Case study:River Idle Hallcroft (Tiln) Weir Fish Pass

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Location: 53° 20' 34.58" N, 0° 57' 39.44" W

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Project overview

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Status	In progress
Project web site
Themes	Fisheries
Country	England
Main contact forename	Chris
Main contact surname	Bradley
Main contact user ID
Contact organisation	Environment Agency
Contact organisation web site
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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To meet targets set by the Water Framework Directive (WFD), the Environment Agency are undertaking a programme of habitat improvement works on the River Idle which is a major tributary to the River Trent. This project concerns Hallcroft Weir (AKA as Tiln Weir) in Retford, Nottinghamshire (SK69275 83396).

Hallcroft Weir, located on the River Idle in Nottinghamshire is approximately 30-35km from the confluence at which the Idle meets the tidal Trent. Not including the sluice / pumping station control structures at the confluence, Hallcroft weir is the first physical barrier encountered by upstream migrating fish. Although currently passable to some species of fish, a combination of head loss and flow limits certain species ability to pass the weir.

Hallcroft Weir is an Environment Agency owned asset. The weir is a broad crested type weir spanning the full channel width and running perpendicular to the flow. Downstream of the weir is a rock ramp extending from approximately 1m downstream of the weir toe for 15m.

The weir at Hallcroft currently acted as a barrier to free movement of fish, particularly in an upstream direction. It was impassable to many species of fish under most flow conditions due to velocity and depth of flow.

The project aim was to increase the migratory ability of all fish species in the River Idle and in particular eels. This will lead to a more sustainable population within the catchment as the work will allow the migrating eels and other fish species to reach more spawning grounds.

The total project costs are determined to be £147,200.

Monitoring surveys and results

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Following implementation of the fish pass improvements, we will monitor the impact through on-going survey work, which can be compared to past survey results. We have long term monitoring sites up and downstream of Hallcroft weir that have been monitored since the 1990’s - upstream at Eaton and downstream at Chain Bridge. Samples are usually taken in early May, so there will be a sample just before the project takes place and then we will get post project result the following May. These standardised monitoring results can also be compared to catch returns from the local angling clubs.

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Image gallery

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Before works

The weir crest following debris removal

Larger boulders forming the channel bank toe

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Humber River basin Idle and Torne Subcatchment River name River Idle from Maun/Poulter Conf to Tiln Area category 100 - 1000 km² Area (km2) Maximum altitude category 100 - 200 m Maximum altitude (m) 105105 m <br />0.105 km <br />10,500 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB104028058091 Site Edit site Name WFD water body codes WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body National/international site designation Local/regional site designations Protected species present Invasive species present 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) Project started 2011/08/31 Works started 2015/04/06 Works completed 2015/06/23 Project completed Total cost category 100 - 500 k€ Total cost (k€) 208208 k€ <br />208,000 € <br /> Benefit to cost ratio Funding sources Environment Agency Flood and Coastal Risk Management 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 Barriers to fish migration Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications rock ramp construction 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 Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information