Coasts Flashcards
Are coastal environments open or closed systems?
Open
What is dynamic equilibrium?
When there is a balance between the inputs and the outputs of the system.
What are some inputs into a coastal system? (4)
- Energy from waves, wind, tides and sea currents.
- Sediment.
- Geology of coastline.
- Sea level change.
What are components of a coastal system?
- Erosional landforms and landscapes.
- Depositional landforms and landscapes.
What are some outputs of a coastal system? (3)
- Dissipation of wave energy.
- Accumulation of sediment above the tidal limit.
- Sediment removed beyond local sediment cells.
What are antecedent conditions?
The previous conditions.
What provides most of the energy in a coastal system?
Breaking waves.
Do erosional coastlines have more of less energy than depositional coastlines?
More energy.
What is negative feedback and what is an example of it?
Negative feedback is when an action leads to something becoming less that it was before; this could be a good or a bad thing.
- A decrease in wave energy could lead to deposition of sediment offshore, further reducing wave energy.
What is positive feedback and what is an example of it?
Positive feedback is when an action leads to something becoming more than it was before; this could be a good or bad thing.
- An increase in wave energy could scour the seabed, deepening the water and allowing more energy to enter the location.
What is steady state equilibrium?
A situation where variations in energy and the morphological response do not deviate too far from the long-term average.
What is meta-stable equilibrium?
This exists when an environment switches from two or more states of equilibrium however usually will go back to the normal state of equilibrium.
What is the backshore?
The backshore is the area between the high water mark and the landward limit of marine activity. Changes normally take place here only during storm activity.
What is the foreshore?
The foreshore is the area lying between the high water mark and the low water mark. Is it the most important zone for marine processes in times that are not influenced by storm activity.
What is the inshore?
The inshore is the area between the low water mark and the point where the waves cease to have any influence on the land beneath them.
What is the offshore?
The offshore is the area beyond the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments.
What is the nearshore and what does it consist of?
The nearshore is the area extending seaward from the high water mark to the area where waves begin to break.
It includes the swash zone, surf zone and breaker zone.
What is the swash zone?
The swash zone is the area where a turbulent layer of water washes up the beach following the breaking of a wave.
What is the surf zone?
The surf zone is the area between the point where waves break, forming a foamy, bubbly surface, and where the waves then move up the beach as swash in the swash zone.
What is the breaker zone?
The breaker zone is the area where waves approaching the coastline begin to break, usually where the water depth is 5 to 10m.
How are cliffs and wave cut platforms formed?
- Cliffs form as the sea erodes the land. Over time, cliffs retreat due to the action of the waves and weathering.
- Weathering and wave erosion cause a notch to form at the HWM. This eventually develops into a cave.
- Rock above the cave becomes unstable and collapses.
- Wave cut platforms are flat surfaces left behind when a cliff is eroded.
How are simple spits formed?
- Longshore drift deposits material across the river mouth, leaving a bank of sand and shingle sticking into the sea.
- A stright spit that grows roughly parallel to the coast is a simple spit.
What is an example of a simple spit?
Spurn Point
How are compound spits formed?
- A recurved end may form due to changes in wind and wave direction.
- Several recurved ends may be abandoned. A spit that has multiple recurved ends from several periods of growth are compound spits.
How are sand dunes formed?
- Sand dunes are formed when sand deposited by longshore drift is moved up the beach by wind.
- Sand trapped by driftwood or berms is colonised by plants and grasses. The vegetation stabilises the sand and encourages more sand to accumulate there, forming embryo dunes.
- Over time, the oldest dunes migrate inland as newer embryo dunes are formed. These mature dunes can reach up to heights of up to 10m
Name an example of a sand dune.
Gibraltar Point
How are barrier beaches formed?
A barrier beach is usually formed as an extension to a spit.
Longshore drift moves sediment along the coastline until there is a change in the coastline.
A spit develops, usually in a bay and
once the spit develops across the whole bay, a barrier beach forms.
Barrier beaches are unlikely to form in estuaries as the outcoming force of freshwater will always keep part of the estuary clear.
Colonisation by vegetation can stabilise the barrier beach and trap further sediment keeping the barrier beach above sea even at high tide.
Depending upon the climate the landward side may be colonised by mangroves in the still lagoon, which adds further stability.
Where can barrier islands be found?
Horn Island, Mississippi
How are caves, arches and stacks formed?
- Some landforms are found in cliffs- cliff profile features.
- Weak areas in rock such as joints are eroded to form caves.
- Caves on opposite sides of a narrow headland may eventually join up to form an arch.
- When an arch collapses, it forms a stack.
How are beaches formed?
- Beaches form when constructive waves deposit sediment on the shore- these are a store.
- Shingle beaches are steep and narrow. They are made up of larger particles, which pile up at steep angles.
- Sand beaches, formed from smaller particles, are wide and fat.
How are bars and tombolos made?
- Bars are formed when a spit joins two headlands together. This can occur across a bay or river mouth.
- A lagoon forms behind the bar.
- Bars can also form off the coast when material moves towards the coast. These may remain partly submerged and are called offshore bars.
- A bar that connect the shore to an island is called a tombolo.
Name an example of a bar.
Slapton sands bar, Devon
Name an example of a place joined by a tombolo.
St Ninian’s Isle, Shetland Islands
What is the fastest eroding coastline in Europe?
Holderness
How long is the Holderness Coastline?
61km
What are most of the cliffs at the Holderness Coastline made of?
Glacial till
What is the rate of erosion at Great Cowden (Holderness)?
4m/ year
What type of mass movement is Holderness prone to?
Slumping when it is wet.
Water makes clay heavier and acts as a lubricant between particles, which makes it unstable.
What direction is longshore drift on the Holderness Coastline?
Southwards
Where is sediment deposited on the Holderness coastline?
Where the ocean current meets the outflow of the Humber River.
Example of a headland at the Holderness Coastline
Flamborough Head
Where are slumping cliffs found at the Holderness Coastline?
Around Atwick Sands
Example of a spit at the Holderness Coastline
Spurn Point
Where can sand dunes be found on the Holderness Coastline?
Around Spurn Point
How many villages have been lost over the past 1000 years at the Holderness Coastline?
30
How much has the Holderness coastline retreated over the past 2000 years?
4km
Name an environmental consequence of erosion at the Holderness Coastline?
Loss of Sites of Specific Scientific Interest (SSSIs) for example the lagoons near Easington provide habitats for birds.
Name an economic consequence of erosion at the Holderness Coastline?
Loss of infrastructure for example the gas terminal at Easington is only 25m from the cliff edge.
Name an social consequence of erosion at the Holderness Coastline?
Loss of settlements and livelihoods for example the village of Skipsea is at risk and 80000m2 of good quality farmland is lost each year on the Holderness coast, which has a huge effect on farmers’ livelihoods.
How much of the Holderness coast is protected by hard engineering?
11.4 km
What is Bridlington protected by?
4.7km long sea wall and timber groynes
What coastal defences are at Hornsea?
Concrete sea wall, timber groynes and riprap.
What coastal defences were built at Mappleton in 1991?
Two rock groynes and a 500m long revetment.
They cost £2 million and were built to protect the village and the B1242 coastal road.
What has a landowner is Skipsea used to protect his caravan park?
Gabions
What is Easington gas terminal protected by?
Revetment
Why has the Mappleton scheme negatively effected other areas?
Groynes have caused beaches to be sediment starved and so the cliffs southward of Mappleton are experiencing increased erosion.
Cowden Farm is at risk of falling into the sea.
What is a negative of bays being formed due to protection of local areas along the Holderness?
As bays develop the wave pressure on headlands will increase and eventually the cost of maintaining the sea defences may become too high.
Are existing schemes at the Holderness Coastline sustainable?
No
Who developed the ICZM for the Holderness Coastline?
East Riding of Yorkshire Council
What does the ICZM manage?
Complete sections of the coast as a whole
What was the ICZM used to develop?
The Flamborough Head to Gibraltar Point Shoreline Management Plan
What does the SMP for Holderness for the next 50 years suggest?
Holding the line at some settlements but doing nothing at less populated stretches.
Would managed realignment be more sustainable on the Holderness coastline?
Yes, however there are issues surrounding how much compensation businesses would get for relocating.
Relocating also isn’t always possible.
In 1995, what did the Holderness Borough Council decide to do?
Stop trying to protect Spurn Point from erosion and overwashing.
This saves money and allows the spit to function naturally but overwashing may damage marsh environments behind the spit.
A coastguard station on the spit may be at risk.
What does the SMP suggest in terms of Easington Gas Terminal?
To maintain the rock revetments for as long as the gas terminal is running.
The defences only span 1km meaning the village of Easington (pop 700) is not protected.
The defences may also increase erosion as SSSIs to the south.
Name an estuarine environment.
The Severn Estuary
How are waves created?
- As wind hits the water, ripples form. Then, wind gets an even better grip and continues to push the ripples until they grow into larger waves.
What does wind energy depend on?
Speed, distance and time
Features of constructive waves.
- Low wave frequency
- Low energy
- Strong swash
- Weak backwash
Features of destructuve waves.
- High wave frequency
- Weak swash
- High energy
- Strong backwash
- Small wavelength
What happens when a wave approaches a headland?
- They begin to slow due to the shallower water around the headland.
- However the waves which remain in deeper water continue to move faster towards the bay as they are unaffected by friction.
What is the highest and lowest point of a wave?
Trough- lowest
Crest- highest
What are rip tides?
- Strong narrow currents that flow seaward through the surf zone.
- Run along the surface of the water.
- Formed by a beaches topography.
- Beaches with breaking waves experience rip currents.
What are tides?
The periodic rise and fall in the level of the sea.
What causes tides?
The effect of gravity from the moon and the sun acting upon the rotating earth.
Ocean surfaces lift where the Earth’s gravity is slightly neutralised.
What is the ebb?
The tidal phase where the water level is falling.
What is the flood?
The tidal phase where the water is rising.
What is the tidal range?
The vertical difference in heighyt between consecutive high and low waters.
What causes a spring tide?
When the sun, moon and earth are in alignment.
What is a spring tide?
High tides are a little higher and low tides are a little lower than average.
What causes a neap tide?
When the moon faces the earth at a right angle to the sun so the gravitational force of the moon and sun work against each other.
What is a neap tide?
High tides are a little lower and low tides are a little higher than average.
What affects tides on a local scale?
Wind and weather patterns.
What are ocean currents?
The movement of water from one location to another.
What three factors drive ocean currents?
- Rise and fall of tides
- Wind
-Thermohaline circulation
How do currents affect the Earth’s climate?
They drive water from the equator and cold water from the poles around the Earth.
Name an area which uses tides to generate energy
Swansea Bay, Wales
Name a high energy coastline.
Portuguese west coast
Why does the portuguese west coast have a long fetch?
Fetch spans from northern tip of Brazil to Portuguese west coast.
Waves are generated along the fetch and are driven to the west coast due to the Gulf Stream.
The gulf steam divides into two- the North Atlantic Drift and Canary Current.