Coastal landscapes chapter ???

Question 1

what are coastal landscapes

Answer 1

• Coastal landscapes can be viewed as systems which is a set of interrelated objects comprising components and processes that are connected to form a working unit.
• Coastal landscapes systems store and transfer energy and material. The energy may be kinetic, potential or thermal.

Question 2

what does a coastal landscape have?

Answer 2

-energy and matter can be transported from neighbouring systems as an input and transferred to neighbouring systems as an output eg input of fluvial sediment

Inputs – including kinetic energy from wind, waves, thermal energy, material from. Marine deposition
Outputs- including marine and wind erosion from beaches and rock surfaces; evaporation.
Throughputs - which consists of stores including beaches and nearshore sediment accumulations and flows such as longshore rift along a beach

Question 3

System feedback in coastal landscape

Answer 3

• when a systems inputs and outputs are equal this results in equilibrium. In a coastal landscape this is the rate at which sediment is added to the beach equals the rate its removed.
• when equilibrium is disturbed it undergoes self-regulation and changes its form in order to restore the equilibrium. This is known as dynamic equilibrium and an example of negative feedback.

Question 4

Sediment cells

Answer 4

• Sediment cells are areas along the coastline and in the nearshore area where the movement of material is largely self-contained.
• a sediment cell is also regarded as a closed system (no sediment cells transferred from one cell to another.

Question 5

what is the development of coastal landscapes influenced by

Answer 5

• climate/weather patterns/seasons
• wave type and strength
• wind direction
• fetch length and direction
• currents

Question 6

Wind

aeolian

Answer 6

• Wave action is the source of energy for coastal erosion and sediment transport.
• Generated by frictional drag of winds moving across the ocean surface.
• Higher wind = longer fetch / larger the wind = more wind energy
• Wind is a moving force and as such is able to carry out erosion, transportation and deposition itself. These aeolian processed contribute to coastal landscapes.

Question 7

Waves

Answer 7

• A wave possesses 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.
• moving waves do not move water forward but in a circular motion to the individual water molecules

Question 8

The amount of energy in a wave in deep water equation

Answer 8

P = H2T
Power (kw) =Wave height(m)2 x Wave period(S)

Wave period = Time between wave crests in seconds

Question 9

Wave Anatomy

Answer 9

• The highest surface of a wave is the Crest and the lowest is the trough:
• Wave height is the vertical distance between the crest and trough
• The horizontal distance is the wavelength

*look at picture in your notes or pg 4 of textbook

Question 10

swell waves and storm waves

Answer 10

• Swell waves: Waves formed in open oceans travel huge distances and have a long wavelength and a wave period of 20 seconds.
• Storm waves: waves generated more locally and have a short wavelength and shorter wave period.

Question 11

what happens when a wave goes to shallow water

Answer 11

• At depth the deepest water molecules come into contact with the sea floor causing friction between the sea floor and the water then:

1. wavelength decreases and successive waves start to bunch up.
2. The deepest part of the wave slows down more than the top of the wave.
3. Wave begins to steepen as the crest advances ahead of the base
4. water depth is then less then 1.3 x wave height
5. The wave then topples over and breaks against the seashore.

Question 12

Types of breaking waves

Answer 12

Spilling – steep waves breaking onto gently sloping beaches; water spills gently forward as the wave breaks
Plunging- moderately steep waves breaking onto steep beaches; water plunges vertically downwards as the crest curls over
Surging- low-angle waves breaking onto steep beaches; the wave slides forward and may not actually break.

Question 13

what happens after a wave breaks

Answer 13

• After a wave breaks water moves up the beach as swash, driven by energy from the breaking of the wave
• The speed of the water decreases the further it travels due to friction
• When there is no more energy to move forward the water is drawn back and this is the backwash

Question 14

constructive and deconstructive waves

Answer 14

Constructive waves

• low height
• long wavelength
• low frequency (6-8 per minute)
• Break as spilling waves
• strong swash due to long wavelength and weak backwash

Deconstructive wavelength

• A greater height
• Shorter wavelength
• Higher frequency (12 -14 per minute)
• Break as plunging waves
• weak swash due to friction from the steep beach and strong backwash

Question 15

Tides

Answer 15

• Tides are periodic rise and fall of the sea surface and are produced by the gravitational pull of the moon and the sun.
• The moon pulls water towards it creating high tide and there is a compensatory bulge on the opposite side of the earth.
• Between two bulges there is a low tide
• The highest tide will occur when the moon, sun and earth are all aligned (happens twice a year each lunar month)

Question 16

tidal range

Answer 16

Tidal range- a significant factor in development of coastal landscapes.

^So tidal energy 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.

Question 17

Geology

• Two aspects of geology are lithology and structure

Answer 17

Lithology – describes the physical and chemical composition of rocks.
- some rock types such as clay have a weak lithology with little resistance to erosion, weathering and mass movements because bonds between particles make up the rock are weak

Structure – concerns the properties of individual rock types such as jointing, bedding and faulting also including the permeability of rocks

• In porous rocks, such as chalk, tiny air spaces separate the mineral particles. These pores can absorb and store water – known as primary permeability
• Water seeps into limestone because of it many joints and this is known as secondary permeability. The joints are easily enlarged by solution.

Question 18

Concordant coasts

Answer 18

Concordant coasts – where rocks lie at right angles to the coast they create a discordant platform: more resistant rocks form headlands; the weaker rocks form bays

• structure also includes the angle of dip of rocks and can influence on cliff profiles.

Question 19

Currents

Answer 19

• Nearshore and off-shore currents influence coastal landscape systems.
• Rip currents are important in the transport of coastal sediment caused by tidal motion or by waves breaking at right angles to the shore
• A cellular circulation is generated by differing wave heights parallel to the shore
• water from the top of the waves travels further up the shore and returns to the where the lower bit of the wave broke

Question 20

• Ocean currents

Answer 20

are much larger scale phenomena, generated by the earth’s rotation and by convection set in motion by the movements of the winds across the water surface.
-warm ocean currents transfer heat energy from low latitudes towards the poles.

Question 21

The 1953 North Sea storm surge

Answer 21

• a combination of high spring tide and a severe European windstorm over the north-sea caused a storm tide.
• The storm surge struck the Netherlands, north-west Belgium, England and Scotland.
• The combination of wind, high tide and low pressure led to water level of more than 5.6 metres above mean sea level locations.
• The floods hit on the night of 31st January / 1st February 1953.
• 307 people dies in southeast England, 58 in Canvey island alone. An estimated 160,000 hectares of land was flooded and over 24,000 homes destroyed

Question 22

The Thames barrier programme

Answer 22

• The Thames barrier is a movable barrier system that when needed, it is closed (raised) during high tide; at low tide, it can be opened to restore the river’s flow towards the sea.

Question 23

Rance Tidal power station in France

Answer 23

• When the tide is coming in, the water on the sea-side of the barrage is higher than the estuary side; therefore water will flow from the sea side through the turbine into the estuary. When the tide is going out, the exact opposite occurs. As such, the turbines that were installed in the Rance Power Station have the capability to produce power in either direction.

Question 24

Swansea Bay Tidal Lagoon

Answer 24

The world’s first tidal lagoon power plant. A tidal lagoon is a ‘U’ shaped breakwater, built out from the coast which has a bank of hydro turbines in it. Water fills up and empties the man-made lagoon as the tides rise and fall. They will generate electricity on both the incoming and outgoing tides, four times a day, every day.

Question 25

- Shore platforms

Answer 25

(erosional) - At high tide the sea attacks a weakness in the base of the cliff. A wave-cut notch is created by erosional processes such as hydraulic action and abrasion. As the notch becomes larger the cliff becomes undercut and collapses as the result of gravity. The cliff retreats due to being unsupported. Then at low tide, the material from the collapsed cliff face is eroded and transported away, leaving a shore platform

Question 26

- Estuary (depositional)

Answer 26

– Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea, created thorough deposition, as the river will lose energy and so drop the sediment its holding and then at low tide the silt that has flocculated is left leaving mud flats and sand banks.

Question 27

Terrestrial - sediment

Answer 27

- Rivers are major sources of sediment input to the coastal sediment budget and this is also true for coasts with a steep gradient where rivers directly deposit sediment at the coast. - Sediment delivery to the shoreline can be irregular mostly during floods - The origin of the sediment is the erosion of inland areas by water, wind and ice as well as sub aerial processes of weathering and mass movement - Wave erosion is also the source of sediment - Cliff erosion can be increased by rising sea levels and is amplified by storm surge events - Longshore drift can also supply sediment from 1 coastal area by moving it along the coast to adjacent areas

Question 28

Offshore sediment

Answer 28

- Constructive waves bring sediment to the shore from offshore locations and deposit it adding to the sediment budget (Tides and currents do the same) - Winds blow sediment from other locations including exposed sand bars, dunes and beaches elsewhere along the coast - This aeolian material is generally fine sand as wind has less energy than water so cannot transport very large particles

Question 29

Human sediment

Answer 29

- When the coastal sediment budget is in deficit, beach nourishment is the one way in which a sediment equilibrium can be maintained - This type of management has been adopted all over the world in order to preserve and protect the coastal environment - Sediment can be brought in by lorry and dumped on the beach before being spread out by bulldozers - Alternatively, sand and water can be pumped onshore by pipeline from offshore sources - Low bunds hold the mixture in place while the water drains away leaving sediment behind - Wind, waves and longshore drift movements can also remove sediment by subtracting the amount of sediment lost from the amount of sediment gained determined if the sediment budget is in surplus or deficit or equilibrium.

Question 30

Physical or mechanical weathering:

Answer 30

Freeze thawing – Water enters cracks/joints and expands when it freezes causing it to split or pieces of rock to break off Pressure release – When overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures. Significant in sub-surface rocks like granite. Thermal expansion – Rocks expand when heated and contract when cooled. If they are subject to frequent temperature change then the outer layers may crack and flake off. Salt crystallisation – Solutions of salt can seep into the pore spaces in porous rocks. Here the salts precipitate forming crystals

Question 31

Chemical weathering

Answer 31

- Causes the decay of rock involving chemical reactions between moisture and minerals within the rock - Carbonation can be more effective in low temperatures as carbon dioxide is more soluble in cold water than in warm water

Question 32

chemical weathering processes

Answer 32

Oxidation – Some minerals in rocks react with oxygen, either in the air or in water. Iron is especially susceptible to this process Carbonation – Rainwater combines with dissolved co2 to produce weak carbonic acid which then reacts with calcium carbonate in rocks like limestone Solution – Some salts are soluble in water. Any process by which minerals dissolve in water is known as solution Hydrolysis – A chemical reaction between rock minerals and water Hydration – water molecules added to rock minerals create new minerals of a larger volume causing the surface flaking in many rocks partly because some minerals expand during the chemical change because they absorb water

Question 33

Biological

Answer 33

- May consist of physical actions such as growth of plant roots and chemical processes Tree roots – Grow into cracks or joints in rocks and exert outward pressure. When trees topple their roots can also exert leverage on rock and soil bringing them to the surface exposing them to weathering. Burrowing animals have the same effect Organic acids – Produced during decomposition of plant and animal litter cause soil water to become more acidic and react with some minerals in a process called chelation

Question 34

Mass movement

Answer 34

Rockfall – rocks become detached from the slope by physical weathering processes which then fall to the foot of the cliff under gravity Slides – These may be linear, with movement along a straight line slip plane, such as a fault or a bedding plane - Rotational slides are also known as slumps and are common in weak rocks

Question 35

Erosion

Answer 35

Abrasion – waves armed with the rock particles scour the coastline; rock rubbing against rock Attrition – occurs when rock particles are transported by the wave and collide with each other and become smoother and more well rounded and smaller Hydraulic action – occurs when waves break against a cliff face and air and water get trapped in the cracks and crevices becoming compressed. As the wave recedes the pressure is released and the air and water expands and the crack is widened Pounding – occurs when the mass of a breaking wave exerts pressure on the rock causing it to weaken. Solution – dissolving of minerals like magnesium carbonate minerals in coastal rock

Question 36

transportation

Answer 36

Traction - large, heavy pebbles are rolled along the river-bed. This is most common near the source of a river, as here the load is larger. Saltation - pebbles are bounced along the river-bed, most commonly near the source. Suspension - lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river. Solution - the transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.

Question 37

coastal sediment budget

Answer 37

refers to the balance between sediment added to and removed from the coastal system; in this respect the coastal sediment budget is like a bank account. When more material is added than is removed, there is a surplus of sediment and the shore builds seaward.

Question 38

Deposition

Answer 38

Material is deposited when there is a loss of energy caused by a decrease in velocity and/or volume of water Tends to take place in coastal landscape systems: - Where the rate of sediment accumulation exceeds the rate of removal - When waves slow down immediately after breaking -at the top of the swash where for a brief moment the water is no longer moving - during the backwash, when water percolates into the beach material - In low energy environments such as sheltered from winds and waves eg estuaries

Question 39

Deposition effects

Answer 39

- The velocity at which sediment particles are deposited is known as settling velocity - The larger and heavier particles require more energy to transport them - As flow velocity decreases the largest particles being carried are deposited first and so on until the finest particles are deposited

Question 40

Fluvial processes

Answer 40

occurs in rivers

Question 41

fluvial erosion

Answer 41

- The rivers mains source of a river’s sediment load is fluvial processes in the upper catchment - Rivers use similar processes with most channel erosion occurring during high-flow, high energy events - Sediment is also derived from weathering and mass movement processes that result in material moving into river channels from valley sides

Question 42

fluvial transportation

Answer 42

Transportation – same as waves, Traction suspension, saltation and solution

Question 43

Fluvial deposition

Answer 43

– As rivers enter the sea there is a noticeable reduction in their velocity as flowing water moves from the channel into a static body of sea water - Indeed, tides and currents may be moving in the opposite direction to the river flow, providing resistance to its forward movement - Available energy is reduced and so some, or all, of the river’s sediment load is deposited - As the reduction in energy is progressive, deposition is sequential, the largest particles are deposited first and the finest are carried further out to sea - The meeting of the fresh water and salt water causes flocculation of clay particles which as a result they become heavier and sink to the sea bed

Question 44

Aeolian processes

Answer 44

exposure to open sea surfaces, influenced by winds and blowing onshore

Question 45

aeolian Transportation

Answer 45

- With the exception of solution, moving air is able to transport material using the same mechanisms as water moving in rivers and waves. - Only the smallest grains can be carried in suspension

Question 46

Aeolian deposition

Answer 46

- Materials carried by the wind will be deposited when the wind speed falls, usually as a result of surface friction - In coastal areas this will occur inland, where friction from vegetation and surface irregularities is much greater than on the open sea.