Case study:River Gelsa at Bevtoft

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Location: 55° 12' 3.48" N, 9° 12' 15.83" E

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity
Country	Denmark
Main contact forename	Nick
Main contact surname	Elbourne
Main contact user ID
Contact organisation	River Restoration Centre
Contact organisation web site
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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From July to September 1989 a 1.3 km reach of the river which had historically been straightened and channelised, was restored to a 1.9 km meandering course. Rip-rap structures were created in the new meanders using 1000 m3 of stone. 740m3 of gravels were used to create new spawning grounds. In total sixteen new meanders were created, transforming the in stream morphology, decreasing channel width by 3-4m and reducing discharge capacity by around 50%. Sinuosity also increased from 1.15 and 1.60. A weir structure was also demolished just upstream of the project area as part of the restoration design. A similar upstream reach was left in the original channelised state to act as a benchmark against which improvements in the restored channel could be measured. An extensive maintenance regime of dredging and mechanical weed clearance was altered to weed clearance by scythe, and later to no human intervention. This reach represents an alternative option for restoration, which relies on natural processes to take over without human intervention. Post project monitoring was carried out in May in 1990, 1991, 1993 and 1995, as well as pre project monitoring. Results of monitoring showed nearly three times the macroinvertebrate population present post restoration. Numbers in the upstream reach which was left unaltered also increased between 1990 and 1995. Brown trout recovered to pre-restoration levels but not beyond. The results also showed that the River Gelsa had stabilised by 1993, with changes in substrate and macroinvertebrate composition mainly taking place between 1993 and 1995. The unaltered reach also showed impressive natural recovery, indicating that the termination of maintenance practices can have a substantial effect on the stream environment. Additional of gravels would further improve the channel and could provide a very cost effective restoration strategy. Nineteen years after restoration works were completed, hydromorphological conditions in the restored channel have developed in a very similar way to the unaltered channel. This supports the view that natural recovery without human intervention can be as effective as planned restoration.

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment

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Catchment

River basin district	Ribe Å
River basin	Ribe Å

Subcatchment

River name	Gelsa
Area category
Area (km2)	975975 km² <br />97,500 ha <br />
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion
Dominant land cover	Intensive agriculture (arable), Broadleaf/mixed woodland (semi natural)
Waterbody ID

Site

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Name	Bevtoft
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology	Straightened, Over-widened
Reference morphology	Low gradient passively meandering
Desired post project morphology
Heavily modified water body	No
National/international site designation
Local/regional site designations
Protected species present	No
Invasive species present	No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use	Intensive agriculture (arable), Improved/semi-improved grassland/pasture
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

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Reach length directly affected (m)	13001,300 m <br />1.3 km <br />130,000 cm <br />
Project started	1989/07/01
Works started
Works completed	1989/09/01
Project completed	1989/09/01
Total cost category	more than 10000 k€
Total cost (k€)
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

Reasons for river restoration

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Mitigation of a pressure	Riparian development, aquatic habitat development
Hydromorphology	Channel pattern/planform, Quantity & dynamics of flow
Biology	Fish, Invertebrates
Physico-chemical
Other reasons for the project

Measures

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Structural measures
Bank/bed modifications	Construction of meanders
Floodplain / River corridor
Planform / Channel pattern	Channel naturalisation; Creation of new meandering channel
Other
Non-structural measures
Management interventions	ceased maintenance regime
Social measures (incl. engagement)
Other

Monitoring

Hydromorphological quality elements

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quality elements

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

Biological quality elements

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quality elements

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative
Invertebrates: Diversity	Yes	Yes	No	No	Yes	Improvement
Invertebrates: Abundance	Yes	Yes	No	No	Yes	Improvement

Physico-chemical quality elements

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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

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

Monitoring documents

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Image gallery

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Additional documents and videos

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Additional links and references

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Link	Description
http://www.youtube.com/watch?v=9JVpm G9yKU

Supplementary Information

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Friberg, N., Kronvang, B., Svendsen, L.M., Hanse, H.O., Nielsen, N.B. (1994). Restoration of a channelized reach of the River Gelså, Denmark: Effects on the macroinvertebrate community. Aquatic Conservation: Marine and Freshwater Ecosystems, 4 (4), 289-296.