Managing a coastline - for the benefit of man and wildlife
Coastal processes mean that our term ‘coastline’ is a bit of an anachronism. The ‘coast’ is anything but a ‘line’. Everyday – twice a day – it changes, as the tide rises and falls. To think of the coastline as static does it a disservice.
There are situations and locations where this dynamic state forces change onto an area of land that has, up to that point, been defended from the sea. A storm may breach a sea wall, for instance, flooding the land behind it.
Alternatively, though, a positive decision can be made to allow the sea to breach the defence in such a location. In fact, the breach can be man-made on behalf of the sea. This process is known as managed realignment.
But why – and where - would we choose to do that?
To answer the why: firstly, because it takes pressure of the remaining sea wall, prolonging its life as a defence. Secondly, because it allows a new habitat – saltmarsh – to develop behind the old, breached sea wall, and in front of a new sea wall, which is built further back inland. This saltmarsh in itself has immense value: not only is it a natural sea defence, but because each year, over 100 hectares of saltmarsh are lost in the UK alone.
Managed realignment comes out of an acceptance that working with natural coastal processes is far more effective in the long term than simply trying to ‘hold the line’, and build up a hard defence.
And where? Freiston Shore RSPB nature reserve is one such location where managed realignment has taken place for the benefit of both wildlife and people. The reserve, which came into being when the Environment Agency deliberately breached the old sea wall in summer 2002, lies on the Lincolnshire Wash coast, about four miles east of Boston.
Severe erosion was occurring on part of an outer sea bank at Freiston Shore. The opportunity for managed realignment to be used to overcome this – as well as the opportunity to establish a new nature reserve – was chosen as the way forward. First, the old inner bank was strengthened, after which then three breaches were cut in the eroding outer bank. The sea was therefore allowed to flood in to the 66 hectare area between the two banks.
Over time, saltmarsh has started to form in this area. It provides a defence, as well as a valuable habitat. We expect that eventually it will be able to support 40 pairs of nesting redshanks, skylarks and other typical saltmarsh birds. It should also be popular with feeding twites and dark-bellied brent geese in the winter.
But saltmarsh is not the only habitat created as a result of this process. Material required to build up the sea banks was taken from a ‘borrow area’ immediately adjacent to the sea banks. This area was then landscaped and a series of islands created. Finally the borrow area was linked to the sea, and has now become a saline lagoon.
Although this lagoon is not large (15 hectares), it is home to a significant number of nesting waders, including avocets and little ringed plovers. The lagoon has also become a high tide wader roost site, and a feeding/loafing area for wigeons, teals and dark-bellied brent geese. A bird hide overlooks the lagoon, providing a great spectacle for visitors. Overall, a wide range of bird species have been attracted to the reserve across a number of different habitats, proving that working with costal processes can have a positive impact for both man, and for wildlife.
John Badley RSPB Freiston Shore site manager