Lesson 11 Flashcards
What is coastal retreat?
the coastline retreating
Natural factors causing the coastline to retreat? (2)
geology of coast
marine and sub Ariel processes
What is the most rapid rate of coastal recession? (5)
weakly consolidated rock large destructive rocks submergence of a coastline large scale mass movement constant weathering
Human factors that influence coastal retreat? (2)
sea wall/groynes - stop erosion in certain place but continues further down
beach replenishment - can’t happen as sediment isn’t carried (stopping deposition) bigger waves erode further as beach isn’t built up
What is offshore dredging?
dredging for sand and gravel for construction purposes (under UK government licence)
How does offshore dredging cause problems? (2)
Less sediment to absorb wave energy so erosion rates increase.
Deeper water means waves have more power so they’re more destructive
How does dreading of shallow seabeds have a negative impact on the environment? (2)
removing species and communities
increasing sediment levels - damage coral reefs
What impact can increased deposition have? (3)
raise sediment levels
may affect sea level rise
isostatic sinking
What impact can increased deposition have locally? (2)
local sea currents altered - waves larger
effect sediment balances and erosion
What evidence is used?
computer modelling rather than measured data
Example of human activity and coastal recession?
Lowestoft, resulted in beach loss
How is the Nile delta facing retreat?
significant erosion on half of it
Reasons for erosion on the Nile Delta?
salt intrusion due to sea rise and coastal flooding more frequent (due to climate change) - land loss
How has Aswan dam effected the Nile Delta?
reduced sediment supply
How do weather systems cause coastlines to retreat? (2)
high pressure (anticyclones) bring calmer conditions, smaller waves. Low pressure (depressions) has a mixture of air masses at different temperatures.
How does low pressure influence coastal retreat?
Air rises rapidly, strong winds anticlockwise creating larger waves.
How does cold weather influence coastal retreat?
In winter the difference between the equator temperature and pole is greatest so depressions are strongest. Low pressure and fast speeds create destructive waves, more recession
How does hot weather influence coastal retreat?
global warming added more heat to atmosphere, intensified low pressure systems. Erosion increase in winter
How many tides does the UK experience a day?
2 high + 2 low
When do high tides occur?
(spring) sun and moon aligned - gravitational pull strongest.
When do low tides occur?
(neap) sun and moon at right angles - gravitational pull weakest. Occur twice every lunar cycle.
What do tides determine?
When water will reach the shore
What happens at high tides?
Waves more likely to reach the back shore and erode land faster. Combined with destructive storm waves erosion is at max
What does wind direction determine?
wave direction. Prevailing dominate
