Coastal landscapes as systems

Coastal Landscapes as Systems - 1.1 

Interrelated objects comprising components (stores) and processes (links) connected to form working unit or unified whole. Landscapes store and transfer energy and material. 

Energy available: kinetic, potential or thermal. 

Energy enables geomorphic processes that shape  landscape 

Components of Open System:

Open systems means that energy&matter can be transferred from neighbouring systems as an input. Also transferred to neighbouring systems as an output. E.G input of fluvial sediment from a river when it deposits its load at the mouth when available energy decreases. 

A coastal system has:

• Inputs: energy and sediment brought into the landscape - kinetic energy from wind&waves, thermal energy from sun, and potential energy from position of material on slopes; material from marine deposition, weathering and mass movement from cliffs 
• Outputs: the loss of energy/ sediment from the landscape - marine&wind erosion from beaches&rock surfaces; evaporation 
• Throughputs: stores such as beach and nearshore sedimentaccumulations. Flows (transfers) such as movement of sediment along a beach by longshore drift 

System Feedback in Coastal Landscapes:

When systems inputs and outputs equal, reaches a state of equilibrium. Eg, when rate sediment is added to beach equals the rate sediment being removed from beach; beach therefore remain same size.  

When equilibrium disrupted, system undergoes self-regualtion and changes form to restore equilibrium. Known as dynamic equilibrium as system responds to disturbance - example of negative feedback. 

Sediment Cells:

Sediment cell stretch coastline and associated nearshore area where movement of sediment, sand and shingle is largely self-contained. Sediment cell regarded as a closed system, suggests no sediment transferred between cells. 

Eleven large sediment cells around coast England&Wales. Boundaries determined by topography and shape of coastline. Physical features such as Land’s end act as natural barriers prevent transfer sediment to adjacent cells. In reality, unlikely sediment cells are completely closed. With wind directions and presence of tidal currents, it is inevitable some sediment is transferred between cells. Also many sub-cells of smaller scale in major cells. 

Winds:

Source of energy for coastal erosion and sediment transport is wave action. Wave energy generated by frictional drag of winds moving across ocean surface. Higher wind speed and longer fetch means larger waves and more energy they possess. Onshore winds from sea towards land effective at driving waves towards coast. If winds blow at oblique angle towards coasts, resultant waves will approach obliquely and generate longshore drift. 

Wind is moving force, able to cause erosion, transportation and deposition. These aeolian processes contribute to shaping coastal landscapes. 

Waves:

Waves possess potential energy as result position above wave trough and kinetic energy caused by motion of water within wave. Moving waves do not move water forward but waves impart a circular motion to the individual water molecules. e.g. ball in sea, doesn’t move forward, only up/down. 

Energy is wave in deep water approximated by: P = H²T

P = power in kilowatts per metre of wave front 

H = wave height in metres 

T…