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 closedsystems
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
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 removematerial 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 hightidalrange
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
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
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 stormsurge 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 (marinedeposition, 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
What is solution weathering?
Any processes by which a mineral dissolves in water is known as solution
What is hydrolysis weathering?
This is a chemical reaction between rock minerals and water. Silicates combine with water, producing secondary minerals such as clays. Feldspar in granite reacts with hydrogen in water to produce china clay