Coastal Landscape & Change Flashcards
(83 cards)
1
Q
Characteristics of high energy coasts
A
Destructive Waves, Long fetches, high Rates of erosion, caves, arches, stacks and stumps,cliffs and wave cut platforms
2
Q
Characteristics of a low energy cost
A
Constructive waves, shorter fetch, higher rates of deposition, spits and bars, beaches, sand dunes and salt marshes
3
Q
What is the littoral zone?
A
A series of sub-zones to represent the features of the wider coastline from sea to land
4
Q
What are 4 sub-zones in the littoral zone?
A
Backshore
Nearshore
Offshore
Foreshore
5
Q
The littoral zone in/outputs:
A
Sediment is the key inout and output of the system
Inputs - waves, currents and wind
Outputs - washed out into the sea by deposition
6
Q
What are concordant coastlines?
A
Alternating bands of hard snd soft rock parrallel to the coast
7
Q
What are discordant coastlines?
A
Alternating bands of hard and soft rock at 90* to the coast
8
Q
What type of coastline are erosional landforms more common? (concordant vs discordant)
A
More common on discordant coastlines because erosion happens ay different rates along their length
9
Q
What is longshore drift?
A
The movement of material along the coast
10
Q
What are strata?
A
layers of rock
11
Q
What are bedding planes? (Horizontal cracks)
A
A line in rocks separating two different layers: one usually more resistant to erosion, one usually weaker
12
Q
What are joints? (Vertical cracks)
A
These are fractures, caused either by contraction as sediments dry out or by earth movements during uplift
13
Q
What are folds?
A
Formed by pressure during tectonic activity which makes rocks buckle and crumple (Lulworth Crumple)
14
Q
What are faults?
A
Formed when the stress or pressure to which a rock is subjected exceeds its internal strength (fracture) . The faults then slip or move along fault planes.
15
Q
What is dip?
A
Refers to the angle at which rock strata lie (horizontally, vertically, towards sea or inland)
16
Q
Haff Coastline
A
Consist of concordant features
Long spits of sand and lagoons
Aligned parallel
17
Q
What type of plant lives in low nutrients and high salt concentration?
A
Pioneer Plants e.g Lyme grass
18
Q
Describe the order of the beach (biomes)
A
Embryo Dunes Building dunes Various herbs Scrub Forrest
19
Q
Wavelength
A
The distance between the crests of two waves
20
Q
Wave crest
A
Highest point on the wave
21
Q
Wave trough
A
Lowest point on the wave
22
Q
Destructive Waves
A
Stronger backwash than swash
Remove sediment from a beach or cliff
Frequency: 13-15 per minute
23
Q
Constructive Waves
A
Swash is more powerful than backwash
Sediment is moved up the beach
Frequency: 6-8 per minute
24
Q
Negative Feedback
A
Helps to maintain a balance within the system e.g rock falls -> protects base of cliff
25
Positive feedback
Tends to change the balance until a new equilibrium is reached e.g damage to sand dunes
26
The amount of sediment available within a cell is called the…
Sediment budget
27
Sediment Cell concept:
Erosion, transport and deposition work in a linked system. A sediment cell has sources, transfers and sinks. Each cell can be regarded as a closed system when there are huge Barriers between them.
28
What are environmental refugees?
People forced to migrate as a result of changes to the environment
29
Kiribati
Consists of 33 widely spread islands, which stretch across and area of the Pacific Ocean nearly as wide as the USA.
Low lying islands + sea level rise means people are being forced to migrate to places like New Zealand. Sea level rising by 1.2cm a year. (Four times faster than global average)
30
What is traction? ( marine transport)
Relatively large and heavy rocks are rolled along the seabed
31
What is saltation? ( marine transport )
Smaller and lighter rocks ‘bounce’ along the seabed
32
What is solution? ( marine transport)
Dissolved materials are carried by the sea
33
What is suspension? ( marine transport)
Fine materials such as clay and sediment is carried by the sea
34
What are the four types of marine transport?
Suspension
Traction
Solution
Saltation
35
What is tidal range?
The relative difference in height between high and low tide
36
What are the four types of erosion?
Hydraulic action
Abrasion
Corrasion
Attrition
37
What is hydraulic action?
Waves breaking at the foot of a cliff force air in cracks to be compressed. Loose rocks are dislodged and removed. When the wave retreats the compressed air rushes out of the crack and can further weaken faults in the cliff face.
38
What is abrasion?
Abrasion is the sandpaper effect of loose rocks being scraped along bare rock. It often smooths and polishes the rock.
39
What is corrasion?
Corrasion is when rock caught up in surging waves are hurled at a cliff face – causing it to be chipped and gauged.
40
What is attrition?
Attrition is when rocks carried by seawater collide – gradually making them smaller and smoother.
41
What are the types of weathering?
```
Freeze-Thaw Weathering (Mechanical)
Wetting and Drying ( Mechanical )
Salt Weathering ( Mechanical )
Carbonation ( chemical)
Plant Roots ( biological )
Animals ( biological )
```
42
Explain freeze-thaw Weathering and it’s effects
Water enters a crack or joint in the rock when it rains, then freezes. This then expands in volume and breaks apart and forces the cracks wider.
43
Explain Wetting and drying
Frequent cycles of wetting and drying are common on the coast, rocks rich in clay expand when they get wet and contract when dry.
Causes rocks to crack up and break up.
44
Explain salt Weathering
When salt water evaporates it leaves salt crystals behind. These can grow over time and exert stress on the rock.
Causes the rocks to break up.
45
Explain carbonation
Rainwater absorbs carbon dioxide from the air to form a weak carbonic acid. This reacts and dissolves the rock e.g limestone.
Dissolves the cliff face
46
Explain plant roots
Plant roots start to grow into small cracks in a cliff face. Weaken as the roots grow thick.
Breaks up the rock.
47
Explain Animal Weathering
Birds and animals dig burrows into the cliff. Marine organisms are also capable of burrowing into rocks.
Weakens the rock face.
48
How is a storm surge formed?
When air pressure is low over the sea, the water is able to rise upwards,forming a dome of seawater under the depression. The lower the air pressure, the higher the dome will be.
49
Bangladesh - Storm surge case study
Country most at risk from sea level rise. 40% of all recorded storm surges have occurred in Bangladesh. In 1970 a storm surge killed 500,000 people and storm surges have killed 1.3 million peopl since.
50
How are coastal management decisions made?
Cost-benefit analysis - considers the social and economic aspects. The benefits of a scheme are divided by the costs of building and main taining it.
Environmental impact assessments - try to assess the effects any strategy will have upon an area. Important on coastlines of attractive scenery and ecosystems are valuable tourist assets.
Feasibility studies - is the engineering planned suited to the local geology or coastal processes?
Risk assessment - involves taking decisions in the light of possible risks, important to insurance and legal claims.
Shoreline management plans - try to do decide upon the most appropriate scheme for each part of the littoral cell, in discussion with all parties.
51
Factors effecting rates of recession:
Wind direction - changes daily, dominant winds makes larger waves
Tides - high vs low tide
Weather systems - hot and cold air results in changes in conditions. High pressure = calm conditions // low pressure = strong winds
52
Hold the existing shoreline :
Intervention with maintenance of existing defences and building of new defences e.g sea walls, revetments, groynes
53
Advance the existing shoreline :
Intervention with building of new defences on the seaward side e.g artificial reefs and deposited sediment
54
Managed realignment of the shoreline :
No planned intervention, with natural processes operating without interference, but monitoring and managing the processes in certain places
55
No active intervention :
do nothing, with no investment in defences or maintenance of any existing defences these coastlines will normally retreat
56
Eustatic Sea level change
When the sea level rises or falls. Global scale.
| E.g climate change, melting ice caps means higher sea level.
57
Isostatic Sea level change
When the land rises or falls, occurs locally.
E.g during glacial periods the increase height of the ice sheets make the land sink, when these melt isostatic rebound occurs. This is when it rises back to normal.
E.g England - North vs South
58
Tectonic Sea level change
Movement of tectonic plates that affects sea level. Uplift of mountain ranges and coastal land at destructive and collision plate margins. Rising plates under the sea displaces large amounts of water.
E.g 2004 Boxing Day tsunami - displaced 30dm3
59
Raised beaches
As the land rose as a result of isostatic rebound former shoreline platforms and their beaches were raised above the present sea level.
E.g West coast of Scotland
60
Fossil Cliffs
The remains of eroded cliff lines. Can be found behind the raised beach, with wave-cut notches and caves.
E.g isle of Arron
61
A Ria (submergent landforms)
This is a river valley that’s been flooded by the eustatic rise in sea level. They’re almost exactly like a typical river valley but they have even more water in them.
E.g South-West England
62
Dalmation Coastlines (submergent landform)
Formed as a result of a rise in sea level
Valleys and Ridges run parallel to each other
When sea level rose the tops of the ridges were left as a series of offshore islands.
E.g Croatia
63
A fjord (submergent landform)
A fjord is formed when a glacier retreats, after carving its typical U-shaped valley, and the sea fills the resulting valley floor. This forms a narrow, steep sided inlet (sometimes deeper than 1300 metres) connected to the sea. E.g Norway, New Zealand and Chile
64
A Fjard (submergent landform)
Flooded inlet. Fjards are a glacial depression or valley that has much lower relief than a fjord.
65
What are the four types of submergent landforms/coastlines?
A Ria
A Fjord
A Fjard
Dalmation Coast
66
Holderness Coast - Location and background
The holderness coast is one of the Europe’s fastest eroding coastline. 2 m per year. The Holderness Coast is located on the east coast of England. It extends 61 km from Flamborough in the north to spurn in the south.
67
Fetch
How far the waves have traveled.
| Holderness has a long NE Wind, as a result they have large powerful waves.
68
Physical factors effecting coastal erosion:
```
Geology
Weakly consolidated rocks
Subaireal processes
Large destructive waves
Large scale mass movement
Constant Weathering
Small constructive waves
Resistant rock
Marine processes
```
69
Human factors effecting coastal erosion:
Coastal Defences
| Offshore dredging
70
How are spits formed?
Formed when prevailing wind blows at an angle to the coastline, resulting in longshore drift
E.g spurn head
70
How are swash and drift aligned beaches formed?
Drift aligned beaches are made when waves break at an angle.
Swash = Angle
Backwash = Perpendicular
Beaches that face the waves are swash beaches
72
What is an offshore bar?
Long ridge of sand and pebbles found a short distance out to sea. It forms in shallow water, where destructive waves break before reaching the beach.
73
How are barrier beaches formed?
Exposed sandbars that may have formed during the period of high water level of a storm or during the high tide season
74
How are tombolos formed?
This is when a small island connects with a spit due to shallow waves surrounding the island
75
How are Cuspate forelands formed?
When LSD is going in two opposite directions it forces sediment out into a triangular shape.
76
Adaption
Refers to policies which are designed to reduce existing impact.
77
Mitigation
Policies which are designed to delay, reduce or prevent.
78
Groynes (hard engineering) + advantages and disadvantages
Right angles to the coast, slow down LSD. They make beaches wider and higher so waves expend there energy on it rather than back shore.
Advantages - maintain the size of the beach, enhance the beach for recreational amenity assisting tourism, less expensive than sea walls
Disadvantages - expensive, not natural and people may find it ugly, terminal groyne syndrome
79
Sea Walls (hard engineering) + advantages and disadvantages
Parallel to the backshore. Recurved sea walls use the shape of a wave to direct the water into a following wave, reducing wave energy.
Advantages - long lasting concrete, give people confidence and security, tops can be used for promenades, prevent high water levels from moving inland
Disadvantages - most expensive type of coastal defences (£5000 per linear metre), may be considered ugly, reduce supply of sediments which may affect other coastal areas nearby
80
Rip-rap (hard engineering) + advantages and disadvantages
Boulders, usually granite, resistant to erosion,large surface area to break up waves
Advantages - long lasting and flexible use, can be placed on susceptible points on the backshore to protect the base of a sea wall or to be used as a breakwater or groyne
Disadvantages - maybe look unsightly and even natural rocks maybe contrast with the local geology, access difficulties as they are dangerous to climb over, seawater can still move through it
81
Beach nourishment (soft engineering) + advantages and disadvantages
Replaces beach sediment that may have been eroded or transported by LSD
Advantages - uses natural sediments so the beach looks natural, supports tourism industry
Disadvantages - does not last long, especially under winter storm conditions so may have to be repeated frequently, sediment may have been dredged from offshore so changing the sediment cell, waves approach with more destructive energy because its deeper
82
Cliff regrading (soft engineering) + advantages and disadvantages
The lithology of a cliff may be unstable and prone to sudden collapses, so to remove this engineers calculate a stable slope angle based on rock characteristics. Artificially cut back to a stable angle.
Advantages - natural looking slope, should remain stable if the base of th slope is protected from marine erosion
Disadvantages - Some land and property will be lost when the slope angle is changed, costs about £1m, extreme natural conditions may overwhelm the changes
83
Dune stabilisation (soft engineering) + advantages and disadvantages
Monitoring dune condition and repairing them with geofabric or replanting grasses together with in filling of slacks will help keep them in place.
Advantages - looks natural and is an effective barrier to higher sea levels and tides, provides natural ecosystems
Disadvantages - maybe need to be fenced off during works, which reduces amenity value in the short term, powerful storms may ensure that this approach only works for a short while
