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Geography A-Level > Coasts > Flashcards

Coasts Flashcards

1
Q

Local factors increasing flood risk on some low-lying and estuarine coats. What are those local factors?

A
  • height of land above sea level
  • vegetation removal
  • land reclamation
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2
Q

Local factors increasing flood risk on some low-lying and estuarine coats.
Local factors and evidence

A

Height of land above sea level:

  • highest point in Maldives is only 2.3m above sea level
  • 60% of Bangladesh is less than 3m above sea level
  • most of Kiribati’s population live on Tarawa island where max height above sea level is 3m

Vegetation removal:

  • Java
  • a 100m belt of mangrove forest = decrease wave height by 40%
  • a 1km belt = decrease storm surge height by 0.5m

Land reclamation:

  • 26% of Netherlands is below sea level
  • Amsterdam is 2m below sea level
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3
Q

Local factors increasing flood risk on some low-lying and estuarine coats.
What further increases this risk?

A

Global rising sea levels

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4
Q

Local factors increasing flood risk on some low-lying and estuarine coats.
Evidence of global sea level rise and impacts

A

Bangladesh = a 40cm^ in sea level = 11% submerge = 7-10m environmental refugees

Maldives = a 50cm^ in sea level = 77% submerge

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5
Q

Define storm surge

A

A temporary, local rise in sea level produced when a depression, storm or tropical cyclone reaches a coast.

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6
Q

LIC case for storm surges

A

Bangladesh 2007:
- category 4 cyclone, 6m storm surges

impact worsened by:

  • funnel shape of Bay of Bengal
  • coastline made of unconsolidated sediment = easily eroded
  • mangrove removal
  • 60% is below 3m^ sea level

impacts:
- 15 000 died
- 1.6m homes destroyed
- 900 fresh H2O tube wells destroyed

BUT is an improvement from the 1970 cyclone where 300 000 died because:
warnings and embankments improved

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7
Q

HIC case for storm surges

A

UK 2013 storm w a 3-6m storm surge

impacts worsened by:
- funnel shape

impacts:
- 2 deaths
- 1 400 homes flooded

BUT better than 1957 storm where 307 died because:

  • flood defences were improved eg. Thames Barrier which protected 800 000 homes
  • forecasts improved + efficient evacuation plans
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8
Q

The importance of mangrove forests

A
  • a 100m belt = reduce wave height by 40%
  • a 1km belt = reduce storm surge height by 0.5m
  • 2004, Indian Ocean Tsunami: a village had 6 000 deaths w no mangroves VS 2 deaths w mangroves just adjacent
  • stabilises + traps sediment = raising height of land above sea level
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9
Q

Economic losses from coastal recession in HIC

A
  • residential land can vary from £500k to £2.1m
  • re-routing a road can cost between £150-250k per 100m
  • collapse of the section of coast supporting South Devon Main Line Railway in Feb 2014 cost £35m to repair + businesses in the South West lost £60m
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10
Q

The issue with coastal erosion in the UK

A
  • there is very little help for those who lose their homes
  • there is no national compensation scheme

BUT the UK has ‘Coastal Change Pathfinder’ who gave the East Riding of Yorkshire £1.2m + funded relocation and demolition of 43 homes

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11
Q

Evaluating the social and economic losses in HIC

A
  • erosion rates are slow and local NOT in Holderness coast (120m coastal retreat in the last century)
  • areas of high density populations have coastal defences
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12
Q

Social losses/ impacts of coastal recession and flooding

A 
Relocation: 
- break up of community 
- stressful 
Loss of livelihoods: 
- financial issues: loss of income, finding new jobs
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13
Q

Coastal flooding and storm surge events can have serious economic and social consequences for coastal communities in HIC/ developed

A

Australia - a 1m rise would:

  • flood 75 hospitals
  • flood 116k homes costing $72b
  • decrease coral reefs = decrease tourism (nearly 1m per year)

North Sea flood UK 2013

  • all rail services canceled in Scotland
  • 40k homes lost power
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14
Q

Coastal flooding and storm surge events can have serious economic and social consequences for coastal communities in LIC/ developing

A

Philippines - a 1m rise would:

  • cause fishing industry to lose nearly $200k
  • affect 60% of Manila (capital city)

2013 Typhoon Haiyan:

  • 90% Tacloban impacted
  • population of high density
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15
Q

Transportation processes and explain each

A
  • traction: large boulders/pebbles rolling along the sea bed
  • saltation: lighter sediment bouncing along
  • suspension: very light sediment carried aloft in water/air
  • solution: dissolved sediment carried in water
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16
Q

Sediment transportation is determined by

A
  • angle of wave attack
  • longshore drift
  • current
  • tides
17
Q

Sediment transportation. Explain direction/angle of wave attack

A

​- main determinant of the direction of sediment transport (in the foreshore zone)

  • wind is blowing directly onshore, the incoming swash transports the material direction up the beach at 90’ to the coastline
  • backwash then transports sediment perpendicularly back down to the beach to its original starting position
  • sediment is moved up and down the beach, but there is no net lateral movement.
18
Q

Sediment transportation. Explain long-shore drift

A

This is the net lateral transport of material along the coastline when waves approach the coast at an angle.

Incoming swash transports sediment up the beach at an angle (movement contains an up-beach component and a lateral component).

Gravitational backwash then transports sediment back down the beach at 90’ to the coastline.

A sediment particle comes to rest some distance along the beach from the original starting point due to net lateral movement.

Particle moves in a zig-zag fashion along the beach with each incoming wave.

19
Q

Sediment transportation. Explain currents

A

This is the flow of water in a particular direction, and they can transport sediment in the nearshore and offshore zones.

They can be driven by winds, or initiated by differences in water density, temperature or salinity.

​Currents transport sediment over a variety of spatial and temporal scales:

The global thermohaline circulation connects four oceans and takes 500 years for one complete circuit.

Rip currents on the beach transport sediment a few metres out to sea for a few hours when the wind is blowing direcly onshore with the right strength.

20
Q

Sediment transportation. Explain tides

A

Tides are changes in sea level produced by the gravitational pull of the moon and the Sun.

The incoming and ebbing tide can create tidal currents in the nearshore and offshore zones that transport sediment.

21
Q

Explain formation of sand dunes

A
  • in low relief
  • low energy waves w strong swash, depositing sediment which builds up the coastal plain landscape
  • created through sediment transportation and deposition
  • wind encounters obstacle and velocity falls, depositing sediment
  • sand/ sediment gets trapped on obstacles (eg. rock or wood) on the beach = embryo dune
  • tough plants like MARRAM grass take root in the dune and the roots help stabilize the sand in place
  • plants die and add nutrients to sand dune improving soil, developing even more vegetation
22
Q

What can be found in sand dunes? Explain how it is formed

A
  • dune slacks

- formed by wind erosion

23
Q

Explain the importance of vegetation in stabilizing coastal landscapes

A
  • they allow flocculation which is the binding of sediment together in bigger clusters making them stay put where they are as they become heavier and harder to be transported and eroded by wind or water
  • wind reaches vegetation, reducing velocity forcing sediment deposition
  • pioneer plants provide nutrients allowing marram grass to colonize
  • marram grass has waxy leaves reducing wind blown sand abrasion

Geography A-Level (4 decks)

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