Winter 2002

History of Tidal Flooding in Sefton

Article by Tony Smith

The Sefton Coast is like a sand castle that is easily washed away by the sea. Because it has no outcrops of rock the forces of nature readily mould it, so the shoreline is constantly changing in response to the influence of wind and water and as a result of human activity. Before the construction of coastal defences the sea sometimes broke through the sand dunes and flooded low-lying inland areas. However people moved with and adapted to changes in the position of the coast. The geological evidence of such events can be found but there were few written records until recent times. Sixteenth century court proceedings mention the villages of Meanedale, Argameols and Ravemmeols lost to the sea and old maps show a village of Altmouth near what is now the Altcar Rifle Range.

Nicholas Blundell's diary describes "great losses sustained in Lancashire in December 1720 by the violent overflowing of the sea". Storm tides had flooded 6,600 acres of land, washed down 157 houses, and damaged 200 more. The main areas of damage were on low-lying land at Pilling Moss and Marton Moss near the Fylde Coast and the West Lancashire Moss between Formby and Tarleton. At Ince Blundell sea banks were breached, the River Alt floodgates were broken and more than 100 acres of productive farmland were damaged by seawater. Roads and bridges were also affected, including a public bridge in Great Crosby known as 'Foremost poole bridge' (Far Moss Pool bridge).

When Southport was developed as a bathing resort in the early 19th century landowners built sea walls and the first promenade. Bland's 'Annals of Southport' relate how storms broke down these new sea walls in January 1839, December 1852 and January 1859. In October 1883 storms damaged the promenade extension and the Cheshire Lines Railway, which was under construction near the seafront. Greater damage occurred at Hesketh Bank in December 1833 and November 1866 when the sea bust through earth banks and flooded parts of the village and large areas of farmland.

During the 19th century, despite these storms the local coastline generally gained land because more sand was moved onshore during periods of favourable weather than was eroded by winter storms. In the 20th century this trend reversed around the exposed coast of Formby Point. The change was probably caused by an increase in the number of storms and the effects of navigation works in the Ribble and Mersey estuaries. The erosion rate is greatest at the boundary between the Formby National Trust and the Ainsdale National Nature Reserve, with an average loss of approximately 10ft (3m) per year over the past 100 years.

At Crosby the River Alt changed its course during the early 20th century. Having previously discharged seaward from Altcar in a westerly direction, it moved to the south and began to erode the coastline at Blundellsands. Seafront houses in Burbo Bank Road had to be abandoned as the land was slowly carried away despite attempts at artificial hardening. The River Alt was finally brought under control in 1936 by the construction of a training bank north of Hall Road that directed the flow seaward and away from the coastline. The coastline was reinstated and hardened by the tipping of demolition waste, builders' rubble and tin slag from local smelting factories. Crosby sea wall and promenade were built in the 1970's forming the Marine Park and protecting property from Seaforth to Hall Road West. The coast north of Hall Road West is still vulnerable to erosion and the tipped material is slowly breaking down and spreading along the shore towards Hightown. A major Government-funded study is now in progress to identify the best options for the management of the coastal defences between Crosby and Formby.

Although storm damage along the Sefton Coast is frequent and inevitable, there are few recent instances of damage to homes. However during the night of 11th and 12th November 1977 severe storms coinciding with high tides overtopped coastal defences throughout Lancashire and Cumbria. At Southport the midnight tide rose by more than one and a half metres (5ft) above its predicted level and flooded 110 houses at Harrogate Way in Crossens. No one was physically injured but floodwater up to a metre deep caused considerable damage to property. It was found that water had overtopped a length of sea bank dating from the 1890's which was lower than the other sea walls at Southport. Elsewhere in Sefton the sand dunes eroded by up to 20 metres (60ft), promenades, coastal parks and sea walls were damaged and there was much wind damage to inland property. The bank at Crossens was raised and strengthened during the following year and has not been damaged since.