coastal systems

What do you find in systems?

• processes

• inputs

• outputs

• equilibrium (over a long period of time)

• dynamic equilibrium

• energy

• sediment

• feedback (negative and positive)

Systems can also be open and closed

What types of energy act on a coastal system and how?

• kinetic

• thermal

• chemical

• gravitational potential

How do different energy types interact with the coastal system?

• The sun causes low pressure through thermal energy

• thus creates wind which adds kinetic energy

• this increases erosion and sediment stores

• leads to cliffs collapsing through gravitational potential energy

or

• heat energy makes chemical reactions faster

• higher rate of chemical weathering

or

• light energy causes higher rates of photosynthesis

• plant grows

• increased biological weathering

• cliff falls through gravitational potential energy

What is the difference between an open and closed system?

Energy and matter can leave in an open system

They can not in a closed system

List some inputs in a dynamic coastline?

• energy

• aeolian (wind)

• human inputs e.g. beach nourishment

• offshore

• coast cliffs depositing sediment

• fluvial (rivers) they contribute 95% of sediment

What are the main processes in a system?

Weathering (breakdown of rocks in place)

erosion (breakdown and removal of rock)

LSD

deposition (depositing of sediment)

What are the main outputs in a system?

• humans e.g. dredging

• offshore

• aeolian

• cliffs / headlands

• spits, bars, tombolos

• beaches

What is a sediment cell?

• It is a linked system of sources transfers and sinks of sediment along a section of coastline

• They are regarded as closed systems as its rare for sediment from other cells to be transferred because the cells are determined by their topography e.g. headlands and estuaries

• However this is not realistic and it is impossible for it to be a closed system

What is the point of sediment cells?

• to manage the coastline effectively and reduce the chances of unintended consequences up and down the coast from management.

• sediment cells are also split into sub cells too to help improve this process further

What is sediment budget?

the balance of sediment entering and exiting a section of the coast. It can be used to predict the changing shape of a coastline over time.

What is deficit and surplus?

deficit - outputs higher than inputs

surplus - inputs higher than outputs

Explain Flamborough head to sunk island

• there are source regions at the north part with a low energy environment - so more sediment. e.g. Smithic sands

• holderness coast - soft boulder clay and also the transfer zone through LSD

• sink / store region / output - sunk island, spurn head and the humber estuary marshes

What is the difference between a geomorphic process and a physical factor?

• geomorphic processes are the dynamic actions that shape the coastline. e.g. erosion, transport and mass movement

• Physical factors are environmental conditions or forces that drive these actions e.g. tide, current, geology

What are physical factors?

• They influence the way that processes work which affects the shaping of a landscape

• they vary in terms of their spatial (place to place) and temporal (over time) impacts

• in any one location, some factors will have more significance than others

What is fetch?

• distance over which the wind has blown

How does wind interact with and influence the coastal system?

• High wind speed and / or long fetch = more energy which means higher waves

• the wind imparts energy into the ocean surface by frictional drag - kinetic energy

Whats the difference between constructive and destructive waves?

Constructive:

• low flat wave spills over

• strong swash

• weak backwash

destructive:

• large steep wave plunges over

• weak swash

• strong backwash

How do waves interact and influence the coastal landscape system?

• high winds / long fetch

• causes high energy waves

• low levels of deposition and high levels of erosion meaning high levels of sediment

this can also apply for low winds and low fetch as it would be the opposite

What is a diurnal tide and a semi diurnal tide?

• diurnal - 1 tide every day

• semi diurnal - two tides every day (by far the most common)

What is tidal range?

The distance in meters between the high and low tide

How do tides interact with and influence the coastal landscape system?

• high tidal range means more erosion as waves can access higher up the cliff - more sediment input

• the tide brings in and takes out more sediment + energy

• semi -diurnal tides will change the small scale features on the beach twice a day whilst a diurnal tide only once a day.

How do currents impact and influence the coastal landscape system? Use an example

• weathering speed increases because the gulf stream current moves hotter water over to the UK from Caribbean - chemical reactions increase

• it can also bring in sediment through suspension

What is a small scale current?

A rip current

• a strong localized and narrow current of water that moves away from shore which cuts through waves and forms cusps and channels

• they take up little space and finish quickly

• they also take lots of sediment out of the system

What ares of geology influence coastal landscapes?

• structure (properties of individual rock types)

• lithology (the physical and chemical composition of rock)

What are the features of structure?

• bedding planes (boundaries that visibly separate individual layers of rocks)

• joints

• porosity (how much space there is in in a rock)

• permeability (how easy it is for water to flow in it)

• faults

highly structured cliff faces increase the surface area for more erosion / weathering

It also generally weakens the cliff structure

What are the impacts on variations in lithology?

Hard rock:

• basalt

• strong interlocking crystals

• very resistant to erosion and weathering

• e.g. cliffs and headlands

medium strength rocks:

• limestone / carbon rich rocks dissolve in weak acid

• lots of jointing and high structure

• arches can form

low strength rocks:

• red clay

• previously weathered material

• vulnerable to erosion

All of these contribute to system sediment amount

What is strata?

distinct parallel layers of rock or soil stacked one on top of each other

they influence the shape of the coastline

What is a horizontally bedded strata?

• undercutting wave action leads to rockfall and cliff retreat

• vertical cliff

What is a seaward dipping strata?

• undercutting by wave action removes basal support

• this causes the bedding planes to slide through mass movement

• forms a gradient

What is a landward dipping strata?

• loosened by weathering and wave action and are difficult to dislodge

• they gradually lower through weathering and mass movement

• forms a gradient