Royal HaskoningDHV explain the methodology they have used to create proposals for reducing wave overtopping and the risk of flooding to Sidmouth
The Sidmouth and East Beach Management Scheme steering group received a positive update from East Devon District Council’s project consultants, Royal HaskoningDHV, when it met on 10 May 2018 to learn what progress had been made in completing the outline design, environmental impact assessment and outline business case for the scheme.
The meeting followed on from a well-attended public exhibition on 19 April 2018 at which Royal HaskoningDHV presented the background to the scheme and the proposals to recharge both Sidmouth Beach and East Beach, add a groyne onto East Beach, and increase the height of the existing splash wall. Over 150 people attended the event and the public exhibition page on the East Devon website received over 100 views.
At the steering group meeting, Royal HaskoningDHV explained how they had considered and tested various approaches to reducing the rate of wave overtopping, including increasing the width and height of the beach. However changes in the design of the beach profile are limited by the geometry of the existing groynes and provide a limited reduction in flood risk.
Royal HaskoningDHV’s thorough tests and methodical approach has resulted in a proposal to recharge the beach with a 10m flat section at the top, and a suggested increase in the height of the splash wall of up to 0.5m from its existing level, with sections of lower height where the beach is less exposed.
East Devon and Royal HaskoningDHV emphasised that during the design development, they have been conscious of the potential impacts that a higher splash wall might have on the town. Raising the height of the splash wall is a proposal that will continue to be considered very carefully as the outline design progresses. In addition, East Devon will ensure that adequate allowance is made for enhancements to the wall in the forward funding case.
The issue of additional offshore breakwaters was also discussed and it was explained again that although the breakwaters may present a more robust solution technically, they would come at almost double the cost. Their cost has been re-examined recently by Royal HaskoningDHV and they have confirmed that the previous costings as part of the Beach Management Plan were correct.
Royal HaskoningDHV also presented some of the more detailed outline design drawings they are now working on, which have been developed with the use of 3D models to help ensure that costs for the volumes of rock and shingle are estimated accurately. Additional surveys are being carried out along the seafront to help inform the outline design of the splash wall.
The proposals also include improving maintenance access onto East Beach for future recycling and replenishment, and the issue of whether water access can be improved as part of this remains important to the steering group.
Sidmouth Lifeboat kindly offered to host a separate meeting with the interested groups to look at ways in which the scheme could improve the launching facilities at the Port Royal end of the beach.
It was good to meet with the group following the successful public exhibition event and to continue to hear their views and to keep the community updated as the scheme moves forward.
Alex Lee, Technical Director from Royal HaskoningDHV, said:
We enjoyed having the opportunity to update the statutory bodies and local community on our progress so far, and to explain the work that has gone on behind the scenes.