Case study:Pevensey Sea Defences

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Location: 50° 48' 14", -0° 29' 25"
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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
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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



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
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Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
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Average channel gradient
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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

Mitigation of a pressure Flood and coastal erosion protection
Hydromorphology
Biology
Physico-chemical
Other reasons for the project


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

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

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Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



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Additional links and references

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Supplementary Information

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