The BGS Landslide Response Team received reports of two landslides on the east side of Whitby, North Yorkshire, following above average rainfall that affected most of the UK from April–November 2012.
On 28 November 2012, the media reported a landslide affecting a row of cottages on Aelfleda Terrace resulting in the demolition of five 100-year-old former jet workers' cottages.
On 29 November, additional movement was reported farther round the headland above Henrietta Street threatening the 140-year-old kipper smokehouse below.
As well as threatening homes and businesses below, cracks were reported to have appeared at the top of the cliff near St Mary's Church.
The BGS Landslide Response Team carried out a survey of the landslide on Henrietta Street, including a LiDAR survey, on 10 December 2012.
Data collected from this survey is logged in the BGS National Landslide Database NLD ID 18838/1.
The landslide had developed over the two weeks prior to our survey and had deposited debris at the rear of the cottages below the cliff. The smokehouse had been evacuated and some other properties were also empty.
The laser scan was undertaken from a roadside location on Henrietta Street opposite a small car park. It was not possible to access other vantage points due to obstruction by buildings and restrictions imposed by the local authority. It was noted that two sheds (or outbuildings) behind the smokehouse had apparently been displaced by the fallen debris.
Observations showed that drainage may have been instrumental in the failure; drains were visible in the cliff face and some drainage pipes had also fallen.
There was seepage from beneath the prominent sandstone layer (the Elller Beck Formation) and sloughing of the underlying mudstones.
Some large sandstone boulders were seen in a precarious position and likely to fall.
The depth of the landslide was not clear. However, a small scarp was observed at the cliff top. It was not clear whether this was part of the landslide or a separate shallow failure or alternatively recent excavations to remove dangerous material from the cliff.
The geology of this area of Whitby comprises the Alum Shale Member, at the bottom of the cliffs at beach level, overlain by the Dogger, Saltwick, Eller Beck and Cloughton Formations. Above this lies Devensian Till.
The Alum Shale Member of the Whitby Mudstone Formation (Lower Jurassic) is a grey claystone and siltstone and forms the beach platform and the base of the cliff in the east cliff of Whitby.
It is overlain by middle Jurassic sedimentary rocks comprising a 0.75 m thick ironstone (the Dogger Formation), which passes upwards to a fluviatile sequence of sandstones and mudstones of the Saltwick Formation.
Above this, the Eller Beck Formation comprises ironstone, sandstone and mudstone and, is in turn, overlain by the Cloughton Formation, a grey mudstone and siltstone with yellowish-grey sandstone.
The superficial glacial deposits at the top of the cliff comprise ‘till’ (formerly termed ‘boulder clay’) consisting of grey, brown and yellow clay with abundant rounded erratic pebbles and cobbles of various lithologies, including quartzite, sandstone, granite and chert; lenses of yellow-grey sand and pebbly sand are present locally.
The glacial deposits were laid down by the last (Late Devensian) ice-sheet.
Henrietta Street was previously known as the Haggerlythe and was a fashionable address with over 1000 residents. Its popularity was of short duration as several landslides occurred here:
In 1785 part of a battery, which had been erected beyond the sea end of the street, broke off from the cliff and fell into the sea; and at the same time a deep fissure was observed to run along behind the houses.
'At midnight, a strong new-built quay supporting a pile of buildings eighty feet above the margin of the sea, unable to sustain the pressure of the earth above, menaced approaching danger. The people had hardly time to escape with their clothes before it bowed and fell with a thundering crash followed by a large mass of earth, intermixed with stones of three to six tons in weight. Five houses more soon shared the same fate, torn from others which were left impending in different inclinations over the tremendous precipice. Next morning presented a most affecting scene — buildings parting from their adjoining ones forming rents from their roofs to their foundations several feet wide, others partly gone, leaving their unsupported walls and hanging rafters to follow; and to add to this distress, weighty portions of earth and stones began to descend from the high cliffe upon the houses situated at its foot. It was now dangerous to advance near; the back buildings were soon buried, and the front impelled towards the street overhanging their bases, and seeming to threaten the acceleration of those on the opposite side over the wasting rock ... one hundred and ninety-six families have been rendered destitute in this inclement season of the year, escaping half naked from the wreck without house, fire or food ... the feeling heart will easily imagine how distressing the appearance of numbers of the sick and dying must be, carried by their friends, only to expire in the first hospitable place that would afford them shelter'.
The Universal Magazine, 1787
'At last, in the night of Dec. 24, 1787, the expected catastrophe took place. A new-built staith gave way about midnight, and the buildings which it supported fell with a tremendous crash, followed by large masses of earth and stones, and shortly after by several of the adjacent houses. Next day, many of the buildings on the opposite side of the street were buried under vast loads of earth, which shot from the cliff above them; and as several of the other houses were so frightfully rent, shattered, or sunk, as to become uninhabitable, the extent of the calamity was very great. Fortunately no lives were lost, the inhabitants being alarmed by evident symptoms of the approaching overthrow; but there were many who saved almost nothing of their effects, having scarcely time to escape with their clothes, and no less than 196 families were deprived of their habitations. The doors of the humane were thrown open to the sufferers, and contributions were made for their relief; but the losses of some were too great to be thus repaired. Two individuals, Mr Charles Summerson and Mr John Ripley, lost, each of them, to the amount of £100 yearly rents. Many of the shattered houses were afterwards rebuilt; yet Henrietta street never wholly recovered from this violent shock: several buildings have since then been abandoned and taken down, and the upper part of the street has still a mutilated appearance.'
'A further serious landslip occurred on Wednesday, December 15th, 1870, the first indication on that occasion being the falling of plaster in the houses about eleven o'clock at night. An alarm was raised and people began to remove their goods, which soon littered the lower end of Henrietta Street and the top end of Church Street. The ground continued to move during the whole of the following day, and large fissures in the ground above gave evidence of greater destruction. Many thousands of tons of earth from the field between the church-yard and the sea fell on the scar. The top building of the street, Mr Harland's pipe factory, and his adjoining house, were soon a complete ruin. The Spa Ladder was lifted by outward pressure off the ground and its top end pointed skywards. In all a dozen houses were rendered untenable and families were rendered homeless.'
Scarborough Maritime Museum
'There was another movement in March 1923 where the whole of the ground between the topmost house in Henrietta Street and the Cliff beyond the Spa Ladder was affected. The Spa Ladder was irreparably damaged, and was held in position by the stout steel hawsers which anchored it to the cliff and to the East Pier. As the cliff was forced over the ironstone strata, a seam of cliff coal fell to the beach, and this was eagerly picked up, despite the risk from falling earth and stone.'
Scarborough Maritime Museum