Case study:Upper Cringle Floodplain Restoration Project

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Location: 52° 49' 29.40" N, 0° 38' 55.40" W

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Project overview

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Status	Complete
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

Upper Cringle Brook Before and After Collagee

Project summary

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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

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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

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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.

Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name Upper Cringle Brook WFD water body codes GB105030051560 WFD (national) typology limestone river WFD water body name Cringle Brook - Upper Pre-project morphology Straightened, Over deepened Reference morphology Anastomosing Desired post project morphology Anastomosing Heavily modified water body Yes National/international site designation Local/regional site designations Protected species present Yes Invasive species present No Species of interest Dominant hydrology Groundwater Dominant substrate Clay, Gravel River corridor land use Grassland Average bankfull channel width category Less than 2 m Average bankfull channel width (m) Average bankfull channel depth category Less than 0.5 m Average bankfull channel depth (m) Mean discharge category Less than 0.1 m³/s Mean annual discharge (m3/s) Average channel gradient category 0.001 - 0.01 Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) 10001,000 m <br />1 km <br />100,000 cm <br /> Project started 03/02/2022 Works started 2022/02/03 Works completed 2022/04/30 Project completed 2022/04/30 Total cost category 50 - 100 k€ Total cost (k€) 9898 k€ <br />98,000 € <br /> Benefit to cost ratio 2.97 Funding sources Environment Agency Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design 10 - 50 k€ 1414 k€ <br />14,000 € <br /> Lincolnshire Rivers Trust Gail Talton Stakeholder engagement and communication Less than 1 k€ Lincolnshire Rivers Trust Gail Talton Works and works supervision 50 - 100 k€ 8484 k€ <br />84,000 € <br /> Lincolnshire Rivers Trust Gail Talton Post-project management and maintenance Less than 1 k€ Lincolnshire Rivers Trust Gail Talton Monitoring Less than 1 k€ Lincolnshire Rivers Trust Gail Talton Supplementary funding information Works were paid for by a Water Environment Improvement Fund Grant and land was contributed to the project by the landowner. Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Land drainage Hydromorphology Channel pattern/planform Biology Invertebrates, Macrophytes and/or phytobenthos: Average abundance Physico-chemical Nutrient concentrations, Oxygen balance Other reasons for the project Landscape enhancement Measures Edit Measures Structural measures Bank/bed modifications Introducing large woody debris Floodplain / River corridor Lowering of floodplain, Wildflower meadows Planform / Channel pattern Back channel created, Channel naturalisation, Creation of an island, Creation of pond, Creation of backwater, Habitat creation Other Non-structural measures Management interventions Associated terrestrial habitat improvements Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Channel pattern/planform Yes Yes No Yes No Awaiting results Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Invertebrates: Diversity No Yes Yes Yes Yes Awaiting results Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Nutrient concentrations No Yes No Yes Yes Awaiting results Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Case study Upper Cringle Brook White Heath Plantation Restoration.pdf Cringle aerial before photo Cringle aerial after photo.JPG Before restoration pic early Feb 22.jpg Post restoration pic late Feb 22.jpg Additional links and references Edit links and references Link Description http://lincsrivers.org.uk/upper-cringle-brook-gets-a-makeover/ Press Release Supplementary Information Edit Supplementary Information