Coasts part 1 Flashcards
define system
a system of interrelated objects made up of components and processes that are connected together to form a working unit or unified whole
coastal landscape systems store and transfer energy and material on time scales that can vary
inputs to coastal systems
wave energy (kinetic) wind energy (kinetic) tidal energy (kinetic) material on slopes (GPE) material from offshore (GPE) energy from sun (thermal) urban planning coastal management/ defences
outputs of coastal systems
beach erosion by sea beach erosion by wind evapouration erosion of rock surfaces weathering/ erosion of cliffs
throughputs/ stores in coastal systems
beach sandbank near shore sand dunes longshore drift river sediments tidal energy (kinetic) build up of sand below water's surface
when does equilibrium occur on a beach
when sediment added is equal to that being taken away
inputs=outputs
dynamic equilibrium
negative feedback
system undergoes self regulationand changes in order to restore the equilibrium
occurs in a constanly changing system
define sediment cell
stretch of coastline and its nearshore area within which the movement of sediment is largely confined
generally a closed system
(england and wales)
what factors mean there is sometimes sediment transferred between cells
storm events
high tides
dominant winds
what divides up sediment cells
headlands (resistant rock)
topography
wind direction
tides
how many sediment cells are there
11
what are sediment budgets
a coastal management tool used to analyse and describe the different sediment inputs and outputs on the coasts, which is used to predict morphological (shape of coast) change in any particular coastline
do destructive or constructive waves have a bigger input
constructive
potential influences on coastal landscape systems of:
- waves
- winds
- tides
- geology
- global ocean currents
how are waves generated?
by the friction of wind dragging across the surface of water
the higher the wind speed and longer fetch then the more energy they have and bigger they are
what type of energy does a wave have?
GPE
as a result of its position above the wave trough,
kinetic
caused by the motion of water within the wave
formula for the amount of energy in a wave
P= (HxH) x T
P- power - kw/m
H- wave height
T - time between two wave crests (period)
crest
top of the wave
trough
bottom of the wave
wave length
distance between two crests or two troughs
wave height
amplitude- distance of crest to trough
what happens when waves reach the shore?
- the bottoms of the circulating molecules come into contact with the sea floor
- this causes friction which slows the wave down from the bottom
- this causes the wavelength to decrease and the waves start to bunch up
- the top of the wave is still travelling fast and the wave begins to steepen as the base lags behind
- when the depth is 1.3X wave length then the wave topples over, this is when the wave breaks
spilling waves
Steep waves breaking onto gently sloping beaches. Water spills gently forward as the wave breaks. As the wave approaches the shore, it slowly releases energy and the crest gradually spills forward.
Why? • Bottom of the ocean/beach is fairly flat • waves come in and slow down gently • steepen gently • and so break gently • top of the waves spill down the front
plunging waves
Moderately steep waves breaking onto steep beaches. The water plunges vertically downwards as the crest curls over and explodes on the trough. The air under the lip of the wave is compressed, and a crashing sound is often heard.
Why?
• When waves travel from deep water to shallow water very quickly
• and they slow down so fast start causes a motion of water that curls over and crashes down violently
surging waves
Low angle waves breaking onto steep beaches. The wave slides forward and may not actually break, as a result of the water being very deep beneath them.
Why?
• Don’t have much time to break because the transition from deep-water to shallow water is too fast
• So they end up just surging up onto the beach.
• Typically happens in may areas during high tide