Case study:River Somer channel enhancement, Midsomer Norton

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Location: 51° 17' 8.66" N, 2° 28' 55.68" W

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity, Social benefits
Country	England
Main contact forename	Luke
Main contact surname	Kozak
Main contact user ID
Contact organisation	Woodland, Water and Gardens
Contact organisation web site
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

River Somer on the high street post-restoration (Woodland water and gardens)

Project summary

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The reach of the River Somer flowing through Midsomer Morton had been a focus of concern for many years. A complete lack of vegetation, weir impoundment and large amounts of silt accumulation were severely effecting habitat and amenity potential of the channel. This was in stark contrast to the natural brook up and downstream of the town.

Local residents formed the River Somer Management Team (RSMT), with the aim of improving the channel based around the following project objectives:

• Removal of three weirs
• Build new channel based on the geomorphology of the “natural” stretches of the River Somer
• To enhance the aesthetic value of the reach, including the development of vegetated margins, in channel flow regime and opportunities to engage with the public
• Restore habitats and enhance ecological value
• “bring trout to the town”
• Use localised materials
• Use construction techniques which are flood resistant
• Community engagement for construction, long term maintenance and educational opportunities

The project was split into four stages:

1. Weir removal
2. Berm construction
3. Bed raising and fine adjustment
4. Planting aquatic margins

The RSMT commissioned Woodland, Water and Gardens (Luke Kozak) as project consultants, designers and construction managers. BANES were commissioned as the overall project managers. Construction started in May 2011 taking three weeks to complete. The planting phase was completed by volunteer Midsomer Norton residents. The berms were constructed from coarse interlocking local limestone which did not exceed 30cm high. This allowed flow to be released over the berms, increasing channel capacity when needed (2-stage channel design). Flow events shortly after construction demonstrated the effectiveness of this design. In June 2012 the first formal assessment took place post-project completion. This encompassed fish, invertebrate and vegetation assessment. The report concluded that: berms were intact and in good condition despite several high flow events, plant communities had matured well providing a diverse habitat, maintenance carried out by volunteers has helped to keep the channel litter free. Diversity of aquatic organisms has increased, and although some small silt deposits have form in low energy areas the channel in generally self-cleansing. The project has been given a civic “Pride of Place” award for environmental enhancement, and the establishment of the RSMT will ensure the success of the project into the future.

The River Restoration Centre would like to thank Luke Kozak (Woodland, Water and Gardens) as well as Dominic Longley for providing the information and photographs for this case study.

Monitoring surveys and results

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Lessons learnt

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Image gallery

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channel prior to restoration (woodland water and gardens)

channel one year after completion of works (woodland water and gardens)

local community group helping to complete the planting phase (woodland water and gardens)

channel during construction (woodland water and gardens)

laying out berm design (woodland water and gardens)

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Severn River basin Bristol Avon and North Somerset Streams Subcatchment River name Wellow Bk - source to conf Snails Bk Area category 10 - 100 km² Area (km2) Maximum altitude category 200 - 500 m Maximum altitude (m) 220220 m <br />0.22 km <br />22,000 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Improved grassland Waterbody ID GB109053022250 Site Edit site Name River Somer at Midsomer Norton WFD water body codes GB109053022250 WFD (national) typology WFD water body name Wellow Bk - source to conf Snails Bk Pre-project morphology Impounded, Over-widened, Straightened Reference morphology 2-stage channel, Pool-riffle, Sinuous 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 wild brown trout Dominant hydrology Dominant substrate Artificial River corridor land use Improved/semi-improved grassland/pasture, Intensive agriculture (arable) 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) 167167 m <br />0.167 km <br />16,700 cm <br /> Project started 2011 Works started 2011/05/02 Works completed 2011/05/23 Project completed 2011/05/31 Total cost category 10 - 50 k€ Total cost (k€) Benefit to cost ratio Funding sources fundraising by the River Somer Management Team 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 sediment accumulation, Barriers to fish migration, Urbanisation Hydromorphology Continuity of sediment transport, Continuity for organisms Biology Fish, Invertebrates Physico-chemical Other reasons for the project improving local town centre, Community demand Measures Edit Measures Structural measures Bank/bed modifications Weir removal, Creation of berms, Bed raising, Planting of native species, Removal of sediment Floodplain / River corridor Planform / Channel pattern Channel naturalisation, Meandering channel Other Non-structural measures Management interventions management of litter, management of undesirable plant species Social measures (incl. engagement) creation of River Somer Management Team, fundraising Other Participation in maintenance, Participation in works 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 Fish Yes Yes No No No Improvement Invertebrates Yes Yes No No No Improvement 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 general assessment of habitat quality and diversity (repeat photography) Yes Yes Yes No No Improvement 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 A public consultation meeting was held pre restoration in Midsomer Norton, roughly late 2010 – no documentation is available. A project assessment report undertaken by Woodland, Water & Gardens (Luke Kozak) identified stakeholder engagement as a key part of the future of the project. Recommendations for this included: -An increased presence of ornamental plants to please residents who dislike the "wild" look of channel vegetation -Interpretation boards to identify in-channel plants and animals -Sculptural representation of "creatures of the River Somer" constructed from local stone, wood or wrought iron -Formal ecological tours of the channel, specifically for school children -Regularly updated bulletin board including section to log "recent sightings"