Managed Retreat

Managed retreat (also known as managed realignment) has in the past involved a deliberate breaching, or removal, of existing coastal defences in order to allow the waters of adjacent coasts, estuaries or rivers to inundate the land behind. 

More recently managed retreat is listed as 'policy option' where it is no longer financially feasible to defend particular areas and breaching will occur naturally where existing sea defences are allowed to fail.

The Shoreline Management Plan guidance for England and Wales (issued in 2006) defines managed realignment as ‘the process of allowing the coast line to move backwards or forwards with management to control or limit that movement’.  This definition would additionally apply to activities such as sediment recharge which can be used extend the width of existing intertidal habitats.

This can only really work where population density is low and there is little infrastructure to protect. It is seen as being a much more sustainable way of the managing the coastline than using hard engineering methods. It can also be much cheaper than hard engineering projects.

Depending upon the height and shape of land behind the breached wall, there may or may not be a need to build a new line of defences behind the site. 

In most instances the newly flooded land is low-lying coastal flood plain and therefore a new seawall (or ‘counterwall’) is needed to clearly define the inundated area and protect the hinterland behind.  However, on areas with rising ground either no new line of defences or only a partial counterwall is required.

The Man sands managed retreat project in south devon is the culmination of several years of discussion to integrate a wetland conservation project with a managed retreat initiative.

The area which is owned by the National Trust is located approximately 1.5km south of Brixham on the South Devon coast. It is situated at the base of two steep sided coombes and is fed by two small streams, which run
through each of the valleys, across pasture land and then over a shingle bar and out to sea.

In 1985 the National Trust installed steel mesh gabions, two deep, along the whole of the beach, however, by 2001, it was obvious that these gabions were deteriorating due to sea action and vandalism. They were now presenting a health and safety issue and were regarded as an eyesore, leading the National Trust to reassess a future vision for the area. In addition there was a change in tenancy for the farmland behind the gabions and there were new opportunities to look at land management here.

Following consultation with local people, the Environment Agency, the local authority and the Parish Council, it was agreed to remove the sea defences and not replace them. This was done in January 2004 and has transformed the appearance of the beach in a very positive way.

The area behind the beach had historically been wetland and, it is thought, extended some distance up the valley. During the 1970s, the fields behind the beach were drained and when the Trust first acquired the site the whole valley was largely improved grassland with a few damp areas near the beach. This was intensively grazed with cattle and sheep and was subject to improvement with artificial fertilizer.

When the gabions were removed in 2004, a concrete drain which culveted the streams under the beach and out to sea was also removed, resulting in the flooding of the fields behind.

Initially, this produced a 2ha lake, or ley, which attracted considerable attention from birds and local birdwatchers, providing an attractive addition to the landscape and habitats of the area.

This lasted until March 2007 when the large freshwater ley disappeared in 2007 after the breach of the shingle bar. The ley attracted good numbers of wildfowl, waders and gulls and when it drained several birdwatchers were insistent that the National Trust should re-instate it. This created bad feeling locally and negative press, with individuals suggesting that other conservation bodies should manage the site and not the National Trust!

The main challenge has been to persuade local people that, with the sea defences not being replaced, the beach and its environs are to be part of a dynamic, evolving system and that, with climate change, it was going to be difficult to predict what the landscape will look like in the future.