Case study:Papermill Weir Section in-channel restoration

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Location: 52° 53' 55.31" N, 0° 37' 36.18" W
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity
Country England
Main contact forename David
Main contact surname Hutchinson
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site http://Environment%20Agency
Partner organisations SKDC, Wild Trout Trust and Grantham Angling Association Fly Fishing Section
Parent multi-site project

Case_study:Upper Witham Restoration

This is a parent project
encompassing the following
projects
No
Hinged Trees following works

Project summary

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This project was undertaken to improve river habitat in a section of the Upper Witham downstream of a large weir. Despite flowing through an area of woodland with good riparian wetland habitat and some sinuosity, the bed material was almost exclusively large cobbles. Very little gravel was available for trout spawning, as a result of the interruption of natural sediment transport processes by the weir. In addition, there was little woody material habitat in the river. The project to address this occurred in two phases. In 2022, the Blue Green Corridor project led by SKDC worked in conjunction with Grantham Angling Association (Fly Fishing Section) to hinge existing trees into the river to create berm features and also secured trunks that fully spanned the river. The latter aiming to create scour pools underneath. In 2023, the Wild Trout Trust completed the works by adding gravel onto the sill of the weir at the upstream extent of the reach. In subsequent high flow events, including Storm Babet, the gravel could then naturally start to move into position downstream.

Monitoring surveys and results

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This is a routine EA fisheries survey site so we will be able to monitor the long term impact of the changes over the next few years. The movement of gravel features is being monitored and post high flow events winter 23/24 we are seeing near bar and riffle features forming in the wooded section.

Lessons learnt

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It has worked well to do this project in two phases, firstly with the addition of the wood and secondly with the gravel. Particularly where living willow has been used, it will allow the woody material to establish before trapping the gravel as it moves downstream over time.

The use of natural wood found on site and the placement of gravel at a single point with good access have proved very cost effective compared to a constructed riffle approach.

If safe to do so, gravel is best added in high flows to avoid the requirement for people in the channel to rake it flat. The high flows will naturally and quickly sort the gravel into position. The gravel used was 5 – 20mm size range; in future a 20 – 40mm component should also be included to match the naturally-occurring size range in the Upper Witham.


Image gallery


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Catchment and subcatchment

Catchment

River basin district Anglian
River basin Witham

Subcatchment

River name Upper Witham
Area category 10 - 100 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 4646 m <br />0.046 km <br />4,600 cm <br />
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105030056760



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, River Witham Great Ponton, Stainby Road, Colsterworth, Syston and Barkston Restoration, Upper Cringle Floodplain Restoration Project... further results


Site

Name Papermill weir section
WFD water body codes GB105030056780
WFD (national) typology
WFD water body name Witham - confluence of Cringle Brook to confluence Brant
Pre-project morphology
Reference morphology
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
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) 350350 m <br />0.35 km <br />35,000 cm <br />
Project started 01/11/2023
Works started
Works completed
Project completed
Total cost category 10 - 50 k€
Total cost (k€) 2340023,400 k€ <br />23,400,000 € <br />
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 Land Drainage and Flood Risk
Hydromorphology
Biology Fish
Physico-chemical Phosphate
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Tree hinging and adding gravel.
Floodplain / River corridor
Planform / Channel pattern
Other
Non-structural measures
Management interventions
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

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

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Supplementary Information

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