Next stage of Cowes Breakwater proceeds

Cowes Breakwater

The CHC Commissioners met on 3 July for an Extraordinary Board Meeting to consider the formal Cowes Breakwater Project review that addressed the issues of changes in tidal flows and potential changes to the sedimentation regime as a result of the 2014 breakwater construction. The Commissioners received a presentation from their consultant hydrodynamic engineers and, after careful and detailed consideration, unanimously agreed to proceed with the scheduled 2015 breakwater construction and the placement of the rock armour.

CHC has informed harbour users of the changes to tidal flows that occurred after the construction of the Cowes Breakwater gravel core in September 2014. The extensive pre-breakwater construction tidal modelling carried out did predict certain changes to the tidal rates and directions within the harbour, but CHC recognises that differences have been noted between the predicted modelling outputs and actual flows observed and recorded. In addition, concerns have been raised by a number of harbour users regarding potential increased levels of siltation occurring within the harbour.

As a result, CHC determined it would be appropriate to carry out the full and formal ‘special project review’ to provide the best available advice for the Board to consider and inform the decision on whether to proceed with or delay the 2015 breakwater construction.

CHC presented information on tidal and sedimentation issues to the Advisory Committee at their meeting on 23 June including information on the data, surveys and modelling evidence. The decision required – to proceed or to delay the breakwater works – was considered including associated risks and wider impacts. The Advisory Committee concluded that there was not enough evidence to warrant a delay and supported continuing with the next stage of breakwater construction.

The Commissioners agreed at the Extraordinary meeting, the importance of completing the new hydrodynamic model and its use in reviewing the design optimisation of the next phases of the Cowes Breakwater Project. The next phases being the dredging of the new Eastern Channel and extension of the Shrape breakwater. They also confirmed their commitment to another formal project review and stakeholder consultation before finalising any decisions on the next phases of the project.

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