Case study:Unit 3a – Hurst Bridge 2013

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Location: 50° 42' 48.30" N, 2° 17' 26.03" W

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Project overview

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Status	Complete
Project web site	http://www.environment-agency.gov.uk
Themes	Fisheries, Habitat and biodiversity, Hydromorphology
Country	England
Main contact forename	Alastair
Main contact surname	Maxwell
Main contact user ID
Contact organisation	Environment Agency
Contact organisation web site	http://www.environment-agency.gov.uk
Partner organisations
Parent multi-site project	Case_study:River Frome Rehabilitation Plan
This is a parent project encompassing the following projects	No

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Project summary

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The main River Frome Unit 3a flows mostly through the Moreton Estate. This reach in particular is downstream of the Hurst road bridge. It was historically part of an old mill system and the reach retains a fixed crest weir at the location of the former mill. Removal of the weir was discounted early on due to costs and possible impacts on the road bridge. Works were concentrated on the reach between the bridge and the weir looking to improve the channel and bank structure and creating a greater range of habitats in particular for fish.

The River Frome Rehabilitation Plan states the main proposals to improve the SSSI condition and WFD objectives of Unit 3a and to incorporate as part of the Hurst Bridge Project are: a) increase / diversify channel bed profile creating deep pools and gullies and b) to introduce large woody debris to provide in channel habitat and vary bed profiles through scour and deposition.

Monitoring surveys and results

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Lessons learnt

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This project did pose some issues during its delivery. The extent of the berm creation and bed reprofiling was limited due to the presence of overhead power lines. A safe working method was implemented by the Ops Delivery team. Initially the excavator to be used had an 8m reach; this was also used on the North Channel job. However this reach was wider and to maximise the benefits of the project a long reach had to be brought to site. This came at additional cost but enabled effective delivery of the project. The long reach machine was also used on a few parts of the North Channel project which were out of reach form the original machine. The tree works described above were also able to be carried out with the larger machine.

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district South West River basin Dorset Subcatchment River name Frome Dorset (Lower) & Furzebrook Stream Area category 100 - 1000 km² Area (km2) Maximum altitude category 200 - 500 m Maximum altitude (m) 223223 m <br />0.223 km <br />22,300 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB108044009690 Other case studies in this subcatchment: 2e Lower Woodsford River and Floodplain Enhancement, Bockhampton Enhancement, Hurst Bridge (downstream), Louds Mill (Downstream)m Enhancement, Lower Bockhampton, Lower Woodsford, Martins River Island, Moreton Channel Gravel Reprofiling, North Channel Upper Reach, River Frome Rehabilitation Plan... further results Site Edit site Name WFD water body codes GB108044009690 WFD (national) typology WFD water body name Frome Dorset (Lower) & Furzebrook Stream 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) 150150 m <br />0.15 km <br />15,000 cm <br /> Project started 2013/01/01 Works started Works completed Project completed Total cost category Total cost (k€) 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 Hydromorphology Channel pattern/planform, Flow velocities Biology Physico-chemical Other reasons for the project To meet Natural England’s target for standard conditions, Improve SSSI condition Measures Edit Measures Structural measures Bank/bed modifications Introducing large woody debris, habitat improvements 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 Project Record Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information