3-1-1-landscapes-and-features-of-the-littoral-zone

Littoral Zone

The coast as a system

• As with any geographical system, the coast, as a system, has inputs, stores, transfers and outputs

• The system constantly strives to be in a state of dynamic equilibrium

• The coast can be viewed as both an open system and a closed system 

  • It is an open system because it receives inputs from the lithosphere, atmosphere, hydrosphere, biosphere and cryosphere

  • However, during research and coastline management the coast can be seen as a closed system where a specific sediment cell is examined

• There are examples of positive feedback at the coast

  • As waves erode the cliff, material is released

  • This material abrades the cliff which results in even more cliff erosion 

• There are also examples of negative feedback at the coast 

  • As the shore is eroded, the material makes the wave-cut platform wider

  • This can absorb wave energy and reduce the impact at the base of the cliff

The littoral zone

• The littoral zone is the area of the coast that can be affected by wave action

• It is a dynamic zone which means that it is constantly changing due to the interaction between processes on land and in the sea 

• These changes can be:

  • Long-term due to climate or sea level change

  • Short term due to the tides, waves, and storms

• It is divided into four zones:

  • Backshore is usually beyond the influence of wave action but can be affected during storm events

  • Foreshore is the intertidal area between high and low tide

  • Nearshore is the breaker zone where friction between the seabed and the waves causes them to break

  • Offshore is the area outside the influence of waves

Long Term Processes

• Coastal systems are affected by long term factors which include geology and changes in sea level 

Geology

• The geology is the characteristics of the land which includes both:

  • Rock type

  • Rock structure

• Coasts can be classified as:

  • Rocky

  • Sandy

  • Estuarine

• They can also be classified as: 

  • Concordant – where different rock types run parallel to the coast

  • Discordant – where different rock types run at right angles to the coast

Sea level change

• Sea level change can occur as a result of:

  • Global warming – natural and enhanced

  • Tectonic activity – which can lead sections of land to rise or subside

• Longer-term sea level change can be:

  • Eustatic – when the sea level itself changes 

  • Isostatic – when the land rises or falls relative to the sea

• This leads to coasts that are either emergent or submergent

Short Term Processes

• Coasts can also be categorised by short-term factors:

  • Waves – can be constructive or destructive

  • Tides – tidal range is the difference between high and low tide

  • Rivers

  • Storm events

• These create coastlines that can be:

  • Retreating or advancing which depends on whether erosion or deposition dominates

  • Dominated by land-based processes (primary coasts) or marine processes (secondary coasts)

  • Large or small tidal range 

  • High or low-energy 

Characteristics of High and Low Energy Coasts

Rocky Coasts

• Rocky coasts form where there is more resistant geology – in the UK this is mainly in the north and west of the country

• Cliffs of varying heights and steepness can be found along rocky coastlines:

  • Steep cliffs tend to be found in high energy environments

  • Cliffs with a gentler slope tend to be found in low energy environments

• Erosion is more dominant than deposition

• Two types of erosion may dominate along rocky coastlines:

  • Marine erosion – the action of waves

  • Sub-aerial erosion – weathering and mass movement

Coastal Plain Landscapes

• Coastal plains usually occur where the land gradually slopes down towards the sea

• Tend to be low relief

• Coastal plains include both:

  • Sandy coastlines

  • Estuarine coastlines

• These are usually low energy coastal environments

• They form due to coastal accretion – when deposition is greater than erosion

• Sediment for deposition comes from:

  • Offshore sources

  • Terrestrial sources

• Dunes form, helping to stabilise the coast and reduce erosion

• Wetlands and marshes form due to poor drainage

• Estuarine coastlines form at the mouths of rivers and are formed from clay and silt