Pevensey Bay Sea Defences PPP Ian Thomas, Pevensey Coastal Defence Project Manager Monitoring & loss of sediment from the beach foreshore In Partnership with

Pevensey Monitoring Typical monitoring only to MLWS Often intermittent – annual/bi-annual survey? Reality – need whole sediment system Cost – merge land & marine surveys Dilemma – cost v potential savings

Problems covering full tidal area Pevensey Monitoring Pevensey No marine surveys undertaken Monthly GPS surveys from 2003 Each on lowest monthly spring tide Contract volumes above 0.0mOD Operationally need lower Measure to at least -2.5mOD Problems covering full tidal area

Monitoring - Embankment Toe position ±15m? Toe height ±1.5m?

Monitoring – Sand Terrace Toe runnel Offshore bar? Gradient Large banks & ponds Small bars & hollows

Monitoring – Sand Terrace Limited access time, large area Going below toe brings problems; weather - waves tidal cycle - equinox time of year - daylight Health & Safety silt build-up water depth  Survey quality falls Embankment width Foreshore width

Monitoring – Results 2003-2015 Net loss = c120,000 m³ in 12 years Average 2.07m Average 2.04m 4.04m 3.89m Net loss = c120,000 m³ in 12 years

Why Lowering Foreshore? On receding coasts, lower foreshore levels also fall   Holding the crest position, levels still fall  

Why Lowering Foreshore? Sovereign Harbour man-made built 1993 maintained access annual dredging 35 - 50,000 m³ deposited offshore

What Can Be Done? Reuse of maintenance dredging material Crown Estate – UK wide issue? Best use of dredged material? Potentially fund research Review existing Pevensey Bay data? Review other research findings? 2014 applied for MMO FEPA license Reuse of maintenance dredging material

Channel Coastal Observatory 2013 Swath Bathymetry Processed Results License variation March 2015 New Deposition site

Reuse of maintenance dredgings May 2015 Deposited 22 loads c17,000m3 of sand

The Future? East bit…. Sediment already moved Where? How quickly? What next? Monitor sea bed currents? Extended bathymetric surveys? How long to detect changes?

The Future? ConScience Unlikely to be unique to Sovereign Harbour Improve understanding of processes Bathymetry, currents, sediment movement Need to take Shoreface or Coastal Foundation view ConScience EC 6th Framework Programme (2007 – 2010) Followed EUROSION (2002 – 2004)

Management Principles www.conscience-eu.net “… the implementation of a scientifically based sustainable coastal erosion management in Europe.” Management Principles Coastal Sediment Cell Favourable Sediment Status Strategic Sediment Reservoir Coastal Resilience Days/metres Years/kms Decades/10 -100kms

The Future? Unlikely to be unique to Sovereign Harbour Improve understanding of processes Bathymetry, currents, sediment movement Need to take Shoreface or Coastal Foundation view What is effect of these losses? Improve re-use of dredged material Increasing importance to coastal managers Over 25 years = 250,000m3 loss… …increasingly difficult to “Hold the Line”

Thank you www.pevensey-bay.co.uk