Case study:River Gelsa at Bevtoft

From RESTORE
Jump to: navigation, search
0.00
(0 votes)


To discuss or comment on this case study, please use the discussion page.


Location: 55° 12' 3", 9° 12' 16"
Edit location
Loading map...
Left click to look around in the map, and use the wheel of your mouse to zoom in and out.


Project overview

Edit project overview
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
Courtesy of Google Street Map, 2013.

Project summary

Edit project overview to modify the project summary.


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

This case study hasn’t got any Monitoring survey and results, you can add some by editing the project overview.

Lessons learnt

This case study hasn’t got any lessons learnt, you can add some by editing the project overview.


Image gallery


ShowHideAdditionalImage.png


Catchment and subcatchment

Catchment

River basin district Ribe Å
River basin Ribe Å

Subcatchment

River name Gelsa
Area category
Area (km2) 975
975 km²
97,500 ha
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion
Dominant land cover Intensive agriculture (arable), Broadleaf/mixed woodland (semi natural)
Waterbody ID



Site

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

Reach length directly affected (m) 1300
1,300 m
1.3 km
130,000 cm
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

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

Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern Channel naturalisation, Meandering channel, Creation of meanders
Other
Non-structural measures
Management interventions ceased maintenance regime
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
Invertebrates: Diversity Yes Yes No No Yes Improvement
Invertebrates: Abundance Yes Yes No No Yes 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

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

Supplementary Information

Edit Supplementary Information

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.