Case study:Upper Cringle Floodplain Restoration Project
Project overview
Status | Complete |
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Project web site | http://lincsrivers.org.uk/upper-cringle-brook-gets-a-makeover/?msclkid=6925b300d11011ecbd85ed27680329e8 |
Themes | Environmental flows and water resources, Flood risk management, Habitat and biodiversity, Hydromorphology, Water quality |
Country | England |
Main contact forename | Gail |
Main contact surname | Talton |
Main contact user ID | User:LincsRivers |
Contact organisation | Lincolnshire Rivers Trust |
Contact organisation web site | http://lincsrivers.org.uk |
Partner organisations | |
Parent multi-site project | |
This is a parent project encompassing the following projects |
No |
Project summary
The Limestone Becks are located over a 3,000km2 limestone ridge in the west of Lincolnshire and are supplied by consistent flows of high-quality groundwater. They are isolated and unique, and if in good condition, have potential to support a rich aquatic flora and fauna, rarely found in Eastern England.
Cringle Brook is a 12km limestone beck exemplifying both good and poor river habitat. The lower sections of the Brook remain relatively natural whilst the Upper Cringle Brook, historically straightened and deepened, faces a range of pressures including deterioration in habitat quality through changing management practices and diffuse pollution from the wider catchment, damaging it to such an extent it is substantially poorer ecologically.
The current overall WFD status is moderate with invertebrates and macrophytes at moderate (2019 classification).
Cringle Brook is also a catchment for supply of public drinking water, currently closed due to elevated pesticide concentrations. The site is also downstream of Skillington village waste-water treatment plant where phosphate treatment options are limited. A separate project is being undertaken in the wider catchment to address diffuse pollution however, it is anticipated that the new wetland areas created by this project will help provide some degree of natural attenuation.
The project location at the top of the Witham catchment was deemed ideal as natural processes could be used to make space for water and help trap sediment. This project included 1km of the Upper Cringle Brook, which was un-farmed, dry floodplain, with the deepened and straightened channel running along the Southern edge. The channel and floodplain were completely disconnected, and the channel habitat was very poor.
Previous experience in the Upper Witham Catchment has shown that the only effective option for restoration is to provide the river with a floodplain. In-channel measures alone would not make a worthwhile improvement. This is why other options were not considered.
1 ha (the maximum area agreed by the landowner) of inset floodplain was excavated along the 1km stretch with secondary channels, back channels and ponds added and some trees from the site were pulled across the new floodplain, enabling natural processes to be restarted, creating diversity and sinuosity in the channel. Without this action, the habitat will not be improved and a WFD reason for failure will not be addressed. Spoil generated from the excavations was used on the same site to create a 1.7 ha wildflower area adjacent to the floodplain.
Monitoring surveys and results
A Morph River Condition assessment survey was carried out before with a follow up survey later in the summer and a further one in a year. Ecological surveys also carried out prior to project will be compared to surveys to be carried out next year to assess ecological impact. Results are expected to show a significant improvement in habitat and ecology along the restored 1km stretch. Drone video footage was recorded before and afterwards showing the extent of the works and the increased water storage capacity of the newly instated inset floodplains. Fixed point photography of the floodplain over time will be used to study sediment deposition. Phosphate levels will also be measured upstream between water treatment works and project site and compared with downstream of site to monitor ‘polishing’ effect of floodplain reconnection along the stretch. Baseline data from EA gauging stations should provide evidence of the volume of water storage made available by the and the possible reduction of peak flows in Upper Witham system.
Lessons learnt
Head waters should not be discounted as a place to look to restore even when restoration seems unfeasible due to current condition. The benefits can be significant.
When lowering floodplains, considering how the material can be landscaped on site and used for other benefits e.g., wildflower habitats but understanding that the site to look a bit stark whilst this establishes.
The value of an experienced site supervisor and a skilled contractor cannot be underestimated. Confidence in the contractor's experience enabled them free reign to be creative within the constraints of the given inset floodplain parameters, and to observe and work with the river gives a more organic approach (regular site checks ensure all going to plan and landowner completely happy).
Concise and transparent communication with landowner to build trust is key, enabling a more flexible approach on the broader principles of work as they were set out, facilitating a more natural approach from the contractors on the ground.
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Other case studies in this subcatchment: Aubourn Rock Ramp and Habitat Works, Belton Floodplain Reconnection and River Restoration, Dysart Park, Grantham Habitat Improvement, Grantham Blue Green - Urban Reach, Little Ponton, Manthorpe Floodplain Reconnection, Papermill Weir Section in-channel restoration, River Witham Great Ponton, Stainby Road, Colsterworth, Syston and Barkston Restoration... further results
Site
Project background
Cost for project phases
Supplementary funding informationWorks were paid for by a Water Environment Improvement Fund Grant and land was contributed to the project by the landowner.
Reasons for river restoration
Measures
MonitoringHydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Any other monitoring, e.g. social, economic
Monitoring documents
Additional documents and videos
Additional links and references
Supplementary InformationEdit Supplementary Information
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