Coast

• What is a system?

  a set of interrelated objects comprising of components (stores) and processes (links) that are connected together to form a working unit or unified whole
• Components of coastal system

  INPUTS - including kinetic energy from wind and waves, thermal energy from the heat of the Sun and potential energy from the position of material on slopes; material from marine deposition

  THROUGHPUTS - consists of stores and flows

  OUTPUTS - including marine and wind erosion from beaches, rock surfaces and evaporation
• When is a system equal?

  When a system's inputs and outputs are equal, a state of equilibrium exists
• What happens when equilibrium is disturbed?

  The system undergoes self-regulation and changes its form in order to restore equilibrium - dynamic equilibrium and negative feedback
• How many sediment cells are there in the UK?

  11
• How are boundaries defined in a sediment cell?


  Topography and shape of coastline
• Why is a sediment cell not a completely closed system?

  Due to variations in wind direction and presence fo tidal currents = some movement of material so are regarded as largely closed systems
• Where does energy come from for coastal erosion and sediment transport?

  Wave action which is generated by the frictional drag of winds moving across the ocean surface
• Relationship between wind speed and fetch

  Higher the wind speed, the longer the fetch so the more energy the waves possess
• How is longshore drift generated?

  If winds blow at an oblique angle to the coast, the resultant waves will also approach obliquely and generate LSD
• Do waves move forward?

  Waves do not move forward, but waves impart a circular motion to the individual water molecules
• What is the equation for energy in a wave?

  P = H2 x T, where P is power (kW/m), H is height (m) and T is time interval between crests (s)
• Characteristics of swell waves

  Swell waves have a long wavelength with a wave period of 20 seconds
• Characteristics of storm waves

  Storm waves have a short wave length, greater height and a shorter wave period
• Affect of friction of breaking waves

  Friction between the seafloor and the water profoundly changes the speed, direction and shape of the waves:

  - slow as they drag

  - wavelength decreases, successive waves bunch up

  - deepest part of the waves slows down more than the top

  - waves steepen
• 3 types of breaking waves

  spilling: steep waves break onto gently sloping beaches, plunging: kind of steep waves break onto steep beaches, surging: low-angle waves break onto steep beaches
• What happens to the speed of a wave as it travels up the beach?

  Speed of wave decreases due to friction
• What is backwash?


  The movement of water back down the beach
• Characteristics of constructive waves

  - Low in height

  - Long wavelength, low frequency

  - Spilling waves

  - Strong swag

  - Retains energy as not disrupted by breaking of another wave

  - Lots of percolation

  - Material moved onshore

  - SWASH EXCEEDS BACKWASH
• Characteristics of destructive waves

  - Greater in height

  - Short wavelength, higher frequency

  - Plunging waves - little forward energy

  - Swash is slowed by friction of meeting the backwash of a previous wave

  - Little percolation

  - Material deposited offshore

  - BACKWASH EXCEEDS SWASH
• Relationship between beach gradient and wave type

  - High-energy waves remove material and transport it offshore, reducing beach gradient

  - Low-energy waves, build up beach face, steepening the profile
• How is a high tide created?

  The Moon pulls water towards it, creating a high tide, and there is a compensatory bulge of the opposite side of the Earth - locations between the bulges will be at low tide

  
• When does a spring tide occur?

  When the Sun and the Moon are in alignment, occurs twice a lunar month
• When does a neap tide occur?

  Moon and Sun are at right angles to each other, gravitational pull is weakest, occurs twice a lunar month
• How does tidal range affect development of coastal landscapes?

  Tidal range influences where wave action occurs, the weathering processes that happen on land exposed between tides and the potential scouring effect of waves along coasts with a high tidal range
• Influence of rock structure on rock strata

  - Horizontally bedded and landward-dipping strata support cliffs with steep, vertical profiles

  - Seward-dipping strata tend to follow the angle of dip of the bedding planes
• Affect of rip currents of coastlines

  Play an important role in the transport of sediment - caused by either tidal motion or by waves breaking at right angles to the shore

  Rip currents modify the shore profile by creating cusps which help to perpetuate the rip current, channeling flow through a narrow neck (small scale)
• What are ocean currents?

  Masses of ocean water that flow from one place to another, much larger scale and are driven by the Earth's rotation and by convection, and are set in motion by the movement of wands across the water surface
• Affect of current strength on coastal landscape

  Strength of the current has little effect of the coastal landscape system in terms of geomorphic processes, but the transfer of heat energy can be significant, as it directly affects air temp and therefore, sub-aerial processes
• Affect of rivers on coastal sediment budget

  Rivers are major sources of sediment input to the costal sediment budget - particularly coasts with steep gradient where rivers directly deposit material
• Where does sediment come from?

  Erosion of inland areas by water, wind, and ice as well as sub-aerial processes of weathering and mass movement
• Wave erosion and sediment budget

  Wave erosion is also the source of large amounts of sediment and makes a major contribution to sediment budgets

  - Cliff erosion can be increased by rising sea levels and is amplified by storm surge events (AO2: likely to get worse in the future
• Constructive waves and the movement of sediment

  Constructive waves bring sediment to the shore from offshore location and deposit it (marine deposition, adding to the sediment budget (tides and currents do the same)
• What can be done is a sediment budget is in deficit?

  Beach nourishment is one way n which a sediment equilibrium can be maintained

  - Used globally to preserve and protect coastal environment

  + Sustainable

  - Expensive
• What is freeze-thaw weathering?

  Water enters cracks/joints and expands by 9% when it freezes. In confined spaces this exerts a pressure on the rock, causing it to split or pieces to break off, even in very resistant rocks
• What is pressure release?

  When overlaying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface. this is significant in the exposure of sub-surface rocks such as granite
• What is thermal expansion?

  Rocks expand when heated and contract when cooled. If they are subject to frequent cycles of temperature change, then the outer layers may crack and flake off
• What is salt crystallisation?

  Solutions of salt can seep into the pore spaces in porous rocks. Here, salts precipitate, forming crystals. Growth of these crystals creates stress in the rock causing it to disintegrate.
• What is oxidation weathering?

  Some minerals in rocks react with oxygen, either in the air or in water. Iron is especially susceptible to this process. It becomes soluble under extremely acidic conditions and the original structure is destroyed. It often attracts the iron-rich cements that bind sand grind together in sandstone.
• What is carbonation weathering?

  Rainwater combines with dissolved carbon dioxide in the atmosphere to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which is soluble