Coastal Erosion in East Anglia
The coastal areas of Norfolk and Suffolk are renowned for their rich history, beauty and natural diversity. There is however growing concern that many areas of the coastline are under threat from erosion and that the beaches, houses and nature reserves that are so plentiful in this area may soon be lost to the sea.
Many parts of the region have already suffered losses due to the intensification of coastal erosion. It is estimated that the sea is advancing onto undefended coastline by around 1 m each year, however some soft cliffs such as those at Kessingland and Covehithe are retreating at rates of up to 10 m each year, that is over 2.5 cm each day. Other examples of losses include the destruction of some of the coastal roads at Trimingham, Overstrand and Happisburgh. Coastal erosion has also resulted in losses to the bird colony at Winterton-on –Sea, which is a Site of Special Scientific Interest (SSSI) and the sensitive sand dune environment here is under threat. It is estimated that around 40% of former marshes in north Norfolk have disappeared, highlighting the large impact that coastal erosion is having on natural habitats and their associated flora and fauna. In Hemsby, 89 houses have been lost due to the encroachment of the sea and the site on which many of them stood up until 1984 is now underwater. Many recreational facilities and footpaths are also at risk, such as the golf courses at Brancaster and Holme.
Naturally beaches try to stay in a state of equilibrium so that the amount of material being deposited is equal to the amount of material being eroded. This was the state of most of the East Anglian coastline before the onset of severe coastal erosion. During winter, the dominance of onshore northerly winds resulted in the erosion of sand from beaches; this however was replenished during the summer with the help of offshore south-westerlies, thus maintaining a state of equilibrium.
There are numerous reasons why the problems of coastal erosion have been escalating. One reason is that East Anglian land is naturally sinking in relation to the sea at a rate of up to 1.5 mm a year in some areas. Coupled with sea level rise as a result of global warming, this has made our coastline much more vulnerable to erosive events. Global warming has not only led to sea level rise but has also resulted in changing weather patterns with a increase in the number of winter storms and strong northerly winds in the area; this is exactly the type of weather which results in increased beach erosion.
Many people believe that the extensive dredging off the East Anglian coast is also contributing to the loss of coastline. Aggregate dredging is thought to increase the problems of erosion through the removal of offshore sandbanks. Such sandbanks encourage breaking waves at sea, which means the sea has less energy when it reaches the shore and is therefore less erosive; it is argued that the removal of these sandbanks means that the bigger, more destructive waves are reaching the shoreline and stripping away the sand leaving steeper, stony beaches. In turn, steeper beaches increase water turbulence near the shore, which further erodes the beaches and effectively creates a 'wave barrier' that stops sand being deposited. In addition the natural state of steep beaches means that larger sediments are stable and sand is eroded away, the opposite is true for beaches with more shallow gradients.
While extensive research into the effects of offshore dredging continues so too does dredging activity in British waters with the UK being one of the biggest marine aggregate producers. Dredging licences are issued by the Crown Estate, who own the seabed up to a distance of 12 miles off the coast. .
There are presently 72 licences for dredging off the coast of Britain covering over 1500 km2 of seabed; a large proportion of this area is off the Norfolk and Suffolk coasts. Of the 20 million tonnes of material extracted each year, around half originates from East coast sites. Dredging of this sort began in East Anglia in 1973, when 3 million tonnes of material were removed, and has steadily grown ever since with nearly 10 million tonnes of material being removed in 2001.
The dredged material is used for construction, land reclamation and sea defences both within the UK and in Europe and there is a large demand for it. For example, 200,000 tonnes of sand is needed to build a mile of motorway and dredging restrictions in other European countries means that there is a constant need for British exports.
Dredged material is often used to replenish the eroded beaches in East Anglia. However, the effectiveness of such beach replenishment is questionable. Dredged material tends to be unconsolidated and is not sorted into different sizes in the way in which the sea naturally sorts material. This means that it is readily eroded away and returned to the sea, possibly back to the area it was dredged from originally. Other forms of sea defence also appear unable to offset the impact of increasing erosion. Although many areas with sea defences and walls, such as Felixstowe, are thought by the council to only have a low chance of flooding, there are numerous examples of coastal erosion in areas with traditional sea defences. For example, in Corton, erosion led to the loss of the defences and promenade in 2001. Beach erosion is also evident along many of the Felixstowe beaches and the pier faces possible demolition due to erosion of its footings. In October 2002, the foundations of numerous beach huts were destroyed and the sea also encroached under the road along a stretch of beach in Felixstowe, which is protected by groins and a sea wall.
A new sea defence strategy is alleged to overcome many of the problems of traditional sea defences and claims to have successfully alleviated and even reversed shoreline erosion along many of the badly eroded beaches of the Great Lakes. The technology consists of structures, which have been developed to imitate nature and encourage natural deposition of material on beaches. As the sea deposits the material, the problems associated with the unconsolidated material found on many beaches replenished by man are alleviated, thus making the beach inherently more stable. Over time, it is claimed that that the structures result in less sand being eroded away and as the beach grows it is able to hold on to arriving sand, thus neutralising the effects of erosion. These structures consist of rounded, concrete filled tubes, which are placed perpendicular to the shore, at about the same spacing as traditional groins. The structures taper down at the base and therefore do not affect longshore drift in the same way as traditional sea defences and consequently do not affect the sediment supply to beaches down current. The shape of these structures leads to a decrease in waves and turbulence and therefore creates lower energy beaches that are less prone to erosion. As more material is deposited, steeper beaches begin to flatten out and become more stable and sandy. This is the opposite to how many traditional structures work, their design results in near shore deepening and steeper beaches which in turn results in bigger waves and a continued cycle of erosion.
A combination of factors therefore appears to be driving the increased erosion along our coastlines, none of which can be easily resolved. In addition, the present defence mechanisms and strategies do not always appear to succeed in allaying these problems. There are no easy answers to such complex problems and there are numerous financial, ecological and social issues to consider in the development of a coastal protection plan. It is however clear that the problems of coastal erosion in East Anglia must continue to be addressed in order to minimise further damage to both our fragile coastal environment and the livelihoods and homes of the people who live there.