How can coastal landscapes be viewed as systems?

The components of open systems

Open System: Energy and matter can be transferrred from neighbouring systems as an input and also as an output.
Inputs: kinetic energy from the wind and and waves, thermal energy from the sun and potential energy from the position of material on slopes.
Outputs: marine and wind erosion from beaches and rock surfaces - evaporation.
Throughputs: consist of stores including beach and nearshore sediment accumulations, and transfers such as the movement of sediment along a beach by longshore drift.

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When a systems inptuts and outputs are equal, a state of equillibrium is reached.
In a coastal landscape, this could happen when the rate at which sediment is being added to the beach equals the rate at which sediment it removed from the beach - therefore the beach will remain the same size.
When the equillibrium is distubred, the system undergoes self-regulation and changes its form in order to restore the equillibrium.
This is known as dynamic equillibrium - its an example of negative feedback.

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Winds: The higher the wind speed and the longer the fetch, the larger the waves and the more energy they have. Wind is a moving force and is able to carry out erosion, transportation and deposition. These aeolian processes contribute the the shaping of many coastal landscapes.
Waves: A wave has potential energy as a result of its position above the wave trough, and kinetic energy caused by the motion of the water within the wave. Constructive waves form berms and destructive waves form beach cliffs.
Tides: The moon uses gravitational pull to pull water towards it, creating a high tide, and there is a compensatory bulge on the other side of the earth. At locations between two bulges there will be low tide. The highest tide will occur when the moon, sun and earth are all aligned - so the pull is at its strongest. Tidal range can be a significant factor - it influences where wave action occurs, the weathering processes on land exposed between tides, and the potential scouring effect of waves along coasts with a high tidal range.

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Geology: Lithology (physical and chemical composition of rocks) - Some rock types, such as clay, have weak lithology, with little resistance to erosion, weathering and mass movements. This is because the rock's bonds are quite weak. These types of rocks are more likely to form bays. Others, such as basalt, made of dense interlocking crystals, are highly resistant and are more likely to form cliffs and headlands. Others, such as chalk and carboniferous limestone are soluble in weak acids and thus vulnerable to the chemical weathering process of carbonation. Structure - in porous rocks, such as chalk, pores seperate the mineral particles. These pores can absorb and store water = primary permeabilty. Carboniferous limestone is also permeable, but water seeps into it because of its many joints = secondary permeability.

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Currents: Rip currents play and important role in the transport of coastal sediment. They are caused either by tidal motion or by waves breaking at right angles to the shore. Once they form, they modify the shore profile by creating cusps which help perpetuate the rip current, chanelling flow through a narrow neck. Ocean currents are much larger scale phenomena, generated by the earths rotation and by convection, and are set in motion by the movement of winds across the water surface. Warm ocean currents transfer heat energy from low latitudes towards the poles. They particulary affect western-facing coastal areas where they are driven by onshore winds. Cold ocean currents do the opposite, moving cold water from polar regions towards the equator, and are driven by offshore winds.

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Terrestrial: Rivers are major sources of sediment input to the coastal sediment budget and this is particulary true of coasts with a steep gradient, where rivers directly deposit their sediments at the coast. Sediment delivery to the shoreline can be intermittant, mostly occuring during floods. Wave erosion is also a source of large amounts of sediment and makes a major contribution to coastal sediment budgets. Longshore drift can also supply sediment from one coastal area to another.
Offshore: Constructive waves bring sediment to the shore from offshore locations and deposit it, adding to the sediment budget. Tides and currents and winds do the same.
Human: Beach nourishment is one way in which a sediment equillibrium can be maintained.

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