This page considers erosion hotspots in the context of the glacially deposited coastline of East Yorkshire, the greater section of which is known as the Holderness coast.
A coastal erosion hotspot, otherwise written hot-spot or hot spot and very occasionally abbreviated to EHS, may be regarded as a location along a designated stretch of receding coast where cliff loss is reliably measured over a given time as being significantly above the average for that length of coast.
Any natural or human action that brings about a local reduction in beach level is almost certain to produce an erosion hotspot. Two processes can be observed to do this.
Different in origin, one static and the other dynamic, they sometimes act together.
1. terminal groyne effect
The construction of defences against the sea in order to reduce erosion invariably results in an increase in the rate of cliff loss downdrift of the installation. This is called the terminal groyne effect (TGE). Hotspots caused by the terminal groyne effect are associated with particular locations.
2. sediment segmentation
Material which forms the beach is called beach sediment, a broad term for sand of all grades, for shingle, pebbles, cobbles, and rocks. Sediment is gradually driven down the coast by the action of sea current and tides. It moves not as a whole but in segments, or bodies. Depletion of sediment as one body gives way to another allows waves to reach the base of the cliff more frequently and with greater energy, often creating erosion hotspots. These hotspots move, or migrate, at the same southward pace as that of the sediment.
Monitoring of East Yorkshire coastal erosion takes place at the cliff top, normally twice a year. By making use of collected data, it is possible to track erosion activity, including hotspots. Below are some examples.
The tables display cliff loss in metres. Cells are colour graded for all values above coastal average – the darker the fill the greater the erosion.
Tunstall to Withernsea
A further example of hotspot movement is captured in the table below.
The path of severe cliff loss is imprinted across twenty seasons (ten years) as it travels five kilometres from the now truncated Pastures Lane, Tunstall (Profile 79), across Sand-le-Mere (profiles 82 to 84) and Waxholme (profiles 86 to 87), to approach the Withernsea defences.
Evidence of the course of two other movements appear in the table. From a fixed point on the cliff top, high rates of recession are seen to occur in cycles.
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Pastures Lane. Once a link between the communities of Tunstall and Hilston, the route along the cliff top has disappeared within the last decade [6 May 2013].
Beach below Tunstall. Another characteristic hotspot scene. Here, an exposed clay platform is breaking up to form mudballs
[28 September 2013].
Sand-le-Mere. Site of the lost mere in the name (cf. Skipsea Withow
), this low lying section of coast is particularly vulnerable to the effects of erosion events [25 June 2013].
A volumetrically low sediment compartment at Withernsea north coincides with the arrival of an erosion cycle [20 November 2014].
Withernsea to Easington
The length of Holderness coast from Withernsea to Easington gas terminal contains within it a marked contrast in erosion activity.
At the northern end, the cliffs south of Withernsea are, for about four kilometres or so, subject to extreme erosion. Because of the number of extensions added to defences protecting the town from the sea – the most recent in 2005 – the section provides an excellent illustration of the terminal groyne effect (TGE pictures).
A little north of The Runnell, Holmpton, 18.84 metres were lost at Profile 99 through the summer of 2007, representing a record seasonal value for the East Yorkshire coast since comprehensive monitoring began. Other exceptionally large losses can be seen in the data.
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Conversely, the southern end of the same stretch of coast experiences very little recession over the span of the table. This part includes Dimlington High Land, another SSSI [video scan, 11th August 2014: .mov, .wmv, .mp4].
The thick, often contorted deposits of till are considered to be a push moraine, and the land is understood to have once risen even higher to the east before being consumed by the sea.
This section does of course experience loss over time but material released from the cliff by heavy erosion in the northern section seems to have offered some protection.
Cliff line north of The Runnell, Holmpton. A loss of 31.56 metres was recorded from autumn 2006 to spring 2008 [20th April 2013].
The cliffs become higher south of Holmpton and may for a period absorb some hotspot movement [20 April 2013].
An exposure of Basement Till
from two glaciations ago at Dimlington High Land [14 December 2016].
High sand ridge and deep runnel, part of an ord system
, passes Dimlington High Land [31 August 2013].
Hornsea to Aldbrough
Finally, an example of a data table prepared for an ongoing hotspot study.
Cells containing values represent the migrationary course of a dynamic erosion hotspot which is seen in the table to begin to the south of the Hornsea defence system, later to traverse the defences at Mappleton. Although the table uses data from the current monitoring profile system, readings from the previous erosion post arrangement allow migration to be tracked back further.
Hornsea and Mappleton are sites affected by the terminal groyne effect, which is responsible for potentially increasing the rate of erosion downdrift of impediments to beach movement and thereby activating a static hotspot. There is some suggestion in the table that incidents of cliff loss are more widespread for a couple of kilometres below (i.e. south of) Mappleton.
Unfilled cells denote that no loss is recorded. Cells in a pale blue fill mark the paths of two other hotspot migrations, one preceding and the other following the subject. For clarity, values are omitted.
Average annual loss at undefended cliffs for the coast as a whole over the fifteen year period 2003 to 2017 is 1.73 metres (approximately 0.56 metres for autumn and 1.17 metres for spring).
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Data helpful for hotspot tracking anywhere along the coast are available from the following sheets:
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Tracing paths of dynamic erosion hotspots over the longer term may be possible using the combined data set.
The above methodology and examples would indicate that it is possible to forecast where significant erosion is likely to be observed. Indeed, fieldwork regularly confirms this to be the case.
Limitations apply. Location of likely cliff loss can be projected, but not amount. In a low energy season, there may be no loss at all. On the other hand, a storm surge can involve any part of the coast.
In addition to influencing the degree of loss, a seasonís wind and wave activity will affect the pace at which erosion events move along the coast. Again, a low energy season might cause a temporary stall.
Tracking the movement of hotspots from cliff loss data requires little effort and is reasonably reliable, though it is not the only way. A more process-oriented approach, which considers the relationship between cliff loss and movement of beach sediment, is presented at the following link.
more on East Yorkshire coastal erosion
Page prepared by Brian Williams in September 2012. Last change October 2019.