Swanage Bay. Groynes. Sea Walls. Collapsed Cliff wall. Gabions. Pre 2005. Beach Recharge. Aim: - Protect Swanage from coastal erosion - Will also improve the amenity for all residents and visitors. Left untouched = £35 million damage over 50 years . Beach Recharge.
Aim: - Protect Swanage from coastal erosion
- Will also improve the amenity for all residents and visitors.
Left untouched = £35 million damage over 50 years
Old groynes been in place for 75 years
Plan: - build 19 timber groynes along the sand
- replenish beach with 160,000 tons of sand
- stabilise erosion and lead to a bigger beach.
A pipeline (sinkerline) approx 750m long x 700mm diameter is floated into position and then sunk to the seabed during replenishment work.
At the seaward end the sinkerline is coupled to a 36m flexible riser pipe section, followed by a 100m flexible floating pipeline. With assistance from the multicat, the dredger couples to the floating pipeline via a bespoke coupling ball-joint system.
At the landward end the sinkerline is fitted with a steel flange from which sections of shoreline pipe (approximately 12m long) can be coupled to discharge sand to the required locations. Y-pieces with valves can be introduced to the pipeline to direct the loads to different areas of the beach.
Sand bunds are pushed both toward the seawall (for protection) and towards the shoreline to retain the new sand on the beach and avoid losses to the foreshore. The sand/water mixture from the pipeline flows in between these bunds where it settles on the beach, with the water returning to sea.
Work started at Swanage on Tuesday, 22nd November and was completed on Friday, 9th December 2005