Coastal landscapes and change Flashcards
(80 cards)
1
Q
What is the littoral zone?
A
- A zone running from the highest sea-level line to shallow offshore waters.
- It contains all the sediment and the waves and tides that move this around the zone.
- It is a zone of dynamic equilibrium, there are a wide range of natural processes which interact with this, as well as human activities interfering with them.
- Consists of the offshore, nearshore, foreshore and backshore.
2
Q
What are the characteristics of high energy coasts?
A
- Long fetch, destructive waves with strong backswash, and storms.
- High levels of erosion and transport.
- Cliffs, wave cut platforms, cracks, caves, arches, stacks and stumps.
3
Q
What are the characteristics of low energy coasts.
A
- Constructive waves, short fetches and calm conditions.
- Deposition ad transport.
- Barrier beaches, beaches, spits, tombolos, sand dunes, salt marches, bars, mudflats.
4
Q
What affects the shape of the coast?
A
- Geological factors
- Marine factors
5
Q
What is a concordant coast?
A
Arrangement of rock parallel to the coastline.
6
Q
What is a discordant coast?
A
Arrangement of rock perpendicular to the coastline.
7
Q
What is coastal morphology in relation to concordant and discordant coastlines?
A
- Concordant coastlines form coves like Lulworth.
- Discordant coastlines form headlands and bays
8
Q
What is wave refraction?
A
Once headlands and bays have formed, high energy waves concentrate at the headland as it sticks out, the energy dissipating before it reaches the bay.
9
Q
What are crevices, joints, and faults?
A
- Formed from the pressure or cooling of rock during rock formation.
- Crevice = narrow fissure in the rock.
- Joint = vertical bedding plane
- Fault = large fracture in the earth’s crust.
10
Q
What are bedding planes?
A
The spaces between each large horizontal layer of rock.
11
Q
What are caves, blowholes, and geos?
A
- Caves = Large gap in rock that doesn’t go all the way through.
- Blowholes = Sea cave eroding upwards and landwards.
- Geos = A long, narrow cleft in a coastal cliff.
12
Q
What are strata?
A
Large layers of rock (or soil).
13
Q
What do slopes in rock layers cause?
A
- Horizontal strata - stable and steady cliff.
- Vertical joints - weathering will cause cliff collapse.
- Steep seward layers - No weakness in sea facing cliff.
- Inland dip - Some weaknesses in bedding planes.
- Crisscross layers and joints - slide planes = much collapse.
14
Q
What is lithology?
A
Sedimentary/igneous/metamorphic rock types and cliff characteristics based on this.
15
Q
What are the recession rates for granite and limestone?
A
Granite - 1mm/yr
Limestone - 2.5cm/yr
16
Q
What are subaerial processes?
A
Weathering and mass movement.
17
Q
How does the permeability/porosity of rock affect erosion?
A
Water can enter porous rocks like sandstone, pool at the bottom on top of a non porous (e.g clay) layer, causing slipping and slumping.
18
Q
Why are some rocks vulnerable to chemical weathering?
A
They contain soluble minerals and are affected by hydrolysis or carbonation. E.g Limestone is water soluble, forming a carbonic acid. (This is an example of solution.)
19
Q
What is the role of coastal ecosystems/vegetation?
A
Stabilises soft sediment, low energy coastlines.
20
Q
What are salt marshes?
A
Fine muds, silts, clay particles deposited at the side of an estuary. This is colonised by algae and hardy pioneer plants (they must survive the salty conditions of high tides) before being succeeded my more vegetation and animals like lugworms as the plants trap sediment, building the marsh up above the level of the high tide so other plants are able to survive.
21
Q
What are sand dunes?
A
Strandline made of swash deposits traps sediment to form an embryo dune colonised by sea rocket. The dune becomes bigger and grows marram grass (yellow dunes). Then more plants grow (grey dunes) and finally trees and a dune slack as a dip is filled bc its below the water table (Mature dune). Can take 50-100 years for a dune sequence to develop, with the oldest dunes nearest the land and youngest nearest the sea.
22
Q
How are waves constructed?
A
Friction between the wind and the surface of the water. Fetch length and wind strength increases the power of the wave.
23
Q
What are dominant and prevailing winds?
A
Dominant - strongest wind direction.
Prevailing - most frequent wind direction.
24
Q
What are destructive waves?
A
Waves with a stronger backwash than swash, averaging 13-15 per minute in frequency.
25
What are constructive waves?
Waves with a stronger swash than backwash, averaging 6-8 per minute in wave frequency.
26
What are the 4 types of erosion?
- Hydraulic action
- Corrosion/saltation
- Abrasion
- Attrition
27
How is a wave cut notch formed?
Destructive waves erode away the base of the cliff forming a curved notch.
28
How is a wave cut platform formed?
As the wave cut notch becomes deeper, the above rock is unsupported, and will eventually collapse to form a flat or slightly sloping rocky area.
29
How are cliffs formed?
Vertical/near vertical slopes caused by waves undercutting the land.
30
How are stumps formed?
At the headland, refracted waves exert their pull force at weaknesses on the sides, first forming caves, then arches, stacks, and stumps.
31
What is longshore drift?
Waves approach the beach at a 30 degree website. The forward movement of the swash moves the sediment in the same direction as the dominant wind. The backwash then carries this sediment back down the beach at a right angle influenced by gravity, therefore carrying sediment down the beach in a zigzag pattern.
32
How are beaches formed?
Depositional feature, either sandy or pebbled. Sandy beaches have a gentle angle, pebbles are steeper.
33
How are offshore bars formed?
Long ridge of sand/pebbles formed in shallow water off a coast. Destructive waves break before reaching the beach They scour the seabed and throw material forwards in a heap.
34
How are barrier beaches formed?
Offshore bars move closer to the shore, forming a beach that protects the coastline behind it E.g Chesil beach.
35
How are spits formed?
Longshore drift carries material along a beach until it reaches an estuary, at which point material is deposited in the seabed, eventually forming a narrow strip of land across part of the estuary. This can also occur in bays.
36
How are tombolos formed?
Occurs when longshore drift carries sediment between an island and the mainland, forming a narrow ridge. E.g the Isle of Portland.
37
How are cuspate forelands formed?
Longshore drift occurs in two opposing directions to form two spits over a bay, that converge in the middle. Then, additional depositional processes fill out the slack water in the middle with sediment, eventually forming a low lying headland.
38
What is a sediment cell?
A section of coastline that essentially acts as a closed system with all the sources, transfers, and sinks that it needs (Although technically they can and do interact with each other). The UK coastline is divided into 11 of these cells.
39
What is weathering?
The breakdown of rocks at the earth's surface through exploiting their weaknesses:
- Freeze thaw
- Salt crystallisation
- Oxidisation
- Seaweed acids
- Boring molluscs
40
What is mass movement?
The movement downslope of rocks.
41
What are rock falls and talus slopes?
Occurs on steep slopes as cliffs are weathered, resulting in rock fragments falling to the base of the cliff.
42
What are block falls?
Occurs on steep slopes as cliffs are weathered, resulting in large block of rock being loosened, and sliding down the cliff face.
43
What is rotational slumping?
A section of cliff remains intact as it moves down the cliff along a curved slip plane. The vegetation layer on top of the cliff is usually still intact.
44
What is flow?
Unconsolidated sands or mudflow spills down the cliff face.
45
How do sea levels change?
Through isostatic, eustatic, and tectonic changes, as well as the influence of ice ages and climate change.
46
What is eustatic change?
Change in sea level based on the storage of water in glaciers and ice sheets.
47
What is isostatic change?
Change in land level based on whether ice sheets are on the land, causing the land to be compressed under the sheets, and the land around this to spring up. E.g in the UK scotland was compressed whilst the south was raised slightly. When the sheets melt, isostatic rebound occurs.
48
What is tectonic change?
Can affect the shape of the coast and therefore the coastal processes that occur on it.
49
What are emergent coastlines?
Coastlines that have risen after isostatic compression through isostatic rebound, e.g Raised beaches - a former beach raised out of the tide line through uplift; and Fossil cliffs - near vertical slopes initially formed by marine processes but now some distance inland.
50
What are submergent coastlines?
Coastlines sunk either as a result of sea level rise or isostatic sinking. E.g Rias - flooded river valleys; Fjords - flooded glaciated valleys.
51
What is thermal expansion?
When water heats up it expands.
52
What are the physical causes of coastal retreat?
Geology of the coast, marine and subaerial processes.
53
What are the human causes of coastal retreat?
Coastal defences, offshore dredging.
54
What factors affect rates of recession?
- Wind direction
- Tides
- Weather systems
55
How does wind affect recession rates?
Dominant winds produce the strongest waves, meaning some days one part of the coast will be worse affected than the next depending on the direction of the dominant wind.
56
How do tides affect recession rates?
At high tides, waves are more likely to reach the backshore and will therefore travel further.
57
How does weather affect recession rates?
High pressure - calm conditions. (Occurs in summer)
Low pressure - Fast recession rates. (Occurs in winter)
58
How do storm surges influence coastal recession?
They increase it.
59
How does climate change influence coastal recession?
Increases likelihood of storm surges as well as sea level rise, increasing recession rates.
60
What are the economic costs of recession for local communities?
Loss of buildings, jobs, income ect. The UK government does not provide compensation to people who have lost their homes to coastal erosion.
61
What are the social costs for local communities?
Loss of family members, temporary or permanent relocation, loss of livelihood and amenity areas.
62
What are environmental refugees?
Migration within or externally from a place severely affected by the impacts of climate change.
63
What are the pros and cons of hard engineering?
- Pros: Effective, can attract tourists.
- Cons: Expensive, eyesore, destructive to wildlife.
64
What are groynes
Wooden walls on a beach at right angles to the coast. Not too expensive but still £1000 per linear m. Assists tourism.
65
What are sea walls?
Large walls that prevent wave erosion at the coastline. Long lasting and efficient. Very expensive and unnatural.
66
What is rip-rap?
Boulders placed to break and dissipate high energy waves. Long lasting, can look unsightly and wont completely stop erosion at the cliff as some water will get through. Can also be used to hold back mass movement on a cliff.
67
What are revetments?
Sloped wooden walls a short distance before the backshore to weaken the strength of eroding waves. Cheaper alternative to sea walls but may need maintenance and can look bad.
68
What are offshore breakwaters?
Essentially rip rap in the sea as opposed to against a cliff.
69
What are gabions?
Pebbles in wire baskets that can make a wall to absorb some of the wave energy before it hits the cliff. Flexible placement and cheap, but aren't very strong, require maintenance and can be seen as ugly.
70
What are the pros and cons of soft engineering?
- Good for the environment, look natural.
- Expensive, may not be very effective
71
What is beach nourishment?
Replaces eroded sediment on a beach. Looks natural and attracts tourism but very expensive and not long lasting. also if sediment is dredged offshore it deepens the water which increases the destructive power of the waves.
72
What is cliff regrading?
Stable rock angle is calculated then artificially cut back. natural and effective so long as the base of the cliff is protected from erosion. However costs about £1 mill and natural conditions can overwhelm the defence.
73
What is cliff draining?
Water can be drained out of the cliff to prevent mass movement (slumping in particular). Looks natural and reduces mass movement, but difficult to implement and will not completely prevent mass movement, just reduce it.
74
What is dune stabilisation?
Monitoring and repairing dunes with geofabric, and replanting grasses, to keep them in place (they are natural barriers). Looks natural but may need to be fenced ff and powerful storms can reverse the management.
75
What is managed retreat?
Areas set aside for the sea to flood and erode. E.g farmland converted from saltmarsh can be allowed to flood again, or buer zones next to eroding cliffs so valuable property isn't lost. Allows natural processes to take place but needs agreement from property owners and is not compensated currently.
76
How is sustainable management used in the UK?
New focus on adaptation, moving away from hard engineering strategies to sustainable approaches. E.g new stages of SMPs, Thames estuary project ect.
77
What are holistic management strategies?
Acceptance of a complex interconnectivity of factors and recognition of the need for longer term plans and strategies.
78
What is an ICZM?
Integrated coastal zone management. Introduced in 1992 and adopted by the EU in 2002. Focuses on cooperation between all stakeholders.
79
What are SMPs?
Shoreline management policies. A national strategy for flood and coastal defence set out in 1993 based on the 11 zones. 4 strategies: hold the line, advance the line, managed realignment, no active intervention, based on CBA.
80
What is an EIA?
Environmental impact assessment that determines the positives and negatives of a development scheme before it is implemented. Rating scale from significant positive effects to significant negative effects.
