Case study:Kensworth Quarry Chalk Pit Restoration

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Location: 51° 51' 56.35" N, 0° 31' 15.49" W

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Project overview

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Status	Planned
Project web site
Themes	Environmental flows and water resources, Habitat and biodiversity
Country	England
Main contact forename	Adam
Main contact surname	Hillier
Main contact user ID
Contact organisation	Ver Valley
Contact organisation web site	http://Self%20Employed
Partner organisations
This is a parent project encompassing the following projects	Kensworth Quarry Chalk Pit Site Restoration

Kensworth Quarry

Project summary

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Kensworth Quarry is the UK's largest chalk pit and is one of the largest in the world. It is located to the top of the Chilterns ridge close to the (now dry) head valleys of the River Ver which is is one of only 200 Chalk streams in the world.

The River Ver, like many other Chiltern chalk streams, has suffered from unsustainable water abstraction to support local development needs. Over the past decade the river has ceased to flow on the Chilterns dip slope above Redbourne and without hydro-support it is quite possible that the river will disappear above St Albans within the next couple of decades.

It is thought that River Ver has been flowing in this area since the Anglian Glacation 400,000 years ago and there may be a fantastic and unique opportunity to secure its future for a while longer.

Production from Kensworth Quarry is due to cease within the next decade after which it will be subject to a site restoration program. It is proposed that as part of the site restoration plan consideration be given to establishing a permanent perched reservoir as the focus of wetland nature reserve and 'Geopark' of international significance. The reservoir would also be used to provide head water support to the River Ver to revitalise the river and sustain flow throughout the year. In addition the perched reservoir could be used to as a pumped hydro energy storage facility to support the growing network of solar energy plants in the farmlands west of the Chilterns ridge.

Monitoring surveys and results

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The project is in the very early evaluation stage focusing on stakeholder outreach, regional planning advice and technical advice in hydro-engineering and pumped hydro storage assessment.

Preliminary work suggests a short pipe line connection from the perched reservoir to the source of the River Ver could provide 3000 litres per second of flow support to the river for up to 30 days.

Lessons learnt

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There are no lessons learnt as yet.

We are keen to get insights from any similar projects targeting river flow restoration/support through perched reservoirs derived from upland mining operations.

Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Site Edit site Name Kensworth Quarry and upper Ver Valleys WFD water body codes 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 Yes Invasive species present Yes Species of interest Dominant hydrology River bed now dry through much of the year above Redbourne Dominant substrate Chalk 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 Hydropower for distressed chalk stream system Hydromorphology Biology Physico-chemical Other reasons for the project Creating and internationally significant wetland reserve and Geopark. 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