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The meeting received a presentative from Amy Savage, Principal Consultant at Royal HaskoningDHV, on the Southwold Harbour Investment Plan. The presentation covered the project conclusions, including options for the harbour entrance structures, and proposals for dredging of the shoal bank and channel narrowing.
Mrs Savage summarised the project aims which were to develop an investment plan for the harbour to ensure future operations and survivability. The main issues to be addressed were the poor condition of the South Pier, mooring conditions at the North Wall and the influence of the future estuary tidal prism.
Mrs Savage summarised the modelling so far, including what would happen if no action was taken and the impact of the entrance structure failure on the town of Southwold and the wider estuary. The entrance structures had a residual life of <10 years for the South Pier, and >30 for the North Pier (assuming the South Pier was repaired).
Ms Savage stated that at present the preferred option for the South Pier was to replace it with a rock breakwater which would improve conditions in the entrance and at the North Wall. Additional design work was needed to refine the plan to replace the South Pier, including the alignment of the replacement structure and the positioning of culverts (to replicate the tidal flow through the ‘windows’ in the existing structure), and whether dredging in the channel could be included as part of these works and what the impact of this would be. Construction costs would then need to be updated to reflect the increases in construction costs in the last two years.
Mr Pickles asked whether the Environment Agency were managing the banks on the estuary or not. Officers confirmed that they were beginning to withdraw from management, those in the Harbour were being maintained at present, but they had withdrawn upstream. Mrs Savage confirmed that they might be managing banks by clearing vegetation, they may not be undertaking more extensive maintenance work or making repairs.
The Head of Operations confirmed he would speak with the Environment Agency on behalf of the Council and the Committee to confirm what their strategy was to the management and maintenance of the estuary.
Mr Pickles asked what protection the South Pier provided aside from protecting the North Pier. Mrs Savage confirmed it did reduce wave penetration into the Harbour and at the north Wall, and limited sediment movement into the Harbour.
Mrs Savage summarised another option which had been considered as part of the study to narrow the channel opposite the North Wall to reduce water levels upstream. Other issues that needed to be addressed were the flood risk to the Harbour Road and neighbouring businesses, taking into account sea level rise, and the risk of failure of the estuary banks.
With regards to dredging of the shoal bank, this had not yet been fully assessed or modelled. Mrs Savage summarised the initial comments on the benefits and constraints of doing this. The bank did not appear to be growing, and feeling was that if it was removed it would not come back quickly, although it could reform if there was a significant storm or similar event. Mrs Savage commented that the entrance channel was fairly stable at the moment and as a result it was likely that the bank would not reform in the short term, but more work would need to be done to confirm this and the impact of dredging on the flow rates, general silting and the position of the main channel.
Mr Pickles asked how much debris entered the Harbour from Dunwich Creek. Mrs Savage confirmed that the initial surveys had included samples from around the entrance to the Creek, but not within the Creek itself.
Councillor Cook commented that the benefits of dredging seemed to outweigh the risks, and would allow easier access to the the Harbour by both businesses and visitors and make the North Wall more usable.
The Head of Operations summarised that there seemed to be a consensus on changes to the South Pier and dredging, but more work needed to be done on the modelling. Subject to modelling, this could be moved forward more quickly than other projects. With regards to protections for Harbour Road this was more difficult and would take more work to look at the impact of this on businesses and access. Works further upstream would require a lot more work as they included land which was outside the harbour’s control, and would require discussions with other agencies.
Mrs Savage confirmed that the existing South Pier structure would not have to be totally removed but could form part of the new structure.
Councillor Beavan referred to an inner breakwater and extending the narrow channel, and commented that the two could work well together. He added that he would be concerned about dredging upsetting the equilibrium of the Harbour an having unintended consequences. Mrs Savage commented that how the options would work together was not clear yet, and work needed to be done to see how all the options would work in more detail so work could begin.
The Head of Operations confirmed he would discuss the extra modelling options with Royal HaskoningDHV for the shoal bank and refine the options for the channel narrowing alongside this.