Case study:Southern Water Lukely Brook

Project overview

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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

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Project summary

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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.

Lukely Brook upstream of Clatterford

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

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Horse Paddock and Plaish Meadows Stage Zero schemes:

• Hydrometric monitoring at 5 surface water locations (stilling wells) and 5 shallow groundwater monitoring locations in the floodplain was undertaken to monitor impacts of the Phase 1 Schemes on water levels:

1. June 2017-March 2019: 3 surface water monitoring locations, 2 groundwater monitoring locations and 1 barometer were installed in June 2017). The automatic water level monitoring devices conducted regular stage board and manual water level readings were downloaded and processed the data until March 2019.
2. November 2017-May 2022: Loggers and recorded stage board were downloaded and manual dip readings recorded as part of baseline monitoring.
3. May 2022-October 2024: 2 further surface water, 3 further groundwater and 1 barometric monitoring locations were added. Regular stage board and manual groundwater level readings were reinstated as part of this project.

• Visual imagery collected by repeat aerial imagery surveys every 6 weeks from May 2022 to Autumn 2024 using a DJI Mini drone, as well as time lapse and fixed-point photography to monitor the evolution of the sites over time.
• Aquatic ecology surveys conducted in spring and autumn from April 2022 to Autumn 2024 to track any changes in macroinvertebrates as a result of the Stage Zero schemes in the channel and floodplain.
• Water quality data collected at 6 locations quarterly from March 2023 to Autumn 2024 track any changes in water quality over time.
• National Vegetation Classification (NVC) surveys in 2018, 2022 and 2023 to track changes in floodplain vegetation as a result of the Phase 1 Schemes.
• Bird monitoring has also been undertaken monthly following the construction of the schemes from November 2022 to April 2023.

The following open-source datasets from local monitoring stations were also used to supplement the site data:

• Daily rainfall data from Carisbrooke rainfall gauge (Station ID: 333195)
• Hourly barometric pressure from Met Office weather station at Saint Catherine’s Point.

For the other schemes at Sheep Dip Field, Spring Lane and Towngate Pond:

• Aquatic ecology surveys conducted in spring and autumn from April 2022 to Autumn 2024 to track any changes in macroinvertebrates as a result of all Phase 2 Schemes.
• National Vegetation Classification (NVC) surveys in 2018, 2022 and 2023 to track changes in floodplain vegetation in Sheep Dip Field only.
• Visual imagery collected by repeat aerial imagery surveys every 6 weeks from May 2022 using a DJI Mini drone (Sheep Dip Field only), as well as fixed-point photography to monitor the evolution of the sites over time.
• Bird monitoring has also been undertaken monthly prior to the construction of the Sheep Dip Field from November 2022 to April 2023.

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

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Project background

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Reach length directly affected (m)
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
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring

Catchment and subcatchment

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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

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Mitigation of a pressure	Abstraction, Barriers to fish migration, Drinking water storage and supply
Hydromorphology	Connection to groundwaters, Flow velocities, Freshwater flow regime, Quantity & dynamics of flow
Biology	Fish, Invertebrates, Macrophytes
Physico-chemical
Other reasons for the project

Site

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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)
Average channel gradient category
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Average unit stream power (W/m2)

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Location: 50° 41' 27.13" N, 1° 18' 39.28" W

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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