Case study:River Dearne at Mexborough
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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 |
|---|---|
| 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 /> |
|---|---|
| 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 |
|---|---|---|---|---|---|
| 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 | |
|---|---|
| Hydromorphology | Channel pattern/planform |
| Biology | Fish |
| Physico-chemical | |
| Other reasons for the project |
Measures
Structural measures
| |
|---|---|
| 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 |
|---|---|
| http://www.therrc.co.uk/pdf/manual/MAN 3 6.pdf | RRC Manual of River Restoration Techniques entry |
Supplementary Information
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