DEFRA commissioned the Environmental agency to look into flood coastal prevention (up to the A27 flyover) for the Arun-Peacehaven coastal area.

Proposal:

33 syenite (from Larvik, Norway = Larvikite?) rock sea defences, of which 3 are already in place, from the Church of the Good Shepherd to Lancing Beach Green.

Reason:

To replace old wooden greenheart sea defences which are nearing their end of their effective lifespan.
To prevent a catastrophic 1 in 200 years storm surge event. The wave action is considered important in any disaster scenario.
(This has never happened in living memory and the historical record of the last catastrophic English Channel storm was 1702. The North Sea Storm Surge of 1953 reached only as far south as north Kent.)
There are also plans to improve the river defences, à la Ricardos, on the River Adur. (A minor surge on the Adur occurred as recently as February 1983.)

Ecology

Derek Neate suggested that Widewater Lagoon is drying out and become lower because less water percolates through into the lagoon. As a regular user of this route for 40 years, I have never noticed any  long term change whatsoever, but before this the sea used to breach the shingle bank and there were Eels in the lagoon so the water levels may have been higher as recently as 50 years ago.

Derek Neate also suggest that by putting in the new rock defences (with extra shingle?) the percolation to the lagoon may be reduced or prevented altogether changing the ecology.

The remedy seems to be to install a controlled feeder pipeline from the sea.
 

Pipeline

450 mm diameter pipeline, gravity feed from and inlet on the seaward side below MHW, controlled by a unique Flow Control Chamber on the lagoon side. Grill but no fine filter.

Water levels to be monitored by a Committee comprising representatives from English Nature, Shoreham District Ornithological Society, Friends of Widewater Lagoon, West Sussex County Council, Environmental Agency, Lancing Parish Council, Adur District Council.
(None of these people are likely to know anything useful about intertidal or lagoon ecology.)

Environmental Assessment:

This is held by Adur District Council and available for examination by the public. Not on display at the public exhibition.

Information from Mike Turville (Environment Agency)

Except for my comments and surmise in brackets.

My Comment:

(The pipeline has a potential to alter the ecology of the lagoon, possibly for the worse*.  The main point is the new influx of small fish, crabs etc will reduce the existing fauna by competition and they will all die at the onset of winter with the fall in salinity. Raised salinity and water levels may also change the colour of the Glasswort, prevent  plants growing on the shingle banks on the Widewater flood plain, reduced the Lagoon Cockle population by crab predation, wipe out the rare hydroid if the Sticklebacks have not already done so, reduce Ringed Plover nesting sites etc. )

* This might not be right. Widewater Lagoon contains essentially marine fauna and these lagoons may rely on recruitment from the open sea to maintain some populations? Lagoons without a direct sea inlet may eventually become impoverished (arguable?).

Public Comment:

The public seem mostly concerned about raising the water level when it gets too low in the summer, so the lagoon does not become too smelly (hydrogen sulphide).
(I would have thought this would actually increase the flood risk by breaching in September storms, but this may not be important as the idea is to stop any breaching in the first place, and if a major breach occurred this extra water in the lagoon would be insignificant.)

Widewater Lagoon
Brackish.htm
Glasswort
glasswort.htm

Cheers

Andy Horton
Glaucus@hotmail.com
Adur Valley Nature Notes
Adur2002.htm

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