Case study:Pevensey Sea Defences

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Location: 50° 48' 13.89" N, 0° 29' 24.70" W

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Project overview

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Status	Complete
Project web site	http://www.therrc.co.uk/sites/default/files/projects/61_pevensey.pdf
Themes	Economic aspects, Flood risk management, Social benefits
Country	England
Main contact forename	Ian
Main contact surname	Thomas
Main contact user ID
Contact organisation	Pevensey Coastal Defence Ltd
Contact organisation web site	http://pevensey-bay.co.uk
Partner organisations	Environment Agency, Boskalis Westminster Ltd, Balfour Beatty, Mackley
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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The sea defences at Pevensey Bay in East Sussex (Map 1) are managed by Pevensey Coastal Defence Ltd (PCD) under a 25 year (2000 to 2025) public–private partnership (PPP) contract. The scheme is funded day to day by PCD. However, the contract is flexible enough to accommodate change. The sediment deficit of 30,000m3 on the Pevensey frontage is replenished in 2 ways: • Recharge from offshore – as dredged material from Owers Bank (near Littlehampton) is rainbowed onto the beach at the western end of the frontage. • Bypassing of material accumulated against the southern harbour arm around Sovereign Harbour (Photo 1) by road lorries – some 4,000–25,000m3 are moved per year with an annual average in recent years of 9,000m3. Under the PPP contract, PCD expects to receive 5,000m3 of material and pays for any over this amount. In addition: • Dredged material from the navigation channel adjacent to the harbour entrance is deposited below low water springs (this material is finer than material taken from the beach). This dredging is done by harbour owners, Premier Marinas, and not by PCD. PCD works with Premier Marinas to try and ensure suitable sediments are beneficially reused. About 40,000m3 have been reused in the last 2 years rather than being dumped at sea. • Recycling from the eastern end of the frontage westwards – this is done piecemeal, moving material various distances but rarely the full length of the frontage. Recycling volumes average about 100,000m3 annually.

Other flood risk management measures carried out by PCD on the frontage are beach profiling, constructing/maintaining retaining walls to hold beach material in place and maintaining around 7 groynes. The remaining 150 groynes on the frontage are not being maintained and had already deteriorated to a poor standard before the project started. The hybrid scheme improves responsiveness, flexibility and sustainability. The South West Beach at Sovereign Harbour is a highly volatile section of coast and sediment can build up to a point where it should be removed in days. PCD is best placed to initiate bypassing works at short notice. Bypassed material is only available between October and March, when dredgers generally find conditions are too rough for them to operate. Recharge and bypassing both represent Working with Natural Processes (WWNP).

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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 2000 Works started Works completed Project completed Total cost category Total cost (k€) £1m"£" is not declared as a valid unit of measurement for this property. Benefit to cost ratio Funding sources Public-private partnership, Partnership contributions 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 Flood and coastal erosion protection Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Beach nourishment 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