et du Haut-Rhin (15 %), direction régionale de l’environnement (DIREN) (5 %)

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Sycoparc, Office national de l’eau et des milieux aquatiques (Onema) - service départemental, direction régionale de l’environnement (DIREN), agence de l’eau.
Stakeholder engagement and communication
Works and works supervision 1,136
1,136 k€
1,136,000 €
Sycoparc, Office national de l’eau et des milieux aquatiques (Onema) - service départemental, direction régionale de l’environnement (DIREN), agence de l’eau.
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Barriers to fish migration
Hydromorphology Continuity of sediment transport
Biology Fish: Abundance
Physico-chemical Temperature
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Weir removal, Pond drainage
Floodplain / River corridor
Planform / Channel pattern
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish Yes Yes No Yes No Improvement

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



Additional documents and videos


Additional links and references

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Supplementary Information

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