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
tidal bulge
- 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
alignment strongest vs weakest
- 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
interaction perigean
- 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
Trinidad coastline part 1
- 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
Trinidad coastline part 2
- 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
economic losses
- 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
Environmental losses
- 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
social losses
- 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
Recession rates influenced by geological factors as well as
wind direction, fetch, tides, seasons and wearer systems and storms which determine wave intensity.
