Coasts Flashcards
1
Q
What are the subdivided areas of the littoral zone?
A
- offshore - beyond the influence of breaking waves
- nearshore - intertidal and within the breaker zone; used for fishing, trade and leisure
- backshore - above high tide and the influence of normal wave patterns; may have a storm beach further up
2
Q
Rocky coasts key points
A
- subject to erosion
- tend to be steep or vertical in profile
- attacked by weathering and mass movement processes
- often a high energy environment
3
Q
Plain coasts key points
A
- deposited landscapes of sand, shingle and mud
- low, flat landscapes, often poorly drained
- often a low energy environment
- dominated by processes of accretion so the coastline advances seaward
4
Q
What are the three elements to geological structure?
A
- Different layers of rock exposed in a cliff - strata
- Degree of tilting and folding by tectonic activity - deformation
- Fracturing that may have moved rocks from their original positions - faulting
5
Q
What are the two types of coast the geological structure produces?
A
- Concordant - when rock strata run parallel to the coastline
- Discordant - when different rock strata intersect the coast at an angle so rock type varies along the coastline
6
Q
Concordant coast example
A
- The Dalmation Coast in the Adriatic sea:
- limestone been folded by tectonic activity into a series of anticlines and synclines that trend parallel to the sea
- the syncline basins have been drowned by sea level rise
- the anticlines have produced long narrow offshore islands
7
Q
Discordant coasts key points
A
- Dominated by headlands and bays
- Less resistant rocks are eroded to form bays
- More resistant rocks remain as headlands protruding into the sea
- Headlands and bays change over time because headlands are more eroded than bays - due to refraction
8
Q
What is wave refraction?
A
- in deep water wave crests are parallel
- as water becomes shallower waves slow down and increase in height
- in bays - wave crests curve to reflect their shape and wave height increases
- wave action is concentrated on headlands
9
Q
What are cliff profiles affected by?
A
- resistance of rock to erosion
- dip of rock strata
10
Q
Other geological features influencing cliff profiles and can intiate notches and caves
A
- faulting can expose rocks to erosion as they are areas of weakness
- natural cracks in rocks (jointing) can also be areas of weakness
11
Q
Key points of stability
A
- vegetation roots bind sediments together making them more resistant to erosion
- when submerged plants protect the surface from erosion
- plants also protect sediment from wind erosion by reducing wind speed through fraction
- plants that grow as a succession in coastal environments are specially adapted xerophytes or halophytes
12
Q
Key points about sand dunes
A
- sand is deposited by the sea in low energy conditions
- wind may then move the sand to make dunes further up the beach
- these in turn become colonised by stabilising plants
13
Q
Key points about salt marshes
A
- sheltered river estuaries or zones in the lee of spits are areas where there are extensive accumulations of silt and mud aided by flocculation and gentle tides
- these intertidal areas are colonised by vegetation and over time this may develop into a salt marsh
14
Q
What is wave energy controlled by?
A
- the force, direction and duration of wind
- the fetch - the longer the fetch the more energy a wave has
15
Q
How do beaches change over time due to the types of waves?
A
- daily - as a storm passes destructive waves become constructive and berms are created
- seasonally - storm beaches created mostly in winter
- long term - more storms may occur due to climate change with higher storm beaches
16
Q
What is the rate of coastal erosion affected by?
A
- lithology - harder rock is more difficult to erode - some resistant rock can be eroded along joints or cracks
- structure and dip; steep cliffs form if rocks dip inland whereas rocks that dip seaward produce gentler slopes
- wave steepness; steeper, high energy waves have more power to erode
- wave breaking point; waves breaking at the foot of a cliff have more energy to erode
- width of beach - wider beaches absorb some of the waves energy and protect the coastline
- nature of the beach; pebbles dissipate energy from waves through friction and percolation
17
Q
Cliffs, headlands and bays key points
A
- form when rocks of differing hardness are exposed together at a coastline
- tougher, more resistant rocks tend to form headlands with cliffs
- weaker rocks are eroded to form sandy bays
18
Q
Wave cut platforms key points
A
- consist of rocks that are gently seaward sloping
- have an irregular surface
- overhanging rocks may collapse causing the cliff to retreat and the wave cut then lengthens
- allows waves to break at the foot of the cliff causing max erosion at this point
- found between high and low tide which causes friction for waves
19
Q
Caves/arches/stacks key points
A
- erosion takes place on a cliff face where there is weakness
- smaller hollows can be excavated to create caves
- where caves are created on either side of a headland and are eroded back they can meet each other and from an arch
- the sea is now able to splash under the arch further weakening and eventually the roof collapses leaving a stack
- over time the stack erodes into a stump
20
Q
Key points of sediment cells
A
- coastlines operate as sediment systems with sources, sinks, transfers, budgets and feedback mechanisms
- they seek a dynamic equilibrium
- sediment sources are rivers, the sea bed, erosion of the coastline and shell material
- there are 11 cells in England and Wales with some in sub-cells
- each cell is seperated by headlands or stretches of water
- sediment cells are a key component of shoreline management plans
21
Q
Positive feedback points
A
- sea walls may prevent flooding but they also limit cliff erosion
- this restricts the release of sediment into the system
- this sediment might otherwise have been re-deposited so helping to protect the coastline
22
Q
Negative feedback points
A
- sediment is eroded from a beach during a storm and is then deposited offshore to form a bar
- waves break before reaching the beach dissipating their energy and therefore reducing erosion of the beach
- normal wave conditions rework offshore deposits back to the beach
23
Q
Changes in sea level take place over the longer term due to …
A
- sea temperatures being colder or warmer than at present
- relative changes in levels of land
24
Q
Eustatic change…
A
- results from a fall in sea level due to a new glacial period when water is held as ice
- also results from a rise in sea leel when at the end of glacial period the ice on land melts
25
Isostatic change ,...
- arises from changes in local relationship of land to sea
- as ice collected on the land during glacial periods the extra weight pressed down on the land causing it to sink and sea level to rise
- as the land ice melts the land begins to move back up to its original position and the sea level falls
- depends on the thickness of the original ice and the speed of its melting
26
Emergent coastlines points
- falling sea levels expose land that is normally covered by the sea
- cliffs that are no longer being eroded become isolated from the sea, leaving fossil cliffs
- fossil features - eg - former caves are left higher up from the shoreline
- raised beaches occur as a series of sandy and pebble strewn terraces well above current sea levels
27
Contemporary change points
- the IPCC predicts that sea level could rise by 98cm by 2100 as a result of climate change
- sea level can change locally due to tectonic forces
28
What physical factors affect rapid coastal retreat?
- large destructive waves with a long fetch
- cliffs with structural weaknesses
- strong longshore drift
- cliffs vulnerable to mass movement and weathering as well as marine erosion
29
Human factors in rapid coastal retreat
- reducing sediment input by constructing dams on rivers
| - dredging sand and gravel from the sea bed
30
Rates are influenced by
- weather related factors - season type, storms, wind direction
- physical factors - relative hardness of rocks, rates of weathering
- human factors - coastal management schemes
31
Why are some coastal areas at high risk of flooding
- around estuaries or on deltas with very low altitudes
- subject to storm surges
- in delta regions so water comes from inland as well as the sea
- where protective mangrove forests have been cleared
- where rivers have been straightened to speed up river flow
- in areas where coastal topography funnels water from surges and/or high tides
32
Why is the number of environmental refugees likely to increase?
- rising sea levels
- more intense storms and secondary events
- coral reefs being attacked by bleaching
- salt water incursion into freshwater supplies
33
Hard engineering definition
a form of coastal management that involves the construction of man made features
34
Soft engineering definition
a form of coastal management that involves working with natural features
35
Conflict may come from coastal management from..
- managing natural resources to ensure long term productivity
- managing flood and erosion risk - relocation to safe areas
- monitoring coastal change
- educating communities to understand why change is needed
- creating alternative livelihoods before existing ones are lost
- adapting to sea level rise - relocating/building methods
36
What does intergrated coastal zone management require?
- recognition of importance of littoral zone to people's livelihoods as large numbers of people live and work at the coast
- recognition that management of a littoral zone must be sustainable - economic development should improve the QOL of people and this needs to be environmentally appropriate
- that an entire littoral zone is managed not just the narrow zone where waves cause erosion or flooding
37
Shoreline management plans points
- introduced in 1995
- don't exist in Scotland
- an approach to coastal management that involves all stakeholders in making decisions about how risks like flooding should be managed
- predict, so far as it is possible the way in which a coastline will be shaped in the future
38
What are the 4 coastal zone management policies?
- hold the line - maintaining level of protection
- advance the line - building new defences seaward
- no active intervention - no investment in defences
- managed realignment - allowing retreat of the shoreline
39
What does making a decision about which policy to use depend on?
- economic value of the land thats protected
- cultural and ecological value of land
- technical feasibility of engineering required
- the attitudes of and pressure from local communities
40
Why is the coastal erosion rapid in the developing world?
- inland dams reducing sediment supply and disupting local sediment cells
- rapid unplanned coastal development
- destruction of mangrove forests exposing coastlines
41
The general outcomes of this is...
- losers - farmers and fisherman with no legal claims to land
- winners - TNCs - eg - developers
