When the wind blows over the sea, friction with the surface if the water causes ripples to form which develop into waves. They can also be caused by earthquakes or volcanic eruptions that shake the seabed (tsunamis).
2) What is Fetch?
The distance over which the wind has blown.
3) How do Waves Break?
When the waves reach the shore the seabed interrupts the circular movement of water. As the water becomes shallower, drag from the seafloor slows down the bottom of the wave, and the circular motion becomes more elliptical. This causes the crest (still going at its original speed) to rise up and eventually topple onto the beach.
4) What is the difference between swash and backwash?
The water rushing up to the beach is the swash, whereas the water flowing back towards the sea is the backwash.
5) Give 4 features of Constructive Waves
More powerful swash than backwash. Formed by distant storms (can be 100s of km away) Carry sediment so construct the beach. Waves are well-spaced apart.
6) Give 4 features of Destructive Waves
More powerful backwash than swash. Remove sediment and destroy the beach. Formed by local storms. They are closed spaced and often interfere with each other.
Land Processes that Shape the Coastline
1) What is Weathering?
The disintegration or decay of rocks in situ, largely caused by the weather and changes in ground temperature. There are three types: physical, chemical and biological.
2) What is Physical/Mechanical Weathering?
This involves the disintegration of rock without any chemical changes taking place. It often results in piles of scree at the bottom of bare, rocky outcrops.
3) What is Chemical Weathering?
Where a chemical change occurs when weathering takes place. Rainwater, being slightly acidic can dissolve certain rocks and minerals. Minerals and particles unaffected by chemical weathering are usually left as fine clay deposit.
4) What is Biological Weathering?
This involves the actions of flora and fauna. Plant roots are effective at growing and expanding in cracks in rocks. Rabbits can also burrow into weak rocks like sands.
5) What is Mass Movement?
The downhill movement of material under the influence of gravity. (Not in situ)
6) What are the Four Types of Mass Movement?
Rockfall, landslide, mudflow and rotational slip.
7) What is Rockfall?
Where fragments of rock break away from the rock face (and fall), often due to freeze-thaw weathering.
8) What is Landslide?
Where blocks of rock slide downhill.
9) What is Mudflow?
Where saturated soil and weak rock flows down a slope.
10) What is a Rotational Slip/Slump?
A slump of saturated soil and weak rock along a curved surface.
Marine Processes that Shape the Coastline
1) What are the Five Types of Coastal Erosion?
Hydraulic power, corrasion, abrasion, solution and attrition (ish)
2) What is Hydraulic Power?
The sheer power of waves as they smash onto a cliff. Trapped air is blasted into holes and cracks in the rock (cavitation), eventually causing the rock to break apart.
3) What is Corrasion?
This involves fragments of rock being picked up and hurled by the sea at a cliff. The rocks act like erosive tools by scraping and gouging at the cliff.
4) What is Abrasion?
The ‘sandpapering’ effect of pebbles grinding down a rocky surface, often causing it to become smooth.
5) What is Solution?
Some rocks like limestone and chalk are vulnerable to being dissolved by seawater.
6) What is Attrition?
Where rock fragments carried by the sea knock against each other, causing them to become smaller and more rounded.
7) What does Coastal Transportation Depend upon?
The size and quantity of sediment transported by the sea depends upon the strength of waves and tidal currents.
8) What are the Four Types of Coastal Transportation?
Solution, suspension, saltation and traction.
9) What is Solution?
Dissolved chemicals often derived from limestone or chalk.
10) What is Suspension?
Particles are suspended within the water.
11) What is Saltation?
A hopping or bouncing motion of pebbles too heavy to be suspended.
12) What is Traction?
Large pebbles rolled along the seabed.
13) What is the movement of sediment on a beach largely determined by?
The movement of sediment along the beach is largely determined by the direction of wave approach. When was approach ‘head on’, sediment is moved up and down the beach, with little lateral movement.
14) What happens when waves approach the beach at an angle?
Longshore drift (don’t we hate it!) If waves approach the beach at an angle (e.g. due to wind direction) sediment moves along the beach in a zig-zag pattern. The swash carries material up the beach at an angle, while the backwash then flows back towards the sea at 90 degrees.
15) When and Why does Coastal Deposition Occur?
It occurs in areas where the flow of water slows down. Sediment can no longer be carried or rolled along, so has to be deposited. Coastal deposition mainly occurs in bays, where wave energy is reduced upon entering the bay. This is why there are beaches in bays by not in headland.
Landforms from Erosion
1) Describe the Formation of Headlands and Bays
Headlands and bays are formed when rocks of different resistance are perpendicular to the sea. Less resistant rock is worn away to form a coastal inlet called a bay. Bays are more sheltered from the sea, as waves are less powerful and deposition usually dominates, so a sandy beach is a common feature of them. Resistant rock is eroded less, so jut out into the sea whilst their surroundings have been eroded. They are then most vulnerable to the power of the waves, which is why they often contain cliffs and wave-cut platforms.
2) How is a Wave-Cut Notch Formed?
A cliff is mainly eroded between the water level at high tide and at low tide. Erosion (like hydraulic power, abrasion and corrasion) undercuts the cliff to form a wave-cut notch.
3) How is a Wave-Cut Platform Formed from a Wave-Cut Notch?
Over a long period of time, the notch gets deeper until the overlying cliff can no longer support its weight and collapses. Through a continual sequence of wave-cut notches and cliff collapse, the cliff line retreats. In the cliff’s place will be a gently sloping, rocky platform called a wave-cut platform.
4) Describe a Wave-Cut Platform
They are typically quite smooth due to abrasion, but may be pockmarked with rockpools in some places. It may be covered with sand and shingle from long periods of constructive waves. But, destructive waves from local winter storms remove the beach, exposing the wave-cut platform once again.
5) How is a stump formed?
Lines of weakness in a headland, like joints or faults are especially vulnerable to erosion. Erosive processes like corrasion and hydraulic action gouge out the rock along the line of weakness to form a cave. Over time, erosion may lead to two back-to-back caves breaking through a headland, forming an arch. Gradually, the arch is enlarged by erosion at the base and sides by weathering processes acting on the roof. The roof eventually collapses to form an isolated pillar of rock, separate from the headland, known as a stack. This is then undercut and collapses to leave a stump, which is covered up at high tide.
Barton-on-Sea
1) Where is Barton-on-Sea?
Barton-on-Sea is located in Christchurch Bay in Hampshire.
2) Give some details about Cliff Collapse at Barton-on-Sea
It has long been affected by cliff collapse, having lost a number of buildings and a café. Despite extensive coastal defenses a fresh landslip occurred in 2008, and the houses of Barton Court are 20m from the cliff edge, and will likely be lost in the next 10 years.
3) Why are the Cliffs at Barton-on-Sea prone to collapse? (5)
The rocks are weak sands and clays, which are easily eroded by the sea and have little strength to resist collapse. The arrangement of rocks (permeable sands ontop of permeable clays) allows water to ‘pond up’ within the cliff, increasing their weight. This increases the pore water pressure within the cliffs and encourages collapse. The stretch of coastline faces the direct force of prevailing south-westernly winds. With a long fetch, the waves approaching Barton-on-Sea are powerful and can achieve up to 2m of erosion a year in places. Several chines or ‘Bunnies’ flow towards the coast, but then disappear into the permeable sands before they reach it, adding to the amount of water in the cliffs. Buildings on top of the cliffs increase the weight on the cliffs, making them more vulnerable to collapse and interfering with drainage.
Landforms from Deposition
1) What is a Beach?
The accumulation of sand and shingle found where deposition occurs at the coast.
2) How are Beaches Formed?
When waves enter a bay, they tend to bend to mirror the shape of the coast - wave refraction. This is caused by the waves getting shallower as they enter the bay. Wave refraction spreads out and reduces energy in a bay, which is why deposition occurs there.
3) Where are Sandy Beaches formed and when are Pebble Beaches formed?
Sandy beaches are often found in sheltered bays (bay head beaches). Pebble beaches usually form where cliffs are being eroded and where there are higher energy waves, such as along the south coast of the UK.
4) What are Berms?
Berms are small ridges in a beach that coincide with high-tide lines and storm lines. Some beaches may have several berms, each one representing a different tide level.
5) What is a Spit?
This is a narrow finger of sand or shingle jutting out into the sea from the land. They’re common across the world.
6) How is a Spit Formed?
As sediment is transported along the coast by longshore drift, it becomes deposited at a point where the coastline changes direction or a river mouth occurs. Gradually, as more and more sediment is deposited, the feature extends into the sea. Away from the coast, the tip is affected by waves approaching from different directions, and may become curved as a result. Over time, the sediment breaks the surface and a spit is formed. It soon becomes colonies by grass and bushes, and eventually trees will grow. On the landward, sheltered side where the water is calm, mudflats and salt marshes form - although these are close to sea level, so vulnerable to erosion, especially during storms.
8) How is a Bar Formed?
Occasionally, longshore drift may cause a spit to grow right across a bay, trapping a freshwater lake or lagoon behind it. This is a bar.
9) How is a Barrier Beach Formed?
In the UK, offshore bars have been driven onshore by rising sea levels following the ice melt at the end of the last glacial period about 10,000 years ago. This is called a barrier beach, e.g. Chesil Beach in Dorset.
7) Give some details about Hurst Castle Spit
Hurst Castle Spit is a shingle spit located on the Hampshire Coast close to the city of Southampton. The landform has been actively shaped by longshore drift for hundreds of years. Henry VIII built a castle near the tip of the spit to help defend England from possible invasions. The castle is now managed by English Heritage and is a popular tourist attraction.
Maldives
1) Where are the Maldives
The Maldives are a group of islands in the Indian Ocean, 199 of which are inhabited by about 300,000 people.
2) Why is the Maldives in Danger of Rising Sea Levels
The average island is 1.5m above sea level, but 80% of them are less the 1m above sea level. Because of this, scientists think they will be completely submerged in 50-100 years.
3) What would be the Economic Impacts of Rising Sea Levels
Tourism is the largest industry, 33% of GDP comes from it. If Velana International Airport (the main airport) is cannot function due to flooding, then the Maldives will be cut off from international tourists (more than 1 million in 2015) majorly reducing the country’s income. Fish processing plants may be damaged, reducing the Maldives’ fish exports, which currently produce 10% of GDP, also massively decreasing the country’s income.
4) What would be the Social Impacts of Rising Sea Levels
Houses could be damaged or destroyed, and severe flooding could make whole communities homeless. Supplies of freshwater are already low, and if they are polluted with seawater then even less will be available. People will have to rely on rainwater or build expensive desalination plants.
5) What would be the Environmental Impacts of Rising Sea Levels
Coastal flooding wears away beaches on the islands at a rapid rate. This destroys habitat and exposes the land behind to flooding. The soil on most islands is shallow (20cm or less) and this could be easily washed away by flooding, so most plants won’t be able to grow.
6) What would be the Political Impacts of Rising Sea Levels
Increased dependence on other governments, the Maldivian government had to ask the Japanese government for $60million to build a 3metre high sea wall to protect Malé, the capital. Environmental policies are changing as increased flooding is caused by rising sea level which is caused by global warming. The Maldivian Government has pledged to be carbon-neutral so it doesn’t contribute to this, and is trying to convince other governments to do the same. Long-term plans are also changing, and the government is considering buying land in countries like India and Australia and moving Maldivians there before their islands become uninhabitable.
Managing the Coastline
1) What is the Shoreline Management Plan?
The coastline of England and Wales has been divided up into self-contained sediment cells, and a shoreline management plan has been developed for each area. This details the natural processes, environmental considerations and human uses. Coastlines at risk from erosion or flooding have been identified and plans have been put in place to cope with the issues. But, mainly ‘holding the line’ has been decided, which is keeping the coastline where it is. However, planners occasionally decide to advance the line, giving the coastline more protection (e.g. by increasing the beach)
2) What does Hard Engineering Involve?
Hard Engineering involves using artificial structures to control the forces of nature. It has been used for many decades, but is less commonly used today as they are expensive, obtrusive, unnatural and have high maintenance costs.
3) How can Hard Engineering cause Destructive Knock-On Effects?
It can interfere with natural coastal processes, for example by altering wave patterns, erosion can become more concentrated farther down the coast, leading to cliff collapse.
4) What is a Sea Wall, and give some advantages and disadvantages of it?
A sea wall is a concrete or rock barrier placed at the foot of cliffs or the top of a beach. It has a curved face to reflect waves back and is usually 3-5m high. It is effective at stopping the sea and often has a walkway or promenade for people to walk along. But, it can be very obtrusive and unnatural to look at, and is very expensive (up to £6 million per km) and has high maintenance costs. Creates a stron backwash with erodes under the wall.
5) What are Groynes, and give some advantages and disadvantages of them?
Timber or rock structure built out to the sea from the coast. They trap sediment being moved by longshore drift - enlarging the coast. The longer beach acts as a buffer to the waves, reducing wave attack on the coast. The bigger beach can enhance tourist potential, they aren’t too expensive (10,000 at 200m intervals) and they can provide useful structures for those interested in fishing. But, in interrupting longshore drift, they starve beaches downdrift, often leading to increased rates of erosion elsewhere. The problem is only shifted. Groynes are unnatural.
6) What is Rock Armour, and give some advantages and disadvantages of it?
Piles of large boulders dumped at the foot of a cliff. They force waves to break, absorbing their energy and protecting the cliff. They are relatively cheap and easy to maintain (£1,000-4,000 per metre), and they can be used for fishing. But rocks are usually from other parts of the coastline, or even from abroad, so do not fit in with the local geology. And obtrusive.
7) What is Soft Engineering?
Tries to fit in and work with the natural coastal processes. It does not involve large artificial structures, and is often more ‘low key’ with low maintenance costs. Beach nourishment etc is more sustainable, so is usually the preferred option of coastal management.
8) What is Beach Nourishment and give advantages and disadvantages of it?
The addition of sand or shingle to a pre-existing beach to make it higher or broader. The sediment is obtained locally, so blends in with the existing beach material. It’s relatively cheap (£3,000 per metre), easy to maintain, blends in with the existing beach and increases tourist potential by blending in with the existing beach. But, it needs constant maintenance unless structures are built to retain the beach.
9) What is Dune Regeneration and give advantages and disadvantages of it?
Sand dunes are effective barriers to the sea, and marram grass can be planted to stabilise the dunes and help them develop. It maintains a natural environment that is popular with people and wildlife. Relatively cheap (£2,000 per 100 metres). But planting the grass and fencing off areas is time consuming, they can be easily damaged and destroyed, especially by trampling and storms.
10) What is Marsh Creation and give advantages and disadvantages of it?
Involves allowing low-lying coastal areas to be flooded by the sea to become salt marshes. They are effective barriers to the sea. It’s a form of managed retreat. It’s a cheaper option than maintaining sea defences protecting relatively low value land. (£5,000-10,000 per hectare) It creates a much needed habitat for wildlife. But, land will be lost as it is flooded and land owners will need to be compensated.
11) What is Managed Retreat?
Allowing some retreat of the coastline, and is an option if the land is relatively low value (like poor quality grazing land) or there is a high risk of flooding or cliff collapse. Cost-benefit analysis. It is likely to become an increasingly likely option with rising sea levels.
Minehead
1) Where is Minehead?
It’s on the north coast of Somerset, and is one of the region’s premier tourist resorts, home to a large Butlin’s and is visited by thousands of tourists every year.
2) Why are Coastal Defences Necessary at Minehead?
It was clear by the early 1990s that the contemporary sea defences would be inadequate, and that storm damage was estimated to be £21 million if nothing were done. So the Environment Agency developed a plan to defend the town and improve the amenity value.
3) When did work start and finish and what did it cost?
Work started in 1997, and defences were officially opened in 2001. The total loss was £12.1 million, a considerable saving on the potential losses. They have been extremely successful as they protect the town from storms and high tides, and create an attractive beach environment.
4) What are the 5 new features?
A 0.6 metre high sea wall, with a curved front to reflect waves and deter people from walking on it. The landward side is faced with attractive red local sandstone. Rock armour at the base of the wall to dissipate some wave energy. Sand beach nourishment to build up the beach by 2m in height. This forces waves to break farther out to sea and provides an excellent beach for tourists. For rock groynes to retain the beach and hinder longshore drift. A wide walkway with a seating area along the sea wall, popular with locals and tourists.
Salt Marshes
1) What are Salt Marshes?
Salt marshes are areas of periodically flooded low-lying wetlands. They are often rich in plants, birds and animals.
2) Describe Vegetation Succession in a Salt Marsh
A salt marsh begins life as an accumulation of mud and silt in the sheltered part of the coastline, e.g. in the lee of a spit or bar. As more deposition takes places, the mud begins to break the surface to form mudflats. Salt-tolerant plants such as cordgrass soon start to colonise the mudflats - early colonisers are known as pioneer plants. As the level of mud rises, it is less frequently covered by water. The conditions become less harsh as rainwater begins to wash out some of the salt, and decomposing plant matter improves the fertility of the new forming soil. New plants such as sea asters and sea lavender begin to colonies the area, and gradually, after hundreds of years trees grow and a succession of plants develops, (vegetation succession).
3) Why is Cordgrass a good Pioneer Plant?
It’s tolerant of salt water and its long roots prevent it from being swept away by waves and tides, as well as helping to trap sediment and stabilise the mud.
Keyhaven Marshes
1) Where are the Keyhaven Marshes?
Salt marshes formed in the lee of Hurst Castle Spit in Hampshire, close to Southampton.
2) Name 6 things that live in the marshes
Cordgrass (spiky, grows on mudflats), sea lavender (colourful flowers, attracts wildlife - like the Common Blue Butterfly, which lives on the marshes. Oystercatchers feed and nest on the marshes, and ringed plovers feed intertidally and nest there. Wold Spiders cling for hours on the submerged stems of cordgrass waiting for low tide and food.
3) Give 4 Threats to the Spit
The salt marsh is retreating by 6m each year, possibly due to it being squeezed between the low sea wall and rising sea levels (6mm per year). It’s under threat from the breaching of Hurst Castle Spit by severe storms. 50-80m eroded when the spit was eroded during the December 1989 storms. Increased demand for leisure and tourism has led to an increased number of visitors.
4) How are they Trying to make it Sustainable?
In 1996 rock armour and beach nourishment (£5 million) were used to increase the height and width of the spit and it has not been breached since. It has been nationally recognised as an important site for wildfowl and wading birds, so is an SSI and parts are a nature reserve. This means the area is carefully monitored and managed to maintain its rich diversity. Access is limited and development restricted.