The Holderness Coast
The Holderness Coast is one of Europe’s fastest eroding coastlines. The average annual rate of erosion is around 2 meters per year. The main reason for this is because the bedrock is made up of till. This material was deposited by glaciers over 18,000 years ago. The Holderness coast is a 61 km long stretch of low glacial drift cliffs 3m to 35m in height. They sweep in a smooth S shape from just south of Bridlington in the north to Spurn Point in the south. This smooth shape is only broken where sea defenses have reduced erosion at the protected point and increased it southwards. Contemporary evidence of rapid erosion is abundant. Military pillboxes built in 1940-41 lie at the cliff foot, roads end precipitously at the cliff edge and the local press regularly covers stories of properties falling into the sea.
Historical evidence is also abundant. Erosion has been rapid from at least the Roman era and dozens of villages and towns now lost to the sea are recorded. The coastline of Holderness is eroding at around 2m per year. The erosion occurs mainly during storms and tidal surges and a loss of 6m was recorded over two days at Barmston in October 1967. It is estimated that about 76,450,00 cubic meters of material have been lost from the Holderness coast in 100 years. Only 3% of this material is deposited at Spurn Point, the remainder is deposited in deeper water offshore or is carried across the mouth of the Humber to be deposited within the estuary itself or on the North Lincolnshire coast. Erosion increases as one moves southward.
The town of Bridlington at the northern extreme is protected by Flamborough Head to the north and the Smithic Sandbank which lies just offshore; this sandbank is 10 km long and at spring low water rises 2.7.m from the sea. South of this the 5 and 10 fathom (approx 10 and 20 meters) submarine contours lie close to the shore and there is no shelter from the maximum fetch across the North Sea from the northeast.
The cliffs are made up of loosely consolidated glacial till but there is no relationship between rates of erosion and type of till, nor with the height of the cliff.
There are several factors resulting in the Holderness coast suffering such rapid erosion. The first is that the Holderness plain is a former bay unfilled with easily eroded glacial tills. Waves undercutting the cliff produce slumping type landslips and the debris from these is easily swept away by the sea. A paleo-cliff runs from Sewer by on the south side of Flamborough Head to Hessle in the south and the sea is rapidly, in geological terms, cutting back to this pre-glacial shoreline.
R.G. Allinson-Winn (1904) showed that deep-sea erosion was occurring as well as cliff line erosion since the deep water has advanced over the sites of former cliff line villages. The submarine contours drop off rapidly offshore, at Dimlington High land in the south the 10m submarine contour is only 600m from the beach. he coast is thus subject to the full force of the waves from the North Sea with little attenuation before they reach the cliff line.
The chalk headland of Flamborough Head prevents transport of materials from the north by the dominant northeasterly waves. The resistant upper chalk, with very little flint produces a beach of rounded pebbles at Sewer by. These are easily destroyed by mechanical and solution action and decrease very rapidly in quantity southward. The result that little beach material is transported southward to the beaches of Holderness. The sea attempts to build up an equilibrium gradient by eroding the soft cliffs behind the beach, to which the strong waves have easy access.
Flamborough
Flamborough is the headland that forms the most northerly point of the Holderness Coast. The most striking aspect of Flamborough Head is the white chalk cliffs that surround it. The chalk lies in distinct horizontal layers, formed from the remains of tiny sea creatures millions of years ago. Above the chalk at the top of the cliffs is a layer of till (glacial deposits) left behind by glaciers 18,000 years ago, during the last Ice Age. As the cliffs below are worn away by the action of the waves, the clay soil often falls into the sea in huge landslips. The sea attacks the coast around the headland in two ways. Waves beat against the vertical cliffs and, at the high water line, weak points in the chalk are worn away into caves. The weakest points are where vertical cracks or fault lines have appeared in the horizontal beds of chalk. At places on the cliffs where the chalk juts out, these caves are worn away into rock arches. If the top of an arch collapses, the result is a pillar of chalk cut off from the rest of the headland – this is called a stack. Flamborough Head has many caves and arches, as well as a few stacks. The process of erosion that has created them can take hundreds of years to do its work.
Hornsea
A 2.9km stretch of shoreline fronts the town of Hornsea. It is a high density urban development containing residential and various tourist related properties. Hornsea’s local economy is dependent on tourism and recreation as well as incorporating a small fishing industry.
Hornsea lies upon unconsolidated till. This material was deposited by glaciers during the last ice age 18,000 years ago. The groins on Hornsea beach ensure wide and relatively steep beaches. The beach material is made up of sand and shingle. The position of the coastline at Hornsea has been artificially fixed since existing coastal defenses were erected in the early 1900s. Hard defenses in the form of a concrete seawall and timber groins afford protection and an on going refurbishment program ensure this has continued. More recently a stone gabion has been erected to the south of Hornsea. This helps protect the caravan park.
Beach material is being transported south along the Holderness Coast by longshore drift. In Hornsea sand has accumulated where protection exists. This is because the groins provide a barrier to sediment transportation. This has reduced erosion within the section but increased rates are evident further south.
Mappleton
Situated approximately 3km south of Hornsea lies the village of Mappleton. Supporting approximately 50 properties, the village has been subject to intense erosion at a rate of 2.0m per year, resulting in the access road being only 50m from the cliff edge at its closest point. Mappleton lies upon unconsolidated till. This material was deposited by glaciers during the last ice age 18,000 years ago. The two rock groins at Mappleton have helped develop wide and steep sandy beaches. In 1991 two rock groins and a rock revetment were built, as a consequence a substantial beach accumulated between the groins halting erosion. However, further south the rate of erosion has increased significantly. This is because material which is being carried south is not being replaced. It is trapped within the groins). Therefore there is no beach to protect the cliffs. Even during a neap tide, a tide which is 30% less than the average tidal range, the sea reaches the base of the soft cliffs and erosion occurs.
The Spurn
The area known as Spurn forms the southern extremity of the Holderness coast and includes the unique feature of Spurn Head, a sand and shingle spit 5.5km long, reaching across the mouth of the Humber. Spurn is made up of the material which has been transported along the Holderness Coast. This includes sand, sediment and shingle. Spurn Head is an example of a feature geographers call a spit. The spit forms a sweeping curve which continues the line of the coast. The sand which forms the spit has been transported along the Holderness Coast by longshore drift. The energy in the waves transporting the material reduces where the North Sea meets the Humber Estuary. As a result the material is deposited. This process is known as deposition.
Credit:ivythesis.typepad.com
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