2B.5c

• why are coasts described as dynamic environments?

  coastal environments are continuously being shaped and reshaped. These change due to the interaction of winds, waves, currents and terrestrial and marine sediments. The processes and landforms are created as a result of energy and sediment e.g. storms, tsunamis, landslides, coastal management
• what is dynamic equilibrium?

  the balanced state of a system, where inputs and outputs balance over time
• the coastal system is driven by wave energy generated within the nearshore
• what are inputs + examples?

  material or energy moving into the system from outside e.g. precipitation or wind
• what are outputs + examples?

  material or energy moving from the system to the outside e.g. ocean currents, rip tides, sediment transfer and evaporation
• what is energy + examples of its effects?

  power of driving force e.g. energy associated with flowing water, movement of air - wind energy transferred to wave energy
• what are stores + examples?

  the individual elements or parts of a system that contain sediment e.g. beaches, sand dunes, and nearshore sediment
• example of dynamic equilibrium?

  constructive waves build up a beach, making it steeper. This encourages the formation of destructive waves that plunge rather than surge. Redistribution of sediment offshore by destructive waves reduces the beach gradient which encourages the waves to become more constructive. This is a constant dynamic equilibrium between the type of wave and the angle of the beach
• sediment cell: areas along the coastline and in the nearshore area where the movement of material is largely self-contained. It is a closed system -->no sediment is transferred between cells. The boundaries are determined by the topography and shape of the coastline
• large features like peninsulas, such as the Llyn Peninsula in Wales act as huge natural barriers that prevent the transfer of sediment. In reality, it's unlikely that the cells are fully closed, due to variations in wind direction and tidal currents --> some sediment is transferred. There are also some sub-shells within the major cells
• how many sediment cells are there in England and Wales?

  11
• source: places where sediment is generated - e.g. cliffs, eroding sand dunes, rivers, offshore bars
• transfers: places where sediement is transported from one place to another through LSD and offshore currents. e.g. beaches, salt marshes, sand dunes
• human intervention e.g. coastal management in the source region may reduce the sediment supply e.g. sea walls preventing cliff erosion
• sink: deposition e.g. spits and offshore bars
• dynamic equilibrium: sediment is constantly generated in the source region, transported through the transport region and deposited in the sink region. It's reached when the inputs of sediment from the source region are balanced by the amount being deposited in sinks
• negative feedback: when the change produced creates effects that operate to reduce or work against the original change e.g. when erosion leads to mass movement, the fallen sediment acts as a barrier protecting the cliff from erosion
• positive feedback: when the change produced creates effects that operate to increase the original change e.g. People walking over sand dunes destroys vegetation growing there and causes further erosion