Case study:River Dearne at Mexborough: Difference between revisions
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|Caption=Narrowed channel with increased velocities and riffles for fish spawning | |||
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|Caption=Main channel and back water five years on, 2000 | |||
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|Caption=New sinuous reed-fringed course following restoration | |||
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Revision as of 17:11, 25 July 2013
This case study is pending approval by a RiverWiki administrator.
Project overview
Status | Complete |
---|---|
Project web site | |
Themes | Fisheries, Flood risk management, Habitat and biodiversity |
Country | England |
Main contact forename | Chris |
Main contact surname | Firth |
Main contact user ID | |
Contact organisation | Don Catchment Rivers Trust |
Contact organisation web site | http://www.dcrt.org.uk/ |
Partner organisations | |
Parent multi-site project | |
This is a parent project encompassing the following projects |
No |
Project summary
The lower River Dearne had suffered substantial changes to its natural gradient as a result of subsidence problems cause by deep mining operations. To alleviate this problem a new straight and over-wide river was created in the 1970s to ensure efficient evacuation of floodwaters.
This resulted in physical uniformity of the channel, poor water quality and a lack of habitats for fish and other species.
The restoration scheme drastically reduced the width of the channel (10m to 5.5m) by creating a sinuous course and low flow channel using large boulders to create berms. Flood capacity was maintained by ensuring the in-channel structures were kept to a low level and the berms were designed to be submerged during high flow events. The design included three small backwaters and scrapes and the low berms were created at a variety of levels to enable the establishment of a range of riparian communities and provide habitats for a range of species.
Monitoring surveys and results
Lessons learnt
Catchment and subcatchment
Site
Name | River Dearne at Mexborough |
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WFD water body codes | GB104027063173 |
WFD (national) typology | |
WFD water body name | |
Pre-project morphology | Straightened, Over-widened, Uniform |
Reference morphology | Sinuous, narrower low flow channel |
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 | Gravel |
River corridor land use | Agriculture (arable) |
Average bankfull channel width category | |
Average bankfull channel width (m) | 5.55.5 m <br />0.0055 km <br />550 cm <br /> |
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) | 500500 m <br />0.5 km <br />50,000 cm <br /> |
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Project started | 1995/05/01 |
Works started | |
Works completed | |
Project completed | 1995/09/01 |
Total cost category | 10 - 50 k€ |
Total cost (k€) | £43,000"£" is not declared as a valid unit of measurement for this property. |
Benefit to cost ratio | |
Funding sources |
Cost for project phases
Phase | cost category | cost exact (k€) | Lead organisation | Contact forename | Contact surname |
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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 | |
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Hydromorphology | Channel pattern/planform |
Biology | Fish |
Physico-chemical | |
Other reasons for the project |
Measures
Structural measures
| |
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Bank/bed modifications | Adding sinuosity |
Floodplain / River corridor | Creation of backwaters |
Planform / Channel pattern | Backwaters created, Channel narrowing |
Other | |
Non-structural measures
| |
Management interventions | Reduced maintenance (est. £2, 500-£3, 000 reduction in maintenance costs per year) |
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: Abundance | Yes | Yes | Yes | 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
Image gallery
Additional documents and videos
Additional links and references
Link | Description |
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http://www.therrc.co.uk/pdf/manual/MAN 3 6.pdf | RRC Manual of River Restoration Techniques entry |
Supplementary Information
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