Case study:Broadwater Brook

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Location: 50° 49' 32.02" N, 0° 21' 3.73" W

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Project overview

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Status	Complete
Project web site
Themes	Habitat and biodiversity, Land use management - agriculture, Social benefits, Water quality, Urban
Country	England
Main contact forename	Peter
Main contact surname	King
Main contact user ID	User:Oartpk
Contact organisation	Ouse & Adur Rivers Trust
Contact organisation web site	http://www.oart.org.uk
Partner organisations	Sompting Estate Trust, Environment Agency SSD, Heritage Lottery Fund
Parent multi-site project
This is a parent project encompassing the following projects	No

File:New River Channel

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Project summary

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This urban chalk stream project has realigned the course of the Broadwater Brook, removing it from underground pipes and setting a new route through agricultural fields. Previously degraded from pollution entering from industrial areas and the main road network we have installed sediment traps at the upstream extent and have ensured vegetation establishment in the channel to further filter pollutants. Allowing for low flows (as a ephemeral stream) the stream is narrow with marginal shelves to provide wetland habitat whilst being flooded during heavy rainfall. The surrounding land has been transformed from arable maize fields into 6.9ha of wildflower meadow with 2.2km of new hedgerow and 500 trees forming a shaw woodland. Additional habitat in the form of three ponds, a re-wilding zone and scrapes have been formed along the riparian zone. The project tackled land contamination from neighbouring landfill along with accumulations of arsenic from previous land use. A mains sewer was realigned and mitigation for a chemical effluent pipe and mains power cable were also needed to complete the project which also had to content with a 1:3000 gradient and artificially raised ground through the centre of the site.

The project has been co-designed and delivered with the local community with numerous activities and events inspiring and raising awareness of chalk streams and the impact of urban living which has inspired behavioural change. Over 1000 members of the local community have been involved in the project whether through volunteering on practical tasks, attending educational events or being involved in one of the citizen science monitoring programmes. The site is now open to the public for the first time along a newly created Sompting Brooks River Trail which includes interpretation and artworks depicting the areas historical association with water.

Monitoring surveys and results

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We have been monitoring the effectiveness of silt traps within the system along with taking water sample for chemical analysis. In addition we have undertaken BMWP sampling for freshwater invertebrates as well as ecological surveys for reptiles and amphibians, fish, birds, dragonflies, bats, harvest mice and macrophytes. All of these were also undertaken for 2 years before the project started to generate a baseline status for the site. Results show that, across all parameters, water quality is significantly improved and that the sediment traps are working in all but the most extreme flow conditions. Species diversity across the site has grown from a recorded 100 species in 2017/18 to 535 species in 2021. Five fish species have been recorded within the new channel (from none within the old channel). The site has also recorded the first Scarce Blue Tailed Damselfly in Sussex for 125 years, one of 18 species of Odonata now recorded on the Brooks. Water quality sampling has revealed significant amounts of nitrate being released from the aquifer over winter which has highlighted a need for further investigation of land management practices to the north of the project area.

We have also been monitoring impacts on the local community and results show a better appreciation and understanding of the water environment, that co-design and delivery has ensured guardianship of the site into the future and that providing outdoor opportunities in heavily urbanised areas is of great value to wellbeing and community cohesion. All results of the project will be available on the website from January 2022 - www.oart.org.uk/epic

Lessons learnt

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We used local contractors to provide ECI assistance during the development of designs, this resulted in large costs increases (even from the ECI) at tender and we would ensure that more consideration is given to the right contractor providing this advice from the beginning of the project. Relied on existing relationships and partnerships to provide solutions to constraints on site which meant no legal framework was in place for agreed actions and organizations changed their approach to elements of the project at the last minute. In future we would ensure that legal agreements are in place around service mitigation prior to appointing a contractor. We did not appreciate or appropriately consider the ground contamination constraints at an early enough stage. A lack of prior experience of these issues and relying on previous reports led to misunderstanding the costs and constraints this would cause. For future projects we would ensure, where potential land contamination is present, that early involvement of experts is obtained, and budgets reflect possible additional costs. We have also learnt that, through perseverance, projects which many believe to be unachievable due to costs and constraints can be delivered in a manner which is cost beneficial and provide multiple benefits to people and wildlife.

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Catchment and subcatchment Select a catchment/subcatchment 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 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 Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications 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