Coastal Systems and Landscapes:

coastal system main inputs, outputs, flows/transfers and stores/components:

• inputs: sediment, energy input from wind waves and tides.

• outputs: sediment washed out or deposited.

• flows/transfers: erosion, weathering, transportation.

• stores/components: landforms, beaches, spits.

equilibrium in coastal systems:

• coast systems are generally in dynamic equilibrium - inputs and outputs are balanced

• a change in input our output can cause negative or positive feedback.

what is negative feedback?

when a change in the system causes other changes that have opposite effects. 

what is positive feedback?

when a change in the system causes other changes that have similar effect.

how is wind a source of energy?

• Winds are created by air moving from areas of high pressure to areas of low pressure. During events such as storms, the pressure gradient (the difference between high and low pressure) is high and winds can be very strong.

• Strong winds can generate powerful waves. In some areas, wind consistently blows from the same direction 

how is a wave created?

• Waves are created by the wind blowing over the surface of the sea.

• The friction between the wind and the surface of the sea gives the water a circular motion.

• The effect of a wave on the shore depends on its height. Wave height is affected by the wind speed and the fetch of the wave.

• The fetch is the maximum distance of sea the wind has blown over in creating the waves. 

• A high wind speed and a long fetch create higher and more powerful waves.

• As waves approach the shore they break. Friction with the sea bed slows the bottom of the waves and makes their motion more elliptical (squashed and oval-shaped). 

• The crest of the wave rises up and then collapses.

  Water washing up the beach is called the swash. Water washing back towards the sea is called the backwash

Constructive waves:

• low frequency 

• low and long whuch gives them a more elliptical cross profile 

• powerful swash carries material up beach and deposits it

Destructive waves:

• high and steep with a more circular cross profile 

• higher frequency 

• strong backwash removes material from beach

how does tides act as a source of energy in coastal systems?

• Tides are the periodic rise and fall of the ocean surface, caused by the gravitational pull of the Moon and the Sun.

• Tides affect the position at which waves break on the beach.

• The area of land between maximum high tide and minimum low tide is where most landforms are created and destroyed.

how do currents act as a source of energy in coastal systems?

• A current is the general flow of water in one direction - it can be caused by wind or by variations in water temperature and salinity.

• Currents move material along the coast.

High energy coasts:

• Recieve high inputs of energy from large powerful waves.

• Caused by strong winds, long fetches, steeply shelving offshore zones.

• High energy coastlines have sandy coves and rocky landforms

• The rate of erosion is often higher than rate of deposition

Low energy coasts:

• receive low inputs of energy from small gentle waves

• caused by gentle winds, short fetches, gently sloping offshore zones.

• some coastlines are low because there is a reef or island offshore protecting coast from full power of waves.

• Low energy coastlines often have saltmarshes and tidal mudflats.

• Rate of deposition is higher than the rate of erosion

Inputs of sediment in coastal systems:

• Rivers carry eroded sediment into the coastal system from inland

• Sediment is eroded from cliffs by waves, weathering and landslides.

• Sediment can be formed from the crushed shells of marine of organisms

what is a sediment budget?

the difference between the amount of sediment that enters the system and the amount that leaves

what is a positive sediment budget?

if more sediment enters the coastal system than leaves and overall the coastline builds outwards

• negative sediment budget: if more sediment leaves than enters the coastal system and overall the coastline retreats.

sediment cells:

• the coast is divided into sediment cells

• these are lengths of coastline that are entirely self-contained for the movement of sediment meaning that processes going in one cell doesn't affect the movement of sediment in another cell

• each cell is a closed system

Six main ways waves erode the coastline:

• Corrasion (bits of rock and sediment transported by the wave smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces)

• Hydraulic action (air cracks in cliffs is compressed when waves crash in. The pressure exerted by the compressed air breaks off rock pieces.)

• Cavitation (as waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off)

• Wave Quarrying (the energy of a wave as it breaks against a cliff is enough to detach bits of rocks).

• Solution (soluble rocks gradually dissolved by the seawater)

• Attrition (bits of rocks in the water smash against each other and break into smaller bits)

ways of transportation:

• solution

• suspension

• saltation

• traction

how is sediment transported along the shore:

• swash carries sediment up the beach, parallel to the prevailing wind.

• Backwash carries sediment back down the beach, at right angles.

• When there's an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along the shoreline

What is marine deposition?

When sediment carried by sea water is deposited

High energy coasts:

• Recieve high inputs of energy from large powerful waves.

• Caused by strong winds, long fetches, steeply shelving offshore zones.

• High energy coastlines have sandy coves and rocky landforms

• The rate of erosion is often higher than rate of deposition

What is aeolian deposition?

When sediment carried by wind is deposited

Why does marine and aeolian deposition happen?

• When the sediment load exceeds the ability of water or wind to carry it.

• This can be because sediment load increases or because wind flow slows down.