East Yorkshire coastal erosion

cliffs

Created by Brian Williams in December 2011.
Extended in October 2012.
Supplement to the erosion in pictures page.




 cliffs-0 (1000x666).jpg
A ‘buttress’ formation [Hilston : 29 September 2012].



Hover over image for location and date or see enlargements.

it’s not only the sea

Erosion of the glacial tills of Holderness is easily and rightly attributed to the action of the sea. But that's not the complete picture. Prolonged periods of wet weather, such as experienced in 2012, can also be a major agent of cliff erosion.

[1, 2] Saturated cliffs collapse in a wet slump.
[3] Mud flow.
[4] Rainwater seeps from under the weathered soil surface.
[5] A wet slump has created a mid-cliff cavity
[6] When lumpy or blocky material slips down a wet cliff face it may leave a slide path.


 Atwick: 30 April 2012
 Atwick: 30 April 2012
 Atwick: 30 April 2012
 Skipsea, Southfield Lane, 26 May 2012
 East Newton, 5 May 2012
 Out Newton, 12 May 2012
1
2
3
4
5
6

After the rains, the dry-out begins. Desiccation is the second part of erosion-by-rain. A walk along the beach on a warm day after a wet period will usually be accompanied by the recurrent sound of fine material trickling down the cliff – with perhaps a sudden fall of heavier material. Winds, for example the cold easterlies that blew during spring 2013, also dry the cliffs.

[7] The bottom of a slide path cracks and breaks up as it dries and shrinks.
[8] View down a drying wet slump.
[9] A surface made smooth by slipped material or wave-rounding may harden in the sun, though it too cracks.
[10] An example of ‘exfoliation’.


 Mappleton, 26 May 2012
 Holmpton: 12 May 2012
 Mappleton, 26 May 2012
 Easington north: 15 October 2011
7
8
9
10

at the cliff foot

Most of the time, however, coastal erosion is certainly the result of the sea eating away at the base of the cliff.

[11] Downdrift (ie. south) of a major defence work, the cliff line will curve sharply inland to create a bay. This is sometimes called the terminal groyne effect. In the right of the picture, a rock armour revetment lies parallel to the water line. An increased rate of erosion has ‘outflanked’ the defences. Undercutting is evident in the process.
[12] Close-up of the tide at the foot of a cliff.
[13] A wave-cut notch may appear above a ledge or platform.
[14] Well-defined cliff ‘toe’.
[15] Inclined platform.
[16] Raised wave-cut features like this sand step are indicative of a reduction of beach level, as when the beach itself is being eroded.


 Mappleton, 26 May 2012
 Ulrome, 10 June 2012
 Atwick: 5 August 2011
 Withernsea south: 24 September 2011
 Dimlington: 24 September 2011
 Easington north: 15 October 2011
11
12
13
14
15
16

Water action produces some unusual shapes at and around the cliff foot.

[17] Pendent lobe.
[18] ‘Monster’s foot’.
[19] Waves break around a ‘hog's head’ profile.


 Easington north: 15 October 2011
 Atwick: 5 August 2011
 Out Newton: 12 May 2012
17
18
19

the cliff face

The Holderness cliffs continually change in detail even where there appears to be ragged uniformity over distance.

[20] A faulted slide.
[21] Lateral break.
[22] Recent blocky fall from a promontory.
[23] Lengthy sections erode to a serrated configuration.


 Skipsea Withow: 15 July 2012
 Rolston: 15 September 2012
 Hollym: 3 September 2012
 Hollym: 3 September 2012
20
21
22
23

Unusual shapes are not confined to the cliff foot.

[24] These ‘pantaloon legs’ were undoubtedly formed as a result of material being washed or falling away.
[25] A Mount Rushmore-like head and face may be discerned (with another directly behind?).


 Hilston: 29 September 2012
 Skipsea south: 26 May 2012
24
25

By way of a demonstration of solids being moved around within the clay, two small pieces of stone are shown in picture 26 as found. When both were removed and one inverted, they fitted perfectly together.


 Aldbrough north: 17 September 2012
 Aldbrough north: 17 September 2012
26
26a

[27] An erratic seems to defy gravity. Common alignment within the till of pebbles and stones, as seen in the picture, is a guide to the direction of glacial movement.
[28] A ‘stringer’ of crushed chalk.
[29] Delicate impression of a fossil shell in a lump of fine-grained sediment [the species awaits identification].
[30] A wellington boot, most assuredly a ‘false fossil’, would demonstrate a need for care in the interpretation of embedded objects.


 Atwick: 5 August 2011
 Easington north: 15 October 2011
 Mappleton: 26 May 2012
 Dimlington: 3 September 2012
27
28
29
30

rotational slide

Some cliff collapse in clay material is regarded as conforming to a circular movement that can be mathematically described. One method calculates forces acting on notional vertical slices through the cliff.

A simpler approach is to consider the body of the cliff as pushing downwards, under the effect of gravity, while the foot of the cliff is free to move outwards. Groundwater increases weight in addition to adding a degree of fluidity to the clay and lubricating any internal movement. At the same time, the foot of the cliff may be weakened by undercutting and material removal.

 rotational slide

Slippage tends to follow an arc of rotation having a theoretical centre positioned forward of the cliff and above it. There could be more than one arc of rotation present in a collapse. An arc need not include the full height of the cliff since the clay will break wherever resistance is least – material from a previous collapse may be providing temporary protection at beach level.

[31] The most obvious visual characteristic of a rotational slide is a backwards tilt to the section descending the cliff.
[32] Reverse tilt is clearly evident above this wet slump.
[33] A pinnacle cluster descends with a marked landwards lean.
[35] Occasionally, an arc of rotation may be traced in the mind’s eye.


 Skipsea south: 16 April 2012
 East Newton: 5 May 2012
 Rolston: 15 September 2012
 Rolston: 15 September 2012
31
32
33
34

cavities

Hollows and voids, from dimples to caves, in the soft till are the result of a number of processes.

[35, 36] Taken close to each other at the same till boundary, the pictures suggest how a small space might start to enlarge.


 Dimlington: 3 September 2012
 Dimlington: 3 September 2012
35
36

[37] Clay platform exhibiting localised pitting.
[38] Horizontal crevices produced by sagging within the clay.
[39] A cavity above beach level.
[40] Cavities are formed at any angle to the beach line. The arrow points to the sea.
[41] Muliple cavity formation.
[42] It seems ironic that protective granite can break from a protective revetment, in this case at Withernsea, and become a potential agent of erosion as tides roll the rock pieces against the base of the cliff.

See also picture 5 above and erosion in pictures 7-10.


 Dimlington: 3 September 2012
 Hilston: 29 September 2012
 Withernsea south: 3 September 2012
 East Newton: 10 June 2012
 Aldbrough: 30 April 2012
 Withernsea south: 3 September 2012
37
38
39
40
41
42

on the cliff top

The cliff top is where social and economic consequences of coastal erosion are manifest. Plights of owners of domestic and holiday properties are well documented. Although quality agricultural land is removed each year, the costs of constructing defences are higher than the value of the loss. Also, protection for one locality is very likely to have a deleterious effect elsewhere.

[43] Farming of the continually reducing land asset is by necessity carried out to the edge.
[44] A late stage in the growing season can provide a clue to the extent of erosion since the crop was planted.
[45] Acquisition of land in the absence of defence works has to be for the shorter term.
[46] The same is true of commercial investment.
[47] Fly-tipping as an instance of environmental abuse.
[48] A tranquil pond about to be lost.


 Withernsea south: 3 September 2012
 Skipsea south: 5 August 2011
 Hilston: 17 September 2011
 Skipsea: 5 August 2011
 Tunstall: 24 September 2011
 Holmpton: 12 May 2012
43
44
45
46
47
48

[49] East Yorkshire’s coastal erosion is often represented by past measurement from the cliff edge...
[50] ...some markers being easier to spot than others.
[51] Pictures abound of roads that end abruptly...
[52] ...and tracks that lead off the edge.
[53] A route no longer available.


 Holmpton: 12 May 2012
 Holmpton: 12 May 2012
 Skipsea south: 16 April 2012
 Holmpton: 12 May 2012
 Hilston: 2 May 2010
49
50
51
52
53



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