 |
  | ||||||
 Home
Coastal Heritage
Coastlines Magazine
Nature and Wildlife
Research
Sefton Coast Partnership
Shoreline Management
Students and Teachers
Visiting the Coast
| |||||||
|
Policies - Shoreline Management PlansAltcar to Birkdale Dune CoastlineSMP recommended policy:- Short term "Natural Defence Management" Long term "Natural Defence Management / Managed Retreat" The 16 kilometres of coast between the mouth of the River Alt at Hightown and Weld Road, Birkdale, is characterised by more than 30 square kilometres of sand dunes, with a maximum inland extent of 4 kilometres at Formby Point. Large areas of the sand have in the past been levelled for agricultural and residential development but, near the coast, the dunes reach up to 20 metres in height and form a barrier against marine incursion. The predominant source of the sand is the extensive sedimentary deposit in the eastern part of the Irish Sea. Tidal currents and prevailing weather patterns move the sand on to the beaches and into the river estuaries, from where, when dry, the sand is blown ashore to accumulate into dunes when conditions are favourable. There is evidence (Neil, 1993) of sand dunes on the Sefton coast for the past 3,500 years. Until recent centuries there was little human interference, the coastline was very mobile and the dunes were sometimes breached by storms or during periods of high sea level. In the early 18th Century, a series of storms caused extensive flooding of the south Lancashire coast and also stripped large amounts of sand from the dunes. The sand was carried inland and overwhelmed much of the agricultural land within two miles of the coast. This experience led to the early attempts at stabilisation and reclamation. The manorial landowners fostered the planting of "starr", or marram, grass and penalties were imposed for up-rooting the grass. These policies were successful during the 19th Century when, under favourable climatic conditions, the coastline around the whole area of Formby Point accreted seawards by approximately 300 metres. During the 19th Century more sand was moved onshore during periods of favourable weather than was eroded by winter storms. In the 20th Century this trend has been reversed. Evidence (Neil, 1993) suggests an increase in westerly storms around the turn of the Century. At about this time, the dredging and training works associated with the Ports of Liverpool and Preston were intensified, significantly changing the morphology of the offshore zone and increasing the degree to which wave energy is focused and reflected onto the coast north of Formby Point. During the 20th century almost all of the land gained at Formby in the 19th Century has been lost by erosion. At Altcar, to the south of Formby Point, the coastal bay formerly occupied by Formby Channel is accreting but around the whole area of Formby Point erosion proceeds at an average rate of up to 4.5 metres per year, depending on location. Accretion commences about a kilometre north of Ainsdale National Nature Reserve and remains the dominant trend at Southport and within the Ribble Estuary. The past development of the coastline has been examined, using maps and charts from 1700 to 1950, assisted by aerial photographs and coastal surveys from 1950 to the present date. Examination of the measurements taken over the past 30 years reveals that, despite the attempts at control, the rates of change are sufficiently consistent to enable a realistic projection to be made for the next 30 to 50 years. The following projection assumes that no major engineering works are undertaken to control the erosion and that the climate does not vary more than it has over the past 50 years. By the year 2050, the coastline between Sefton's Lifeboat Road car park and the National Trust Victoria Road car park is likely to erode by approximately 150 metres. North of Victoria Road, the coastline is likely to erode up to 270 metres along the Formby Golf Club frontage. The "hinges" between erosion and accretion, located approximately at the Formby/Ainsdale boundary (1200 metres north of Fishermans Path) and at Alexandra Road (600 metres south of Lifeboat Road), are unlikely to change significantly. This represents a total loss of 225 acres of land. Land loss of this order does not entail any risk of inland flooding or any threat to developed land or property. Nor would there be any such risk if the present rates of erosion doubled or the same trends were to continue for a further 50 years. Over such longer time scales, however, the position is not predictable. Changing river channels and the effects of offshore sand drift will gradually change the shape of the seabed, significantly affecting the patterns of energy dissipation. Climatic variation over longer periods will further alter conditions at the shoreline. Because of the mobile nature of this shoreline any attempt to "freeze" it in position would fail. A fixed sea wall would soon be undermined by the continued loss of sand from the shore. Any successful defences would have to limit wave and current energies so as to allow sediment to drop out of its water-borne suspension and rebuild beach levels. Under present national and European legislation, any proposals for new coastal defences must be subjected to tests of technical, economic and environmental viability. Any major civil engineering work would be very expensive so that its cost would far outweigh the benefits (in terms of land value) that would be gained. It could not therefore be economically justified and also the consequent changes to the natural environment would entail major loss of internationally recognised and protected habitat. Operational members of the Sefton Coast Steering Group have considered the information presented above. All agencies accept that the natural dynamics of the beaches and dunes must be respected. Erosion and sand mobility are key processes that help to sustain the rare habitats for which the Sefton Coast is internationally recognised. Because there is no imminent threat of flooding, any intervention must not stifle these natural processes but should rather seek to preserve habitats and maintain appropriate levels of public access. The Coast Management Scheme's Beach Management Plan will be routinely up-dated, after full Public and Council consultation, to take account of the latest predicted rates of erosion and accretion. Present beach and dune management measures recognise the likelihood of storm damage and have some resources for remedy built in. Where visitor pressures are high it is acceptable to confine public movement to boardwalks and paths and to fence vulnerable areas. The regular beach patrols and management visits tailor the work to suit particular sites and climatic conditions.
|
 |
