Case study:Dam removal at Grönkullen, River Rolfsån

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Location: 57° 40' 21", 12° 35' 57"
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Project overview

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Status Complete
Project web site
Themes Fisheries, Habitat and biodiversity, Hydropower
Country Sweden
Main contact forename Andreas
Main contact surname Bäckstrand
Main contact user ID User:Arolam
Contact organisation Länsstyrelsen västra Götalands län
Contact organisation web site http://projektwebbar.lansstyrelsen.se/rolfsan/Sv/folj-atgardsarbetet/Pages/soran.aspx?keyword=gr%C3%B6nkullen
Partner organisations Municipality of Bollebygds
Parent multi-site project

Case_study:Biologisk återställning i Rolfsåns vattensystem

This is a parent project
encompassing the following
projects
No
Grönkullen stream (photo. Maria Arola)

Project summary

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Grönkullen hydro power station is located in one of the upstream tributaries of River Rolfså, River Sörån. Restorations took place after the county administrative board wanted to make migration possible for lake dwelling brown trout in lake Lygnern. Because a chemical plant and a railway are situated next to the river and there is a possible concentration of chemicals in the river, investigations were accomplished to find out whether the dam removal has any effect to the stability conditions. Conclusion was that there would not be any significant effect of the dam removal to the stability or water levels of the river. Investigations were made in 2002-2004 and the municipality of Bollebygds bought the plant 2005 to be able to remove the dam.

Restoration was done in 2005. A new river was rebuilt upstream and downstream of the old dam, altogether along a 200 m stretch. A small part of the old dam was saved as a reminder of how it once was. Stones and gravel were added to the river bank. Total cost of the restoration was about 5 million Swedish crones (ca. 500 000 euros).

Monitoring surveys and results

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Lessons learnt

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Image gallery


Downstreams from the dam(photo. Maria Arola)
Part of the old dam (photo. Maria Arola)
Removed dam (photo. Maria Arola)
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Catchment and subcatchment

Catchment

River basin district Skagerrak and Kattegat River basin
River basin Rolfsån River Basin

Subcatchment

River name River Rolfsån
Area category
Area (km2)
Maximum altitude category
Maximum altitude (m)
Dominant geology Organic (i.e. Peat)
Ecoregion Fenno-Scandian Shield
Dominant land cover Woodland, Intensive agriculture (arable)
Waterbody ID



Other case studies in this subcatchment: Apelnäs fishway at River Rolfså, Biologisk återställning i Rolfsåns vattensystem, Bosgården nature-like fishway at River Rolfså, Restorations of River Nolån-Hulta dam removal, ´Restorations of River Nolån-Bypass channel in Hulta Hydro power plant, ´Restorations of River Nolån-Fishway in Forsa hydro power plant, Ålgårda nature-like bypass channel at River Rolfsån


Site

Name Grönkullen hydro power station
WFD water body codes
WFD (national) typology
WFD water body name River Sörån
Pre-project morphology Artificial bed, Artificial channel, Embanked, Over deepened, Over-widened
Reference morphology
Desired post project morphology
Heavily modified water body Yes
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest Lake dwelling brown trout
Dominant hydrology
Dominant substrate
River corridor land use Woodland
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) 200
200 m
0.2 km
20,000 cm
Project started 2002
Works started 2005/08/01
Works completed 2005/10/31
Project completed 2005/10/31
Total cost category 500 - 1000 k€
Total cost (k€) 500
500 k€
500,000 €
Benefit to cost ratio
Funding sources

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring

Supplementary funding information

The total costs were about 5 million Swedish crones including investigations, purchase of appropriate rights and their implementation, demolition of the dam and river restoration measures.



Reasons for river restoration

Mitigation of a pressure Barriers to fish migration, Hydropower
Hydromorphology Continuity for organisms, Quantity & dynamics of flow
Biology Fish
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Barrier removal, Bed raising
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

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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