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

2. 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

3. 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

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

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

6. 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

7. 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

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

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

10. 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

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

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

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

14. 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)

15. Management Principles
“… 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/ kms

16. 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”

17. Thank you