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Cost of shoring up cliff crumbling under homes could reach £12m
UP to £12m could be needed to shore up a crumbling Yorkshire coastline where residents live in fear of further landslips.
In August last year residents of Knipe Point at Cayton Bay south of Scarborough said they were living on a knife edge following the emergence of fresh cracks in the cliff.
A landslip led to the enforced demolition of three bungalows and residents said the ground was crumbling away daily.
A report by John Riby, the head of technical services for Scarborough Borough Council, discusses what engineering stabilisation measures might be taken and the various risks involved.
His report will be discussed by members of the council's Cabinet on Tuesday.
He says: "The landslide, although not as active in scale as in the recent past, is ongoing and further movement could occur.
"Existing assets which may be put at risk by a further cliff recession include a section of the A165 Filey Road and 56 bungalows at Knipe Point."
Last summer the Cayton Cliff Instability Study, costing 300,000, was carried out to establish what was triggering the coastal landslide, decide on the risks to property and investigate what stabilisation measures might be appropriate.
Mr Riby says the investigation, paid for from a variety of
sources, "has confirmed, with a high degree of confidence, that Cayton Cliffs comprises a deep-seated translational landslide system.
"The origin of the landslide system is not known but believed to be many thousands of years old. The key landslide mechanisms affecting the site have been found to be:
"A deep confined natural groundwater table which has the potential to generate excess porewater pressures at the basal shear surface;
"Analysis of potential groundwater scenarios has indicated that only a modest rise in the upper water table is required to destabilise the shallow mudslide mechanisms of failure which are responsible for the ongoing failure/cliff top recession at Knipe Point."
The four landslide stabilisation measures considered in the report have all significant limitations and would cost anything from a minimum of 50,000 to a "prohibitive" 12m with no guarantee of success.
Mr Riby's preferred options for stabilising the sit e are:
"Installation of deep drainage to reduce and control groundwater levels in the deeper water table;
"Construction of spaced or contiguous concrete bored piles at Knipe Point to isolate the lower Cayton Cliff landslide system from the land above the headscarp."
However, he says: "It should be pointed out that notwithstanding that the council has taken advice in this matter and attracted grant aid for the site investigation there is no guarantee/commitment that further grant aid will be forthcoming, or that a cost effective and environmentally acceptable scheme can be developed and undertaken."
Whatever measures are deemed necessary other bodies will have to be consulted. These include the National Trust which owns the land and North Yorkshire County Council and the Environment Agency.
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Weather for Yorkshire
Tuesday 07 February 2012
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Sunny spells
Temperature: -8 C to 2 C
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