Coasts

Question 1

How do waves form

Answer 1

In open sea wind pulls on surface of water, causing water to rise
The water then rotates and returns to its starting point
When a wave reaches shallows friction effects the lower part slowing it down
This causes the higher part to keep going but be unsupported,
Causing it to form a crescent shape and topple.

Question 2

Properties of constructive wave

Answer 2

Strong swash weak backwash
Low in height
Less frequent 6-9 per min

Question 3

Properties of destructive waves

Answer 3

Strong backwash weak swash
High waves
More frequent 15 per min

Question 4

What is Longshore drift

Answer 4

LSD is when waves move material along the coast
The swash moves material up the beach at the angle of prevailing wind. The backwash moves it back towards sea at a 90° angle. This means the material moves along the beach.

Question 5

How is headland formed

Answer 5

They are sections of cliffs which do not erode as easily as the rest of the coast as they are made of harder rock

Question 6

What is a cliff

Answer 6

Vertical rock face along the coast

Question 7

What is the shape of a cliff determined by?

Answer 7

Determined by the nature of its geology, the type of rock the cliff is made from determines how resistant it is to erosion
The layers (strata) of the rock are angled can determine the shape of the cliff

Question 8

What is a wave cut platform

Answer 8

A narrow flat area often seen at the bottom of the cliff.

Question 9

How is a wave cut platform formed

Answer 9

Hydraulic action and abrasion erodes the face during high tide this attack at a certain area creates a notch. Eventually this notch expands and undercuts the cliff causing it to collapse leaving a platform at the level of lower water

Question 10

How is a stack formed

Answer 10

Hydraulic action and abrasion erode headland forming cracks on both sides.
Cracks widen to form caves on either side
Eventually these caves meet in the middle forming an arch
Arch becomes more eroded by hydraulic action abrasion and precipitation.
Arch collapses leaving a column of rock which stands separate from the headland this is called a stack.

Question 11

How is a stump formed

Answer 11

The stack will eroded at the base from waves and higher water. This causes the stack to collapse leaving a stump.

Question 12

Which land forms are created by the process of deposition

Answer 12

Beaches and spits

Question 13

What are beaches and how are they formed

Answer 13

Beaches are a coastal land form created by deposition.

They are formed in the intertidal area between high and low tide
Constructive waves push material onto the coast
The material can build up overtime and be blown in shore by wind
On sandy beaches the backwash can move the smaller particles creating a gentle slope
A shingle beach is steep as percolation occurs between larger particles, the energy of a wave is reduced so the backwash is not as powerful.

Question 14

What is a spit and how is it formed

Answer 14

Spits are a depositional landform that look like beaches and extend out from mainland into the sea

They occur because of LSD. When material transported reaches a natural break in the coastline, sand continues on, builds up and breaks through the surface.

Question 15

What four conditions need to be meet for a spit to form

Answer 15

Constant supply of sand or other material from erosion further up the coast
LSD operates most of the time
The coastline has a sudden change in direction to leave a sheltered Bay Area
The sea is quite shallow

Question 16

Why are coastal defences needed?

Answer 16

Economic importance
Ports are important for global trade and centres of commerce and investment
Tourism

People living on the coast
Many people live on the coastline so they need to protect homes

Biodiversity
The marsh areas around the coasts can breakdown waste and detoxification eg. reed beds in marsh can break down sewage and clean the water before it enters costal waters.

Question 17

Hard engineering methods

Answer 17

Sea walls
Groynes
Gabions

Question 18

Evaluate sea wall

Answer 18

Tall concrete walls built at the back of beaches
Curved shape to deflect erosive energy of wave

Can be economically acceptable if they are needed to protect many peoples properties
Prevents costal flooding

Expensive and need constant maintenance
May erode over time.

Question 19

Evaluate gryones

Answer 19

Catches sediment as it is moved along the beach by LSD this builds up the beach

Relatively cheaply and easily repaired (£5000 per metre)

Restricts movement of people along the beach

Accelerated erosion down shore of gryone and further along beach as LSD is interrupted

Question 20

Evaluate gabions

Answer 20

Metal cages filled with rocks
Waves crash against the rocks the energy is absorbed stoping the coastline form talking full force of erosion

Filled with local rocks so are cheap and sustainable

Metal rusts causing them to break open
Rats inhabit them
Not aesthetically pleasing

Question 21

Soft engineering methods

Answer 21

Beach nourishment
Managed retreat

Question 22

Evaluate beach nourishment

Answer 22

Sand or pebbles are deposited onto the beach to replenish it. Sand is dredged from the seabed

Cheaper than gryones (£3000 per sq. metre) and will be good for tourism.

Needs regular maintenance as sand not as tightly compacted so will erode faster

Question 23

Evaluate managed retreat

Answer 23

Coastline will be allowed to change naturally. People may be moved out and compensated for lost land.

Encouraged development of marshes and beaches which is good for environment

Not viable in every location

Question 24

What ways did the government at Newcastle use to ensure coastal protection?

Answer 24

Concrete Gryones- stopped sand getting to beaches further north like du drum bay

Rock armour- in the 1990s used on the royal County Down golf course and used along sections of dundrum bay. Controls erosion by dissipating the energy of storm waves.
Unsustainable as it reduces sediment for murlough bay and area of special scientific interest.

Sea wall- made in 2007, cost £4million. Hoped to last 50 years, protects built environment.
Refracted waves increase beach erosion not sustainable in the long term

Gaboions- used to protect recraeation grounds and protect recreation land and the mouth of river shimna. More sustainable than rock armour as the waters energy dissipates slowly. Cut off access to beach and aren’t very environmentally friendly.