C -> 2.10 - 2.13 Flashcards
1
Q
west africa
A
- 700m of erosion in 40 years, particularly in NW guinea-bissau
- 10cm of SLR since 1950, 1m by 2100
- urbanisation high along coast
- fishing, tourism, commerce
2
Q
rising sea level guinea
A
- 10cm since 1950
- 1metre by 2100
- $1.7 billion of loss for airlines
3
Q
Coastal management Guinea
A
Added groynes, but ineffective as one end was not replenished, exacerbated this ends recession.
4
Q
sand extraction guinea
A
- removed from river
- used for housing
- sediment not transported to coastline
5
Q
mangrove deforestation
A
- used for fuel wood
- to smoke fish
- for fuel supply
6
Q
diamond mining
A
- gravel extracted from rivers
- diamonds retrieved
- gravel (sediment) not always returned
7
Q
rock hardness
A
- softer and uncemented sediment and rock are vulnerable to cliff retreat
- igneous rocks have a stronger crystalline structure where joints and fractures in the rock result in more complex coastal landforms
8
Q
geological orientation
A
- discordant coasts have different rates of erosion, resulting in headlands and bays
- headlands refract waves to concentrate wave energy, resulting in more complex erosional features
9
Q
wave type/ energy
A
- water is driven into the cracks in rocks, compressing air that is already there, creating an explosive blast
- bombardment and blasting is made worse by sediment thrown up in waves
10
Q
rock breakdown/ erosion
A
- eg, hydraulic action/ attrition/ abrasion, often together with other subaerial
- some mechanical processes (solution and salt) expose the coastline to wave and subaerial processes
11
Q
rock layers
A
- differences within cliff face affects level of resistance, different rates of erosion, and over time cause landslides
12
Q
wave cut erosion
A
- worn back cliffs leave shore (wave cut) platform, which cam be covered by the sea at low tide, resulting in further abrasion, limestone solutions and marine organisms creating a rocky foreshore (e.g. Glamorgan Heritage Coast)
- as platform becomes longer, wave attack on cliff base will decrease
13
Q
offshore dredging
A
- removing material for ports/ beach nourishment
- deep water, energy retained
14
Q
sea defences lead to
A
- interruption of sediment transfer (longshore drift)
15
Q
Egypt: CC impacts
A
- flooding of Alexandra
- 10% of nile delta flooded
- 7 million people displaced
- farming - less food, famine
- erosion of delta: SLR and more frequent storms, 5m/yr retreat
- water conflict
- cost of sea defences and loss of farmland
16
Q
threat to mappleton
A
- approx 50 properties and B1242 access road
- soft boulder clay cliffs
- fetch from Scandinavia
- 1-2m/yr rate of erosion
17
Q
the decision (1991)
A
- a coastal management scheme costing 2 million was introduced
- two types of hard engineering
- Norwegian granite rock armour along the base of the cliff
- built two rock groynes
- stopped beach material being moved south from Mappleton along the coast
- left withensea unprotected
18
Q
impact of the decision
A
- Mappleton and the cliffs are no longer at great risk from erosion
- this has increased erosion south of Mappleton
19
Q
west africa coastal stats
A
- 31% pop.live in coastal areas - 105 million
- 500k impacted by coastal floods annually
- 1.5 billion estimated cost of coastal protection
- 11bn expected annual damage from coastal floods by 2050s
- 296 million cost of degradation in Togo due to erosion and associated economic opportunity losses
20
Q
overall basic principle of erosion
A
rate of cliff retreat depends on amount of contact time between sea and rock
21
Q
fetch
A
- distance that waves travel uninterrupted
- longer fetch = faster retreat
22
Q
wind direction
A
- largest waves from prevailing wind direction - SW in south wales
23
Q
depressions
A
- low pressure weather systems
- more intense, faster wind speeds
- large destructive
24
Q
anticyclones
A
- high pressure
- calmer conditions
- smaller waves
25
Q
tidal bulge
A
- earth rotates on axis once every 24 hours
- moon has gravity attraction - waves are pulled causing a bulge
- laws of inertia counter act this, so bulge on opposite side of earth
- bulges are aligned with moon as earth rotates
26
Q
alignment strongest vs weakest
A
- once a month (every 2 weeks)
- spring high tides happen when sun + moon aligned, so pull is strongest
- lowest high tides are NEAP tides, when sun and moon at right angles - weakest gravitational pull
27
Q
interaction perigean
A
- the moon takes 1 month to rotate around the earth
- rotation is elliptical, which means it sometimes closer to the earth than others, and when closer, the gravitational effect is stronger
- 4 times a year, this proximity coincides with the spring high tide, so you get an even higher spring tide (perigean spring tides)
28
Q
Trinidad coastline part 1
A
- small islands developing state (SID) - low lying and susceptible to current 0.06 m/yr rise in SL
- 70% population live or work on coast
- winter storms (nov-apr) from Atlantic have higher swell waves - affecting north and east coasts
- NE-SW wind direction means east coast beaches are subject to southerly LSD - and subsuequently have highest erosion rates - esp. Coco Bay and Guayaguayare Bay (0.63m/yr)
29
Q
Trinidad coastline part 2
A
- coastal flooding along 20km of Manzanilla Beach in 2014 cuts off routes to SE (300m destroyed)
- geology is mix of low grade metamorphic rocks, and weak sandstone and alluvium deposits
- Mayaro is largest coastal development (community) - but Guayaguayare vital site of oil industry - main source of GDP and exports
30
Q
economic losses
A
- T&T is 3rd economy in Americas after US/CANADA - heavy depend on petrochemical industry of east coast(40% GDP,80% exports)
- all major natural gas pipelines come ashore at Guya. site to serve rest of country (site of greatest erosion)
- owing to lower economies of scale, infrastructure losses to erosion are more severe for SIDS
- Manzanillo beach flood 2014 destroyed 300m of major access road - £5m cost
- many luxury homes in Mayaro 700k+
- 400k+ tourists visited last year
31
Q
Environmental losses
A
- nesting sites for endangered leatherback turtles along north and east coast beaches - ecotourism
- 16k acre trinity hills wildlife sanctuary and reserve on south coast has wealth of flora and fauna
- ecosystems thought to adapt to small incremental changes of coastal erosion - so impact is smaller?
32
Q
social losses
A
- potential loss of coconut plantations which dominate east coast - also home to watermelon and vegetable cash crops (RISK: livelihood for inhabitants)
- transport/ access affected by road damage during 2014 flood - RISK: commuters ant access oil and tourists industries
- value of luxury coastal property likely to decrease over time with increased erosion rates - cost of relocation and break up of community more damaging for poorer locals
- RISK: potential damage to existing hotel and tourist industry, eg Manzanillo beach facility
- social tensions created by individual management attempts upstream which block LSD sediment
33
Q
Recession rates influenced by geological factors as well as
A
wind direction, fetch, tides, seasons and wearer systems and storms which determine wave intensity.
