Beach replenishment delivers environmental bonus

Client Havant Borough Council, which has successfully employed this method in previous years, was enthusiastic to continue its strategy for coastal protection identified within their Eastoke Sectoral Strategy study.

Previously, the Council has worked in partnership with Chichester Harbour Conservancy maintaining the safe passage of navigation into Chichester harbour through dredging the approach channel and keeping dredged the material within the system. However, there was not sufficient material available for this campaign but Westminster Dredging was able to provide an alternative source of suitable material from a designated offshore aggregate area within their control.

Sospan Dau worked at Eastoke Beach on Hayling Island to deliver a total of 25,000 m³ of sea dredged aggregate direct to where it was needed, using the ‘rainbow’ technique to place the material ashore. Each ship load equated to some 45 lorry movements being taken off the local roads. Sospan Dau was well suited to the task and the constraints arising from the nature of the shoreline, being shallow drafted with a single spud forward which allowed a precise position on the beach to be held whilst discharging. At the other end of the cycle, the vessel also has the ability to dredge efficiently at the water depths encountered at the offshore aggregate licence areas.

Sophisticated navigation systems allow precise positioning of the vessel so that the aggregate can be discharged via the bow nozzle to a pre-determined location between the groynes on the beach. This allows Havant’s engineers to ensure that material is precisely placed for optimum protection of the shoreline.

The versatility of Sospan Dau demonstrates the principle that a vessel capable of performing a variety of tasks well, in this case everything from standard maintenance dredging in sometimes constricted harbours and channels to conventional sand winning and coastal protection works. Elsewhere within the Royal Boskalis Westminster fleet these same principles are also present, but on a significantly larger scale

The next step in the process will be for the recently established Havant & Portsmouth Coastal Partnership to secure the necessary funding to continue with essential coastal protection to reduce the potential of flooding through erosion of the natural defence system that the beach represents.