Coastal Systems and Landscapes

• closed system


  no inputs or outputs of matter but there can be inputs or output of energy
• open system


  inputs and outputs of both energy and matter e.g. coasts
• system components


  inputs -> processes/stores -> outputs -> positive/negative feedback -> inputs
• sources of energy


  winds, waves (constructive and destructive), currents, tides
• inputs


  energy sources, sediment, geology, sea level change
• processes which make changes in a system


  erosion and transport
• outputs


  dissipation of wave energy, accumulation of sediment above tidal limit, sediment removed beyond local sediment cells
• positive feedback


  the effects of an action are amplified by the subsequent knock on effects
• negative feedback


  effects of an action are cancelled out by subsequent knock on effects
• dynamic equilibrium


  where there is a balance between the inputs and the outputs
• coastal zone

  
• backshore


  area between high water mark and landward limit of marine activity. Changes normally only take place here in storm activity.
• foreshore


  the area between the high water mark and low water mark. It is the most important zone for marine processes in times that are not influenced by storm activity.
• inshore


  the area between the low water mark and the point where waves cease to have any influence on the land beneath them
• offshore


  the area beyond the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments
• nearshore


  the area extending seaward from the high water mark to the area where waves begin to break
• swash zone


  area in the nearshore where a turbulent layer of water washes up the beach following the breaking of a wave
• surf zone


  area in the nearshore 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
• breaker zone


  are ain the nearshore where waves approaching the coastline begin to break, usually where the water depth is 5-10m
• outline an example of positive feedback in a coastal system
• other examples of feedback in a coastal system
• erosion


  wearing away of the Earth's surface by the mechanical action of process of glaciers, rivers, marine waves and wind.
• fetch


  the distance of open water over which a wind blows uninterrupted by major land obstacles. The length of fetch helps to determine the magnitude and energy of the waves reaching the coast.
• mass movement


  the movement of material downhill under the influence of gravity, but may also be assisted by rainfall
• weathering


  the breakdown and/or decay of rock at or near the Earth's surface creating regolith that remains in situ until its removed by later erosional processes. Weathering can be physical, chemical or biological.
• wind as a source of energy


  the winds speed will determine wave energy contributing to more erosion/deposition, wave energy is also determined by the fetch and wind duration. The wind causes frictional drag on the water to create waves. The wind can also cause erosion (abrasion) by picking up fine materials such as sand and scraping them along surfaces.
• wave features


  amplitude (crest to trough), wavelength (crest to crest), wave period (number of wavelengths in one minute)
• how do waves break


  as waves approach shallow water, friction with the seabed increases and the base of the wave begins to slow down. This has the effect of increasing the height and steepness of the wave until the upper part plunges forward and the wave breaks onto the shore.
• constructive waves


  low amplitude, long wavelength, low frequency (6-8/min), more powerful swash than backwash, depositional (formation of berms)
• destructive waves


  high amplitude, short wavelength, high frequency (10-14/min), stronger backwash than swash, erosional (storm beach where shingle is flung towards rear of beach)
• wave refraction


  as each wave approaches the coast, it tends to drag in the shallow water which meets the headland. This increases the wave height and wave steepness and shortens the wavelength. That part of the wave in deeper water moves faster, causing the wave to bend. As a result, higher energy waves hit the headland and erode it whilst low energy waves deposit sediment into bays to build up beaches.
• current


  permanent or seasonal movement of surface water in the seas and oceans
• longshore currents


  occur as most waves hit the coastline at an angle generating a flow of water (current) running parallel to the shoreline. This not only moves water along the surf zone but also transports sediment parallel to the shoreline.
• rip currents


  strong currents moving away from the shoreline. They develop when seawater is piled up along the coastline by incoming waves. Initially the current may run parallel to the coast before flowing out through the breaker zone, possibly at a headland or where the coast changes direction. These can be extremely hazardous.
• upwelling


  the movement of cold water from deep in the ocean towards the surface. The more dense cold water replaces the warmer surface water and creates nutrient-rich cold ocean currents. These currents form part of the pattern of global circulation currents.
• longshore drift


  where waves approach the shore at an angle and swash and backwash then transport material along the coast in the direction of prevailing wind and waves.
• tides


  the periodic rise and fall of the level of the sea in response to the gravitational pull of the sun and moon
• why does the moon has a greater gravitational pull than the sun


  the moon is closer to the earth than the sun is
• high tide


  the moons gravitational pull brings the water towards it and there is a compensatory bulge on the opposite side of the earth
• spring tide


  where the sun and the moon are aligned causing the highest tides (twice in a lunar month)