The coastal questions in the 2021 Edexcel assessment materials

These are just the extended prose questions

2021 Edexcel Assessment exercises – A Level Coastal landscapes – 20 marks

SAMs

Evaluate the contribution that changes in sea level make to the formation of coastal landscapes. (20)

Coastal landscapes are the outcome of a variety of processes over a range of different time scales. Some erosional landscapes such as cliffs, arches and stacks are mostly the product of periods when sea levels have been constant. However, there are a series of landscapes which have been created by much more variation in sea level, sometimes by submergence, i.e. flooding, and sometimes as a result of emergence, when sea level falls.

Changes in sea level mostly result from the variations in the volume of water in the global oceans and are known as eustatic changes. These are caused by changes in global temperatures which affect the amount of water in the oceans. An increase in global temperature leads to higher rates of melting of ice stored on the land in ice sheets, ice caps and valley glaciers. As a consequence, there is a global increase in the volume of water in the ocean and a rise in sea level. When the sea level rose after the last Ice Age it formed a number of submerged or flooded landforms.

One submerged landform is a ria, which is a drowned river valley. The lowest part of the river’s course and the floodplains alongside the river become completely flooded. In cross section rias have an open V-shape with the valley sides quite gently sloping. In long profile they have a smooth course and water of fairly similar depth. When seen from above they tend to be winding, showing the original route of the river and its valley, formed by fluvial erosion in the river channel. There are lots of rias on the south-west coasts of Devon and Cornwall, for example at Salcombe and Fowey.

Another submerged landform is a fjord, which is a submerged glacial valley. Fjords have steep valley sides and the water is very deep. They have a U-shaped cross section because this was the original shape of the glacial valley. They tend to be much straighter than rias as the glacier would have truncated any interlocking spurs when it moved through the valley. The Sogne Fjord in Norway is 200 km long and over 1000m deep. The steep mountains around it are over 2,000m high.

Another landform created by rising sea level is a shingle beach. As sea level rose at the end of the last glacial period, wave action pushed marine sediments onshore, forming tombolos and bars. For example, the tombolo at Chesil Beach was formed from the sediment carried into the English Channel by meltwater during the glacial period and built up in Lyme Bay. As sea level rose, sediment was carried onshore by the south-westerly waves. It became attached to the Isle of Portland at one end and the mainland at Abbotsbury at the other.

In contrast, some landscapes are created by emergence. Over the last 10,000 years, land in the NW of Scotland has been rising, and hence sea level falling, as a result of isostatic change. This occurs when the extra weight of ice on the land is released by the melting of the ice, causing the land to readjust upwards relative to the local sea level. This has created landscapes of emergence with fossil caves, beaches, cliffs and even stacks left ‘high and dry’ above present-day sea level.

All of these landforms are affected by processes going on with present-day sea level and could also change in the future. Both rias and fjords are being altered by the waves currently acting on their sides and eroding them. With sea levels predicted to rise by a further 0.6 m in the next 100 years, water depth in rias and fjords will increase. Shingle beaches are especially at risk of modification. The tombolo at Chesil Beach has already been changed by present day longshore drift processes. So, it is true that changes in sea level make a huge contribution to the formation of coastal landscapes.

June 2018

Evaluate the view that hard engineering approaches to coastal management produce more winners than losers. (20)

Hard engineering is a form of coastal management that involves the construction of man-made features to try to withstand the erosional impact of the sea and its waves. It involves the use of sea walls, groynes, rip rap armour and revetments. Whilst the winners are almost always going to be the immediate places protected by these features, there are inevitably longer-term consequences for other places indirectly affected that could be characterized as losers.

The village of Barmston on the Holderness coast, south of Flamborough Head in east Yorkshire, has experienced rapid rates of erosion due to the fact that the land is made up of boulder clay. On average the coastline is receding at a rate of 2m a year. This has resulted in the loss of farmland and holiday homes. It was thought necessary to introduce a hard management scheme because of the caravan site above the cliff. It has already lost land to the sea and the council thought it necessary to protect the tourism aspect of the area. The management used is rip rap armour at the base of the cliff. Drainage of the soft cliff face was also put in place.

The rip rap placed at the base of the cliff aims to stop such rapid rates of erosion as the boulders will absorb most of the waves energy and acts as an artificial headland. The scheme aims to rapidly decrease the rate of erosion in order to protect the caravan site, an obvious ‘winner’. This management scheme means that people living north of the scheme will also benefit as the process of longshore drift is prevented and so beach material will build up to the north. Unfortunately, this will accelerate the erosion of the area to the south of the rip rap due to lack of protective material, an obvious ‘loser’.

Further south on the same coastline, the policy decision at Hornsea was to ‘hold the line’. The town has 8,500 people and contains a historic site, Southorpe medieval village, and the well-known Hornsea Mere, a local beauty spot and SSSI. Despite the huge costs involved – a loss to the tax payers of the rest of East Yorkshire - a large sea wall has been constructed, and the town can clearly be seen to be a ‘winner’.

Elsewhere, on the south coast of England, at Barton on Sea the coastline is part of Christchurch Bay, stretching for 17km. Further along the coastline, the major tourist attraction of Bournemouth beach employed measures to conserve the sand on the beach by using coastal management schemes like groynes. This starved Barton of sand as the longshore drift was no longer pushing sand down the coast. This caused increased rates of erosion, and also the coastline is now particularly susceptible to rotational slumping due to its geology and so the coastline is receding over 1m a year. In 1991 a sea revetment costing £4.5 million was put in place in the hope that this would finally reduce the receding coastline – a significant ‘cost’ to the people of the area.

In conclusion, it can be seen that hard engineering provides clear benefits to the people directly affected by the schemes – the winners – such as Barmston, Hornsea and Bournemouth. However, there are consequences for people who live and depend on the coast further along the coast, such as at Barton on Sea. And, as hard engineering schemes are expensive, all tax payers in an area can be classed as losers as they are paying the costs of construction. In some ways therefore the ‘losers’ may be more numerous than the ‘winners’.

June 2019

Evaluate the view that coastal flood risks are increasing mainly because of rising sea levels. (20)

Climate change is likely to increase the risk of coastal flooding in the future, but the degree of risk is uncertain. If global warming continues at the rate scientists at the IPCC expect towards 2100 then sea level might rise by 40–90 cm but this is a large range. In addition, sea level is rising due to land-based ice melting (Greenland, West Antarctica, valley glaciers) and thermal expansion due to rising ocean temperatures. The exact contribution of each in the future can’t be known, so the flood risk to coasts is uncertain.

However, there are other factors that could be more significant. Cities such as Miami, Dhaka and New York have large areas of low-lying land, which could easily be flooded by future sea level rise. In developed countries such as the USA and Netherlands it is likely that sea defences along the lines of the Dutch Delta Project will be built to protect people and property. Nevertheless, major storms like Hurricane Sandy in 2012 can overwhelm the best defences. Hurricane Sandy caused 220 deaths and $69 billion in property damage.

London and the Thames Estuary is another good example of the possible threat of flood risk due to rising sea levels. The area is low lying and so is at risk from spring tides and storm surges linked to depressions, which is why the Thames Barrier was built in 1982. London is also sinking due to isostatic adjustment by 1–2 mm per year.

Warming from climate change could increase the risk from storms and hurricanes as some research suggests they may become more frequent and/or higher magnitude. However, this is likely to affect places on tropical storm tracks the most e.g. Miami and Dhaka, and have the biggest impact in emerging and developing countries where preparedness and capacity to cope is lowest. Overall, in places like Dhaka the impact of a few major tropical storms could be much more devastating than a slow rise in sea level - as it might be possible to adapt to the latter.

As well as sea levels rising, there are some locations where subsidence is causing land levels to drop. This is a risk in mega-deltas like the Mekong, Ganges/ Brahmaputra and Mississippi. The combination of subsidence and rising sea levels could be very serious, but subsidence is more related to poor river management than it is to climate change.

One key risk is the rising population in many cities. For example, the population at risk from flooding in Kolkata increases by roughly 600% to 2070, and 130% in Miami. In low-income cities there is likely to be an increase in population density and a continued existence of slum housing - both are major risk factors. In all cities the value of property will increase so the economic losses will escalate.

Overall, there are several factors that influence coastal flood risk. There is uncertainty about both the scale and pace of future sea-level rise because predictions of future global warming are vague. A 20 cm rise may be manageable with flood defences but a 100 cm rise could be catastrophic in some developing-world locations that lack the finance to build complex, high cost flood defences. By 2070, even with no climate change, more people will be at risk in Dhaka because of subsidence and population increase. However, if sea levels did rise by 50 cm by 2070 and there was an increase in cyclone magnitude and frequency the risk for Dhaka would increase significantly due to climate change.

Autumn 2020

Evaluate the view that rates of coastal recession are largely controlled by geological factors. (20)

Coastal recession is determined by a range of factors within the coastal system, and geological factors are just one of them. Geological factors are likely to be more important in certain locations where weaker rocks, such as clays, are more available to the waves for erosion. They are more obvious, however, where these are in stark contrast to harder rocks such as chalk and granite.

The Isle of Purbeck is a peninsula on the south coast of England where geology greatly influences the coastline. Here the rocks run west to east and produce a very different type of coastline when they are parallel to the coastline than when they lie at right angles to it. The southern part of the coast shows a concordant coastline. Here the resistant Portland limestone forms cliffs, and these have protected the land behind from erosion, only allowing the sea to break through in a few places (the larger Worbarrow Bay and the smaller Lulworth Cove) to the clay behind. To the east, the rocks run at right angles to the coast (known as discordant), allowing the sea to penetrate along the weaker clays and gravels and produce large bays (Swanage Bay and Studland Bay) flanked by outstanding headlands (The Foreland and Peveril Point). Geology is clearly an important factor here.

Flamborough Head in East Yorkshire is a chalk headland area exhibiting classic features of coastal erosion. The area is dominated by chalk with softer boulder clay on the upper slopes. Chalk in northern England is harder than that in southern England due to higher calcite content. Some chalk deposits also contain varying amounts of flint, a secondary deposit which is very hard. The layers of chalk dip in a southerly direction at 4o; they are well jointed and criss-crossed by minor faulting – all the necessary ingredients for erosion. In Selwicks Bay, several zones of weakness have been eroded by the sea to create caves, arches, stacks and stumps.

The recent geological history of the area is also important. Pre-glacially the cliffs were only made out of chalk and were about half their present height. The sea eroded caves, arches and stacks and a wave-cut platform by the usual coastal erosion processes. After the Ice Age the whole of this area was covered by a deposit of boulder clay, masking the pre-existing features: the caves were plugged with boulder clay and the bays were in-filled. However, as the North Sea basin filled up with water after the end of the Ice Age and waves reappeared, they removed some of the boulder clay, to reveal many of the original erosional features.

So, in the two areas named, geological factors have largely controlled the rates of coastal retreat. However, other areas of the UK have more regular periods of large waves driven by strong prevailing southwesterly winds and for these, geology is probably less important. Also, many areas with large and wide beaches may resist coastal erosion as waves will lose energy as they pass over them. Finally, in many coastal towns and villages such as those in east Yorkshire and Norfolk, coastal recession is much reduced by hard engineering schemes such as sea walls and gabions. Coastal recession is therefore influenced by a number of factors, but only controlled by geology in certain locations.