POOLE BAY – NEARSHORE REPLENISHMENT TRIAL

WHY “Working with nature” approach -Placing sand on the sea bed to see if the waves will move the sand onto the beach. Efficiencies – aim to work with local maintenance dredging operations. “learn by doing” – modelling not possible.

How Contract required the sand to be placed in a 150 x 150 m square box with the smallest possible footprint. Actual placing was discussed on the dredger Licence condition sand not higher that 2mCD actual height was 1m CD. After 3 days reduced to 2mCD.

Second AWAC position First AWAC position

Dredger record of placed loads

Monitoring Silt movement. Turbidity Sand movement bathymetric, topographic surveys and tracer sand.

First Bathymetric survey of completed placement

EARLY TRACER RESULTS

21st May 2015

21st May 2015

LEVEL DIFFERENCE PLOT

SINGLE BEAM SURVEY 27 MAR 2015

MULTIBEAM SURVEY 7TH APRIL 2015

OBSERVATIONS Tracer identifies sediment movement onto beach and beach parallel. (none offshore) Volume difference 17 Feb – 25 Feb = 800m3 25 Feb – 7 April = 1800m3 27 Mar – 9 July = 4500m3

Further Monitoring. Bathymetric (November and March) Topographic ( November and March) Silt sediment completion March 2016 AWAC in second position until March 2016 Photo’s to record change in beach shape.

Both published on www.Poolebay.net CCO -Reports Pre-monitoring Report May 2015. Interim Monitoring Report July 2015. Both published on www.Poolebay.net 2016 Final report.

Further Discussion. HR Wallingford have recently completed a post project appraisal for another scheme and concluded that 80% of sand moves along our coast frontage in the water. Do we know how important this is? Are we investing enough in nearshore monitoring? Of the 20% moving along the beach how much is wind blown and how much is littoral drift?