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 Select a catchment/subcatchment Site Edit 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 Edit 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 Edit reasons for restoration Mitigation of a pressure Land Drainage and Flood Risk Hydromorphology Biology Fish Physico-chemical Phosphate Other reasons for the project Measures Edit 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 Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative 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 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 Papermill Weir In-channel Restoration (Tree Hinging and gravel) Case Study.pdf Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information