Case study:Southern Water Lukely Brook
Project overview
| Status | Complete |
|---|---|
| Project web site | |
| Themes | Environmental flows and water resources, Fisheries, Habitat and biodiversity, Hydromorphology, Land use management - agriculture, Monitoring, Social benefits, Urban |
| Country | England |
| Main contact forename | Matt |
| Main contact surname | Dempster |
| Main contact user ID | User:Southern Water Catchment Team |
| Contact organisation | |
| Contact organisation web site | |
| Partner organisations | AtkinsRéalis, FiveRivers |
| This is a parent project encompassing the following projects |
Project summary
The Lukely Brook is a Chalk winterbourne stream located on the Isle of Wight, flowing from the rural central downs north through Carisbrooke and into the Medina Estuary in Newport.
Southern Water operates two groundwater abstractions near to the Lukely Brook, which supply a large proportion of the Isle of Wight with clean drinking water. Southern Water has had a number of environmental regulatory undertakings as part of its AMP6 NEP (National Environment Programme) and AMP7 WINEP (Water Industry National Environment Programme), which aim to ensure that groundwater abstractions are environmentally sustainable in the long-term, and seeks to mitigate any quantified impacts resulting from water company abstraction on watercourses and the valuable ecological habitats they support.
under the AMP6 NEP and AMP7 WINEP, Southern Water have undertaken a programme of ecological and hydro-geomorphological improvement works on the Lukely Brook between 2020 and 2024 to improve the ecological resilience of this chalk winterbourne stream and adjacent ecologically designated floodplain meadows. The environmental enhancement works include the removal of a weir, installation of three fish passes, two ‘Stage Zero’ floodplain reconnection schemes, realignment and reprofiling of a historically modified section of channel, and removal of a weir along with reprofiling of banks in a town centre public amenity space. The final element completed in 2024 was restoration of the river channel though a disused highways ford next to Southern Waters water supply works in Carisbrooke. Successful delivery of the scheme has been achieved through partnership working with the Island Rivers/Newport Rivers Group and continued positive engagement and consultation with landowners and other local stakeholders.
Monitoring surveys and results
Water level monitoring:
The highly different antecedent conditions between May 2022 and October 2024 make it difficult to separate the impacts of the scheme from the overall hydrological signal, especially for sites with limited baseline data. Floodplain inundation in Horse Paddock occurred during a lower magnitude rainfall event and water was stored on the floodplain for longer duration post-scheme, than was seen in the baseline monitoring period. Extended periods of floodplain inundation have occurred since the scheme construction. Whilst the Plaish Meadow scheme may locally be extending the duration of elevated shallow groundwater levels in the floodplain into the summer months, this may simply be a reflection of the wetter conditions after the scheme has been implemented. Extended wetter conditions since the construction of the woody features suggests an increasingly wetter floodplain in both above and below ground water levels, but it is difficult to separate the effects of the scheme from the extraordinarily high rainfall between October 2023 and March 2024.
Visual imagery
Drone imagery and fixed-point photography have provided visual evidence of changes at each site. This was particularly pronounced at Horse Paddock where the floodplain vegetation has changed to become more aquatic and creating a diversity of flow types on the floodplain. The drone imagery was particularly effective here with shorter vegetation on the floodplain than Plaish Meadows. Floodplain inundation in Plaish Meadows was more responsive to high rainfall events, reconnecting temporarily in the local area surrounding the ford and Lukely Brook woody feature. The drone imagery also showed the woody features on the drains effectively working to slow and store flow, with macrophyte vegetation establishing in the channel. Drone imagery was less effective at this site as the tall vegetation made it difficult to see the extent of floodplain inundation. At Froglands Stream, the drone imagery has shown the recovery of bank and in-channel vegetation in response to the restoration showing clearly how the vegetation has narrowed flow, creating faster flowing riffle features. Fixed-point photos of Spring Lane and Towngate Pond have shown how the schemes have recovered following the disturbance of construction with vegetation establishment coming quickly following the implementation of both schemes.
Aquatic ecology – macroinvertebrate monitoring
Drought conditions were experienced before the implementation of schemes followed by wetter conditions afterwards. Thus, some initial changes in the macroinvertebrates are likely to show a gradual recovery over time with increased flows and sedimentation. There were notable differences in the macroinvertebrate community found at Horse Paddock compared to the other Lukely Brook sites, with Horse Paddock communities more associated with slower flows and a greater abundance of fine sediment. The majority of species were common, but the samples yielded a total of five nationally scarce species (the caddisfly Limnephilus hirsutus, long-horned soldierfly Vanoyia tenuicornis, pygmy soldier fly Oxycera pygmaea, white-barred soldier fly O. morrisii and the riffle beetle Riolus subviolaceus). At three sampling sites nationally scarce species (soldierfly, Oxycera pygmaea; white-barred soldierfly, Oxycera morrisii; the caddisfly: Limnephilus hirsutus and the long-horned soldierfly: Vanovia tenuicornis) were recorded at the sites for the first time following scheme construction and are associated with wetlands and marshes. Following an initial drop in taxon richness, macroinvertebrate indices from the re-meandered Froglands Stream increased post restoration showing a gradual recovery to pre-restoration levels and an improvement in habitat quality. Interesting changes were observed rapidly at Spring Lane following the tree removal and coppicing. Implementation of this scheme was later and hence the further monitoring will show how the scheme has responded to the additional narrowing. Following the removal of the weir at Towngate Pond, samples show an increase in diversity of mayflies, caddisfly taxa and riffle beetles, particularly in April 2024, perhaps due to favourable flow conditions. The increase in post-restoration LIFE scores indicates an increase in flow velocity likely resulting from the weir removal.
Water quality
In general, concentrations of both phosphorus and nitrogen species were highest at the upstream end of Lukely Brook (at Horse Paddock and Plaish Farm monitoring sites), lowest at Plaish Meadows, and increased at Clatterford Shute, at the downstream end of the reach. The Fishpond Stream (which comes in on Plaish Meadows was noted as having good quality and potentially improving water quality downstream. The largest improvements in water quality were noted downstream of Plaish Meadows but is difficult to disentangle whether this was due to the schemes or whether this was primarily due to the improved water quality of the Fishpond Stream.
Vegetation monitoring
Little evidence of any significant changes to National Vegetation Classification communities although it was noted that communities could take time for a visible change to occur following the implementation of the various schemes.
Bird counts
The wetter floodplains have attracted birds that have been previously absent such as Jack Snipe, Common Snipe, Little Egret, Shelduck and Moorhen.
The monitoring is continuing for all schemes delivered in the second WINEP namely Horse Paddock, Plaish Meadow, Sheep Dip field, Spring Lane and Towngate Pond. Monitoring is scheduled to continue until 2030 but at reduced frequency. Currently, the monitoring report is being updated with the 2025 monitoring results.
Lessons learnt
Project background
| Reach length directly affected (m) | |
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| Project started | |
| Works started | |
| Works completed | |
| Project completed | |
| Total cost category | 500 - 1000 k€ |
| Total cost (k€) | |
| Benefit to cost ratio | |
| Funding sources | Southern Water WINEP |
Cost for project phases
| Phase | cost category | cost exact (k€) | Lead organisation | Contact forename | Contact surname |
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| Investigation and design | |||||
| Stakeholder engagement and communication | |||||
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| Post-project management and maintenance | |||||
| Monitoring |
Catchment and subcatchment
Edit the catchment and subcatchment details
(affects all case studies in this subcatchment)
Catchment
| River basin district | South East |
|---|---|
| River basin | Isle of Wight |
Subcatchment
| River name | Lukely Brook |
|---|---|
| Area category | 10 - 100 km² |
| Area (km2) | |
| Maximum altitude category | 200 - 500 m |
| Maximum altitude (m) | 216216 m <br />0.216 km <br />21,600 cm <br /> |
| Dominant geology | Calcareous |
| Ecoregion | Great Britain |
| Dominant land cover | Arable and Horticulture |
| Waterbody ID | GB107101006250 |
Reasons for river restoration
Site
| Name | Lukely Brook |
|---|---|
| WFD water body codes | GB107101006250 |
| WFD (national) typology | |
| WFD water body name | |
| 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) | |
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| Average channel gradient | |
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Measures
MonitoringHydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Any other monitoring, e.g. social, economic
Monitoring documents
Additional documents and videos
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Supplementary InformationEdit Supplementary Information
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