Coast Landscapes and Change Flashcards
How is a wave created
2B.4
created through friction between the wind surface, transferring energy from the wind into the water
what is a wave
2B.4A
transfer of energy from one water particle to its neighbour with individual water
what is wave height
2B.4A
vertical distance from the peak to trough
how is wave height determined
2B.4A
energy transfer from the wind and water depth
what is wave length
2B.4A
horizontal distance from crest to crest
what is wave frequency
2B.4A
number of waves passing a particular point over given period of time
waves in a open sea
2B.4A
- waves are simply energy moving through water
- water itself only moves up and down not horizontal
- there is some obital water particle motion within the wave but no net forward water particle motion
what does wave size depend on
2B.4A
wave fetch -
wave depth
strength of wind
duration of wind blows
how does a wave break
2B.4A
waves reaching shore reach a wave depth 1/2 their wavelength the internal orbital motion of water within the wave touches the sea bed
Wave particle is distorted due to friction between the sea bed, this slows down the wave
- wave depth decreases further, wave velocity slows wavelength shortens and wave height increases.
- wave crest begins to moe forwards much faster than the wave trough
- wave crest outruns the trough and wave topples forwards
wave breaks in the nearshore zone and water flows up the beach as swash
wave losses energy and gravity pulls the water back down the beach as backwash
Constructive Waves
2B.4A
low energy waves low flat wave height long wavelength low wave frequency (6-9 per minute) strong swash - pushes sediment up the beach but weaker backwash can't transport all particles back - backwash into beach material
Destructive Waves
2B.4A
high energy waves
large wave height
short wavelength
high wave frequency
strong backwash weak swash due to steep angle of impact = energy directed downwards and backwards
strong backwash erodes material from top of beach
what is beach morphology
2B.4A
shape of the beach
what is a beach sediment profile
2B.4A
pattern of distribution of different sized or shaped deposited material
how do constructive waves effect beach morphology
2B.4A
net movement of sediment up the beach steeping the beach profile
Produce berms at the point where swash reaches high tide line
swash carries sediment of all sizes up the beach but weaker backwash can only transport smaller particles down the beach = larger heavier shingle at back of beach and sand closer to ocean -> backwash flows down beach loses energy through friction = sediment further sorted = fine sands closest to sea - coarser sands deposited in middle of beach
what is a berm
2B.4A
ridge of material across the bridge
how do destructive waves effect beach morphology
2B.4A
- beach gradient reduced due to weak swash and powerful backwash which produces sediment down the beach
- some sediment thrown forwards by strong waves
- large pebble sized sediment dragged down the beach by backwash to form wide ridge of material below
- friction could cause backwash to down some sediment on middle or lower beach = deposited size sediment decreasing towards sea
Decadal Variation - Beach Morpholgy
2B.4A
Climate change is expected to produce more extreme
weather events in the uk
winter profiles may be present for longer time over course of year
more frequent powerful destructive waves reduce beach size = high tides to reach inland = rate of erosion increase
Monthly Variation - Beach Morphology
2B.4A
Highest tide occurs every 2 months at spring tide - two very low high. tides
As months progress from spring down to neap tides - lower high tides produce series of berms at lower and lower points down the beach
Berms destroyed as material pushed further up beach - once a neap tide passes and moves towards next spring tide
Daily Variation
2B.4A
Destructive waves from storms in summer reshape beach
Constructive waves = calm conditions in winter
Wind Drops = destructive waves -> constructive waves
Storm beaches = result from high energy deposition of sediment from sever storms
what does energy transferred from the wind depend on
2B.4A
wind strength
wind fetch
uninterrupted distance upon water over which wind blows over
wind duration
how are sea waves produced
2B.4A
winds currently blowing in local area - vary in height and direction
what happens when the wind drops
2B.4A
wave energy continues to be transfers across ocean in the form of swell waves
Swell Waves
2B.4A
absorb smaller sea waves and gain energy and height as they travel
travel long distances before they lose energy
produce waves at coast even with no wind
can form periodically larger waves amongst smaller
Name the 4 erosion processes
Hydraulic Action
Corossion
Abrasion
Attrition