Coasts Flashcards
How do waves form
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.
Properties of constructive wave
Strong swash weak backwash
Low in height
Less frequent 6-9 per min
Properties of destructive waves
Strong backwash weak swash
High waves
More frequent 15 per min
What is Longshore drift
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.
How is headland formed
They are sections of cliffs which do not erode as easily as the rest of the coast as they are made of harder rock
What is a cliff
Vertical rock face along the coast
What is the shape of a cliff determined by?
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
What is a wave cut platform
A narrow flat area often seen at the bottom of the cliff.
How is a wave cut platform formed
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
How is a stack formed
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.
How is a stump formed
The stack will eroded at the base from waves and higher water. This causes the stack to collapse leaving a stump.
Which land forms are created by the process of deposition
Beaches and spits
What are beaches and how are they formed
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.
What is a spit and how is it formed
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.
What four conditions need to be meet for a spit to form
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
Why are coastal defences needed?
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.
Hard engineering methods
Sea walls
Groynes
Gabions
Evaluate sea wall
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.
Evaluate gryones
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
Evaluate gabions
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
Soft engineering methods
Beach nourishment
Managed retreat
Evaluate beach nourishment
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
Evaluate managed retreat
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
What ways did the government at Newcastle use to ensure coastal protection?
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.
