Coasts and coastal management

Question 1

What is hydraulic action?

Answer 1

Waves crash against the cliff, compressing the water and air into cracks and forcing the rocks apart.

Question 2

What is abrasion?

Answer 2

Waves pick up rocks from the sea bed or beach and smash them against the cliffs.

Question 3

What is corrosion?

Answer 3

Minerals such as calcium carbonate are slowly dissolved in sea water.

Question 4

What is attrition?

Answer 4

Sand and pebbles and picked up by the sea and smash against each other, wearing them down, into smaller rounded particles.

Question 5

How does the geology affect the shape of the coastline?

Answer 5

The softer less resistant rocks (sands and clays) are eroded more than the harder rocks. The softer rock is eroded by hydraulic action, where the force of the wave weakens the cliff. Rocks are then thrown at the cliff (abrasion) causing bits to break away. This leads to the formation of bays such as Swanage Bay. The harder rock is eroded more slowly causing it to jut out into the sea, creating headlands at Ballard Point and Durlston Head.

Question 6

How are stacks formed?

Answer 6

Would have started as a fault in the headland. Abrasion and hydraulic action would have eroded away at the fault causing a cave. The cave would get bigger until it formed an arch. After more years of erosion the arch roof would collapse forming a stack eg Old Harry. Eventually, the bottom will erode away and more a stump eg Old Harry’s Wife.

Question 7

How is a wave-cut platform formed?

Answer 7

The cliff face at the foot of the cliff by the sea if eroded by abrasion and hydraulic action. This forms a wave-cut notch at the foot of the cliff.
Once the wave cut notch is big enough the cliff above it collapses into the sea.
What is left behind is known as a wave-cut platform.

Question 8

What is weathering?

Answer 8

The on site break down of rock. This can also attack the cliff face along with erosion from the sea.

• freeze thaw
• onion weathering
• biological weathering
• carbonation

Question 9

What is freeze-thaw?

Answer 9

Water gets into cracks, freezes and expands breaking rocks.

Question 10

What is onion weathering?

Answer 10

Occurs in warm environments when rock is constantly heated and cooled causing it to crack.

Question 11

What is biological weathering?

Answer 11

Tree roots penetrating rock underneath ground.

Question 12

What is carbonation?

Answer 12

Rainwater dissolving rock (acid rain).

Question 13

What is a fetch?

Answer 13

The distance the wave has travelled before it reaches a coast.

Question 14

How does longshore drift occur?

Answer 14

The prevailing (dominant) wind pushed sediment up the beach via the swash. 
Gravity pulls the wave off of the beach, called backwash. 
In this way, sediment is moved along the beach. This is called longshore drift.

Question 15

What are sand dunes?

Answer 15

a dune is a mound of sand that is formed by the wind, usually along the beach or in a desert.

Question 16

What is the order of sand dunes?

Answer 16

Embryo dunes, fore dunes, yellow dunes, grey dunes, dune slack, dune slack.

Question 17

Why does the colour of the dune change?

Answer 17

Due to the amount of vegetation coverage.

Question 18

What is an embryo dune?

Answer 18

the sand is blown along the beach and is caught on an obstacle. The strand line is a pile of flotsam and jetsam( eg driftwood). Only special plants such as sea rocket can tolerate the salty conditions and grow here.

Question 19

What are mobile (yellow) dunes?

Answer 19

marram plants colonise which slows the air flow and causes more sand to be deposited.
The position of these dunes change because there are gaps between plants and when it is windy the sand is easily eroded on the windward side of each ridge. Them the sand is deposited on the leeward side where wind speeds are lower.

Question 20

What are fixed dunes?

Answer 20

the conditions for plants are less harsh and it is less windy with less salt spray. Therefore, they have a wide variety of plants. As there are more roots to bind to the soil there is less chance of the sand being eroded on windy days.

Question 21

What are dune slacks?

Answer 21

The rain soaks through the sandy ridges and comes to the surface in the dips between the ridges. Dune ridges are a habitat that may be flooded with fresh water during the winter months.

Question 22

What is zonation?

Answer 22

Distinctive bonds or zones of vegetation that stretch across the dunes.

Question 23

How has damage by vehicles been managed on sand dunes?

Answer 23

Sand posts to prevent cars driving into the dunes.
Built a wooden board across the dunes in 2 places to prevent further trampling and erosion.

Fencing had to be put up later to stop people walking through the dunes.

Question 24

How has dog fouling been managed on sand dunes?

Answer 24

People are not allowed to walk their dogs in the summer months.
The dogs foul does not bio-degrade due to the little bacteria.

Question 25

How has sand erosion due to visitors been managed on sand dunes?

Answer 25

Fencing off areas to prevent trampling. Planting more marram with signs to explain what they were doing. Created wind traps with brashings (branches and wire) which they though would encourage a layer of sand to be deposited. However, people walked around the fencing which created new trampled paths where nothing would grow. They removed the fences and accepted that sand erosion was a natural process.

Question 26

What is a destructive wave?

Answer 26

breaks beaches down | high wave, tail breaker, strong backwash, weak swash

Question 27

What is a constructive wave?

Answer 27

builds beaches up | low wave, weak backwash, strong swash.

Question 28

Where is Christchurch bay?

Answer 28

Bournemouth on the south coast of England. 140km SW of London.

Question 29

What is happening in Christchurch bay?

Answer 29

Losing 1-2 m of land each year (cliffs collapsing).

Question 30

How does rock formation lead to slumping at Barton on Sea?

Answer 30

there is permeable rock about impermeable rock. rain water infiltrates through the permeable layers and sits of the clay layer. the water builds up making the top layers heavier. this causes the clay layer to become slippery and results in the cliff slumping into the sea.

Question 31

What other factors are leading to erosion at Barton on Sea?

Answer 31

A boulder groyne at Hengistbury head traps sediment and prevents sediment from reaching Barton on Sea. So, waves hit the cliffs as there is less sand at Barton on Sea. Long fetch = powerful waves. Global warming and sea level rise.

Question 32

What is a recurved sea wall?

Answer 32

Concrete wall, curved under the side to deflect the power of the waves. Sea wall reflects rather than absorbing the wave energy. This is the most effective way of preventing erosion. Most expensive (up to 2.5 million pounds per km). Deflected waves often scour the base, under cutting the way which may cause it to collapse.

Question 33

What is rock armour? (or rip-rap)

Answer 33

Large boulders on the beach which reduces the force of the waves absorbing the wave energy within the gaps between the rocks. It is relatively cheap and uses natural materials/rocks. Environmentally ugly. They can be undercut and moved by waves due to washing away of sand beneath it.

Question 34

What are gabions?

Answer 34

Cages of boulders built into the cliff face - small rocks help absorb the energy. Effective where severe erosion occurs and it is cheaper than sea walls. They are environmentally ugly as they are usually used in large numbers the cost is approximately 350 pounds per metre.

Question 35

What is wooden revetment?

Answer 35

Wooden structure breaks the force of the waves and traps beach material behind them. They are much cheaper than a sea wall. They are effective at breaking the force of the waves. They are less durable than a sea wall so will need replacing quicker. They do not give total protection to the base of the cliff. Looks bad. Costs around 1000 pounds per metre.

Question 36

What are groynes?

Answer 36

Wooden, or sometimes steel structures, that stop long shore drift and build up/anchor the beach, protecting the base of the cliff. They stop long shore drift and encourage a build up of the beach. This is an effective way to reduce erosion. However, they increase erosion further down the coast by stopping long shore drift and starving areas down the coast of sediment. Cost = 5000-6000 pounds each.

Question 37

What is beach nourishment?

Answer 37

Build up the beach by replenishing beach material. This provides a natural solution to absorbing waves. Aesthetically better solution Can be expensive to keep transporting large amounts of sand - sediment moved by long shore drift so will need to be replaced. Works well with other defences.

Question 38

What are some causes of the Bangladesh flooding?

Answer 38

70% of Bangladesh is less than 1m above sea level. Experienced its heaviest rainfall in 50 year. Monsoon rainfall is concentrated into a few months. Deforestation has occurred in the Himalayas. Snow melt in the Himalayas. Silt is brought down by the river and raises river beds, decreasing the river capacity. Building on the floodplain increases run off. The Bay of Bengal is a funnel shape and gets shallower towards the coast.

Question 39

What are some impacts of the Bangladesh floods?

Answer 39

30 million people left homeless 600 people died as a direct result Damage to schools and hospitals put at 7 billion dollars. The main food crop, rice, was destroyed. Death toll rose to 750. Airports, roads and railways were flooded and bridges destroyed.

Question 40

What solutions were there for the Bangladesh floods?

Answer 40

Embankments have been built Flood shelters have been built and flood warning systems established Food supplies, medicines and blankets distributed. Water aid sought to provide water purification tablets. People have been encouraged to build their land on raised mounds of land. Flags raised to go to the shelter. Afforestation.

Question 41

What were some problems with the Bangladesh management strategies?

Answer 41

people brought their belongings to the shelter so there wasn't enough room. not everyone got the warnings. there weren't enough high up shelters. some people didn't listen to the warnings. there weren't enough shelters. the outdated system couldn't predict the path of the storms.

Question 42

Why were there floods in the North Sea?

Answer 42

Depressions. Depressions allow the sea level to rise creating a storm surge. As the depression is squeezed into the English Channel. This acts like a funnel pushing the sea level upwards. When combined with a spring tide, it causes an incredibly high storm surge.

Question 43

What are some of the impacts of the North Sea Floods?

Answer 43

``` 7 cliff homes collapses in Hemsby. 400 homes affected in the Humber region. 500 properties evacuated in Kent. Sea defences damaged. Homes without electricity in Scotland. 2 people in England died in 2013 floods. ```