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EQ3 - Coggle Diagram
EQ3
Causes of coastal flooding
coastal recession
physical factors that cause coastal recession
Geological:
softer, weaker rock more easily eroded - rocks with geological weaknesses more easily exploited by erosional processes
rocks dipped towards sea are less stable, so more vulnerable to mass movement
Subaerial:
material that is loosened by weathering is more vulnerable to mass movement e.g. blockfalls of material loosened by freeze thaw can occur, leading to cliff retreat
heavy rainfall can also trigger landslides
Marine:
destructive waves that break at the foot of cliff have more energy to erode
high energy waves created in high winds and with long fetches, have more erosive power
narrow beach will be unable to dissipate wave energy as well as wide flat beach
wave refraction will cause wave energy to be concentrated around headlands and dissipated in bays.
Human factors that impact recession
Dredging:
mining of sediment from nearshore creates a pit which will be infilled by sediment within coastal system
removes more sediment from the beach and can increase rates of erosion
Coastal management:
coastal defences e.g. sea walls can deflect power of destructive waves + protect coastline from erosion
groynes can trap sediment transported by longshore drift, can also prevent sediment from moving downdrift, leading to sediment starvation, a narrow beach + increased coastal erosion
Factors influencing rates of recession
Short term
Wind direction:
wind that is blowing onshore will create waves that attack the coastline
Fetch:
a long fetch will increase the wave height shorten the wavelength, and increase the wave energy
Weather systems and storms:
low pressure weather systems can create storm conditions which increase wind strength and wave energy
Long term
Tides:
during high tide the rate of recession is increased as waves can reach the back shore
Seasons:
winter tends to have more storms which are more likely to increase rates of recession
Local factors influencing coastal flood risk
Future sea level rise, particularly for low-lying areas, at risk of becoming uninhabitable in future
Places higher and well above sea level have lower risk
Removing vegetation, can destabilise landforms e.g. sand dunes, destroy ecosystems e.g. mangrove forests, both provide natural protection from flooding
Human activity,e.g. extraction of groundwater, can lead to land subsidence, increasing vulnerability to flooding
Storm surge events
short term increases in sea level, can be caused by depressions + tropical cyclones
low air pressure 'pulls' sea level up
strong winds create large waves + push water towards the coast
Climate change
may increase flood risk
scientists believe frequency of tropical storms will decrease, but frequency of more intense storms will increase in some areas
scientists almost certain mean global sea levels will continue to rise
likely rise by 2100 is uncertain, depends on level of future greenhouse gas emissions
Sea level change
Causes of sea level change
Eustatic:
global change in the volume of water in the ocean
as temp increase, ice stored in ice sheets and ice caps melts, and sea level rises
during glacial periods more water was stored on the land in solid ice form, sea levels fell
Isostatic:
local change in the land level, leading to relative change in sea level
land can subside due to weight of the ice stored on it, leads relative sea level rise
land once covered in ice is still rising and falling in a process called glacial isostatic adjustment
high rate of deposition may increase level of land leads to relative sea level fall
tectonic processes can displace ocean and lead to sea level change
Effects of long term sea level change
Emergent coastlines:
formed when sea levels fall
raised beaches are found higher than the current sea level
fossil cliffs are often found at the back of raised beaches and were formed by erosional processes before sea levels fell
emergent landforms are affected by subaerial processes
Submergent coastlines:
formed when sea levels rise
rias are formed when V-shaped valleys are flooded and submerged
Fjords are formed when U-shaped valleys are flooded and submerged
Dalmantion coastlines formed where geological folds run parallel to the sea on a concordant coastline and sea levels rise, flooding valleys of the folds + leaving narrow islands
Contemporary sea level change
scientists believe global warming is leading to increase in global mean sea level
predicted sea level could rise by 0.43-0.84 m by 2100
low lying coastal communities and SIDS becoming increasingly vulnerable to coastal flooding + erosion
coastlines with frequent tectonic activity also at risk
Impacts of coastal flooding
consequences of coastal recession and flooding
Economic losses:
properties + businesses can be completely destroyed by cliff collapse or flooding
possessions of residents lost or damaged
homeowners may find themselves in negative equity as properties at increasing risk will lose their value
agricultural land can be lost to flooding
transport infrastructure is at risk
Social losses:
recreational uses of the coastline are affected when beaches and facilities disappear
social + political tensions can arise over how to manage or cope with risks
wellbeing of community can be affected as people forced to relocate
businesses/ agricultural land that is destroyed affects people's livelihoods
areas can become less attractive to locals + tourists when infrastructure is at risk or destroyed
Economic + social consequences of coastal flooding + storm surges
Developing country - Mozambique:
March 2019 Cyclone caused 4.4m high storm surge
one of lowest income countries in the world, GDP per capita of US$491
caused flooding up to 6m in depth
over 600 deaths, more than 11,000 properties + 700,000 hectares of crops were destroyed
outbreaks of waterborne diseases
cost of damage + disruption to economic activities estimated at US$3 billion
Developed country - UK:
December 2013 largest storm surge to hit East coast of UK in 60 years
homes collapsed into the sea as high tides eroded cliff beneath
10,000 homes evacuated
three injuries
720 commercial + residential properties flooded
total economic cost to England and Wales from flooding west £1000 to £1500 million between Dec 2013 + March 2014
Environmental refugees
forced to leave homes as effects of climate change put more coastal communities at risk from flooding + storm surges