Sidmouth Beach Management Plan: Offshore islands would reduce the need to raise the splash wall

At today’s meeting of the steering group of the Beach Management Plan, the ‘preferred Option’ was considered:

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Agenda for Sidmouth and East Beach BMP Project Steering Group Thursday, 22nd August, 2019, 2.00 pm

To: Sidmouth and East Beach BMP Project Steering Group

Venue: Kennaway House, Sidmouth

1 Welcome and apologies

2 Notes from the previous meeting and terms of reference. (Pages 2 – 8) Notes from the previous meeting held on the 9 August 2019. The terms of reference are also included as these have been updated for membership following Annual Council in May 2019.

3 Recap on Beach Management Scheme project (Pages 9 – 48) John Golding, Strategic Lead Housing, Health and Environment will provide a recap of the project. Included in the agenda papers is the business case as it stands. You can also view the information on the project displayed at the exhibition and the posters on the coastal scheme.

4 Revision of preferred option Presentation update from Royal Haskoning DVH

5 Partnership funding update

Sidmouth Beach Management Plan meeting > August agenda

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The problem is that the ‘preferred Option’ is not preferred by most of the community representatives:

Futures Forum: Beach Management Plan: Option 4b or not 4b >>> or: how to ignore everyone else’s opinion

Futures Forum: Beach Management Plan: Town Council chooses breakwaters to protect and regenerate beach >>> further reports

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Another element discussed was that of the proposed Splash Wall – which has been immensely unpopular among townsfolk:

Futures Forum: Beach Management Plan: a ‘preferred option’ is an extra half-a-metre high wall along Sidmouth’s promenade

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It now seems that the increased height on top of the existing wall  will be further increased by another few centimetres:

… from the height of 0.5m proposed over a year ago:

Sidmouth beach splash wall raised to stop erosion – but offshore breakwaters too expensive – Devon Live

… to 0.6m, or 24 inches, as proposed in the report attached to the minutes of the latest meeting – according to which, adding this on the height of the sea wall will make no difference to the views of the sea from a car…

SBMPSG 220819 Agenda v2

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On the one hand, the need for the splash wall and its height are based on current climate change and sea level rise predictions. They are very likely to go up because scientists are worried the world will not be able to meet the targets for the reduction greenhouse gas emissions. If that happens the splash wall may well need to be raised again.

On the other hand, the draft Environment Agency strategy for flood and coastal erosion says walls are not sustainable, we can not keep on raising them.

Walls Won’t Save Our Cities From Rising Seas. Here’s What Will

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However, the height of the splash wall is also linked to the height of the beach and offshore conditions. So an offshore island, as was originally proposed by Posford Duvivier in 1990, would reduce the need..

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A correspondent explains:

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Waves break when they move from deep water to shallow water. So a shallow foreshore will cause waves to break there before they reach the beach.

If the foreshore is not shallow and waves reach and break on the beach, then the higher the beach the less the broken wave will run up it, and the wider the beach the less chance there is of a broken wave reaching the sea wall and overtopping it onto the prom.

The less over topping there is, the less is the need to raise the splash wall.

In other words:

Offshore islands, breakwaters or reefs would reduce the need to raise the splash wall.

Here’s a picture of shore parallel breakwaters in action in Norfolk:

AERIAL PHOTOGRAPH OF ARTIFICIAL REEF OFFSHORE BREAKWATER AT SEA PALLING ON THE NORFOLK COAST

Compare that with Halcrow’s daunting illustration of shore parallel breakwaters for Sidmouth (option 4) below, which got rejected.

Notice how poorly illustrated the tombolos are and how closely spaced (over engineered) the shore parallel breakwaters are, which will have inflated the cost estimate and got shore parallel breakwaters and tombolos, like those in Norfolk, rejected. 

It is very possible that shore parallel breakwaters (or oblique ones) and tombolos like those in Norfolk would have enthused the residents and business in Sidmouth and attracted more local funding and tourism grants etc. This might have made it possible to build them and remove the rock groynes which harm Sidmouth’s beauty and tourist economy.

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See also:

Futures Forum: Beach Management Plan: looking for funding for the ‘technically preferred’ option 4b

   
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