A report on the landscape evolution of the Durham coast

Introduction and Background

This report aims to assess the landscape evolution of the Durham coast, and to determine the past, present and future processes acting on the coastline. Natural processes have shaped the region for millions of years, and at present the area is characterized by a number of physical features. These include Permian Magnesian Limestone Cliffs, glacial sediments, raised beaches, incised valleys and small coastal headlands. In the last 10,000 years the development of the costal zone has been in response to a switch from glacial to interglacial conditions, and the resultant rising global sea level.

However, over the last century increasing human activity has artificially modified the coastline in a number of ways. In the north east of England, coal mining was the dominant industry until the early 1990’s. Such activity was often characterized by the dumping of vast quantities of waste rock and low-grade coal onto the beaches by coastal mines (Humphries, 2001). The disturbances caused by active waste tipping to both the coastline and the natural ecosystems within the area were extensive: in some parts, the accumulations of waste reached 20m in thickness.

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That said, the decline of the coal industry throughout the 1980’s and its eventual closure allowed for a review of the management of the coastline. The result was the launch of the so-called ‘Turning the Tide’ project, which aimed to restore previous environmental conditions, as well as create new socio-economic opportunities (Wilkinson and McCay, 1998). The website explains how a small management team exists “to protect and enhance the special qualities of this unique coastline” (durhamheritagecoast.org). The project facilitated the removal of industrial waste, the development of recreational initiatives and the opening of coastal footpaths. Changes in both physical activities and anthropogenic attitudes towards the management of the coastline have allowed the area to redevelop.

We visited two sites, at Dawdon (a site popular for sea angling) and Whitburn, to execute a number of tasks in an attempt to understand these processes more, and to try and predict future changes. As such, I have divided this project into three separate categories: the past and long-term processes acting on the Durham coastline, present day activity in the region and our prediction of what may happen in the future. These categories will be followed by a discussion and conclusion.

Past and long-term processes acting on the Durham coastline: the long-term evolution of Dawdon Blast Beach and Whitburn

Bird (1984) makes the point that the evolution of coastlines can be analyzed in a number of ways: geological structure, marine processes, tidal conditions, changing sea levels and shifting climatic processes. By citing the number of influences that can play a role in the development of coastlines, Bird (1984) makes it clear that if we are to understand the present and future processes, we must first gain significant knowledge of the past. Therefore, in order to understand the Durham coastline completely, we must first look at the region’s historical geomorphology and its underlying geology.

Bridgland (1999) explains how the geology of Dawdon and Whitburn is primarily made up of Permian Magnesian Limestone. Above the limestone lies a layer of boulder clay, which supports grasslands, plant life and other wildlife. Going further back into time, though, reveals the influence of glaciation on the region’s geological development. Glacial deposits in the region reveal that ice was present until fifteen thousand years ago.

Britain’s glacial history is, in parts, incomplete and poorly understood. However, evidence in the form of glacial sediments, erratics, clast fabrics and striae can give us some understanding as to where the ice came from and how and why the sea-level has changed in the last 10,000 years. Erratics are simply rocks that have been transported and deposited by a previously existing glacier (Holden, 2005). Holden (2005: 528) also explains how “glacial abrasion causes striations” and the smoothing of some surfaces. The evidence for this is in present day striae, which were observed at Whitburn. Clastic fabric is composed of grains of rock, which have been weathered and eroded from previously existing bedrock (Holden, 2005). Transportation of clastic material is often by ice.

It is these separate forms of evidence that together suggest that the first glacial ice to appear in the region came from the northwest (Lunn, 1995). The second glacial ice witnessed is attributed to the Cheviot / Tweed area. It has been proven that Whitburn is located where previously different sections of ice may have competed against each other before eventually merging.Johnson (1995) also notes that further evidence of glacial activity in the region comes in the form of lakes, which are suggested to have formed during periods of deglaciation.

Shennan et. al (2006) have recently undertaken extensive research into relative sea level change, and attempted to reconstruct British ice sheets. Evidence suggests that the Durham coastline is still responding to the rising sea level and rapid changes of the last 10,000 years. Crucial to this area of study is the principle of isostasy, defined by Holden (2005:718) as “the principle by which the Earth’s crust floats upon the denser mantle.” Shennan et. al (2006) make it clear how relative sea level change, as a result of isostasy, depends not just on sea-level change but also land-level fluctuations. This is the principle of isostatic change.

The significance for past and long-term processes acting on the Durham coastline is that areas that were covered in ice, such as the northeast of England, are often still experiencing uplift as a result of their newfound buoyancy. The opposite is true of regions that were not covered in ice, such as southern England, which are currently subsiding. It is clear that the present day processes have been shaped by the geological history of the Durham coastline.

Present day processes

Dawdon Blast Beach is displayed in the appendix as figure 1. The pronounced headlands and bays that exist along the Durham coastline are the result of different rates of erosion. Erosion is occurring at Dawdon as the result of wave action and tidal currents: where the rock is more resistant headlands form, and where it is more easily eroded bays, like Dawdon Blast Beach, retreat inwards (Holden, 2005). Limestone, which, as previously said, is at the heart of the geology of the northeast coastline, is a rock that can produce extensive and defined erosional features. On land these are known as karst landscapes, but on the coast the erosion of limestone can often lead to the development of features such as stacks, stumps and arches. The impact of the sea is the cause of much unstableness along the coastline, providing sediment and other material for the water to transport and deposit elsewhere.

Indeed, the northeast coastline has little shelter from the impact of waves. But although erosion by wave action is commonly seen along the Durham coastline, the transportation and deposition of the eroded sediment along the coastline relies on other processes, too. This is because the headland and bay features reduce the impact of longshore drift. The direction of transportation is north to south, and much of the material is trapped by the headland at the south end of the bay. It appears that the transportation of sediment owes much of its existence to the power and direction of the wind, whereas the layout of the coastline, and in particular the existence of headlands, is the root of much deposition.

Some of the coastal features, though, are anthropogenic in nature: mining has influenced Dawdon Blast Beach in a number of ways over the last 100 years. The vast quantities of waste that was simply tipped onto the beach has affected habitats and ecosystems, discouraged visitors and left the local communities with little pride about their unique coastline (durhamheritagecoast.org). But the waste also raised the beach level and left many cliffs isolated from the sea. Evidence suggests that the mines were also responsible for the creation of a number of artificial lagoons as a result of their pumping out excess water below the natural sea level. The mining industry has had an ecological, environmental, social, economic and physical impact on Dawdon Blast Beach in the last 100 years.

Assessing erosion rates and predicting future change

The beach at Dawdon has been eroding at its northern end since the prevention of mine waste tipping. From 1994 onwards the beach has been monitored by the Environment Agency to assess erosion rates. In an attempt to predict any future change on the coastline, we used a leveling technique to construct our own profile of the Dawdon Blast Beach, before comparing it with the agency data from 1994 to 2010. Over a relatively short period of time (since 1994), the beach has suffered significant recession and sediment loss. Understanding the reason behind the erosion rates is an important factor in trying to determine any future changes.

Despite the closure of the mining industry some years ago, the legacy of the waste left on Dawdon Blast Beach continues today. The waste produced from the blast furnace and mining industry actually prevents heavy erosion to some parts of the cliff, acting as an artificial wall to the power of the sea and wind. However, as this waste is eventually removed (it is predicted to have completely gone within 15 years) the cliffs at Dawdon will become increasingly exposed to the influence of natural processes, and heavy erosion is predicted to occur. This will result in further inland retreat and lengthening of the bay.

As explained earlier, the process of longshore drift and sediment transportation travels from the north to the south along Dawdon Blast Beach. Like the waste, the deposited sediment acts as a temporary blockade and means that the southern end of the beach will remain protected for longer. As the sediment deposited by longshore drift reduces in quantity, further erosion is predicted to occur. Eventually, it will be necessary for anthropogenic intervention to prevent the coastline from being eroded too heavily. Human intervention may come in the form of sea barriers, or even in the introduction of sediment where it has been significantly removed.

Conclusion

This project has revealed how the Durham coast has been shaped throughout geological history, examined the modern day processes currently shaping it and made an attempt at predicting future erosion rates and development. It is clear that both natural and anthropogenic processes have had a significant influence on the development of the region. The current coastline and its landscape owe much of its existence to the historical glaciers and the force of the tides, both past and present. But this project has also revealed the extent to which human activity and production of waste have influenced natural geological development. The waste produced from the previously booming mines has impacted not only present day processes (ironically, it actually protected the cliffs from coastal erosion) but also what will happen in the future.

The closure of the mining industry, though, and the launch of the ‘Turning the Tide’ project means that there is more chance of the coastline re-discovering its natural state in the future. Now all that can be seen of the colliery are two structures adjacent to the car park, and the predicted removal of all the existing waste means that natural processes will once again assume their authority. Consequently, in the future we expect to see greater erosion rates than which currently exist. All of the processes and impacts that this project has investigated have had influence, positive on negative, on the development of the Durham coastal area, which has been and continues to be a cultural asset, important to the region’s economy, wellbeing and natural habitats.

References

1. Bird, E.C.F. 1984 ‘Coasts: an introduction to coastal geomorphology.’ Blackwell 3rd edition
2. Bridgland, D.R. 1999 ‘The Pleistocene Of North-East England.’ In: Bridgland, D.R., Horton, B.P. & Innes, J.B. (Eds). ‘The Quaternary Of North-East England.’ Field Guide, Quaternary Research Association, London, 1-9 www.durhamheritagecoast.org (accessed 8/4/2011)
3. Holden J, 2005, ‘An Introduction to Physical Geography and the Environment,’ Second Edition, Pearson Education Essex
4. Humphries, L. 2001. ‘A review of relative sea-level rise caused by mining-induced subsidence in the coastal zone: some implications for increased coastal recession.’ Climate Research 18, 147-156
5. Johnson, G., 1995: ‘Robson’s Geology of North East England.’ Transactions of the Natural History Society of Northumbria 56, part 5.
6. Lunn, A., 1995: ‘Quaternary.’ In: Johnson, G., 1995 (ed): ‘Robson’s Geology of North East England.’ Transactions of the Natural History Society of Northumbria 56, part 5, 297-312.
7. Shennan, I., Bradley, S., Milne, G., Brooks, A., Bassett, S. & Hamilton, S. 2006 ‘Relative sea-level changes, glacial isostatic modelling and ice-sheet reconstructions from the British Isles since the Last Glacial Maximum.’ Journal of Quaternary Science. 21:585-599
8. Wilkinson, D.L. and McCay, N.A.J. (1998). In Fox, H.R., Moore, H.M. and McIntosh, A.D. (eds) ‘Land Reclamation: Achieving Sustainable Benefits,’ Balkerna: Rotterdam

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