The Coastal System
Question Answer
Name the inputs to a coastal system. Sediment and energy from wind, waves, tides and currents
Name the outputs of a coastal system. Sediments deposited further along the coast or inland
Name 4 flows and transfers of a coastal system. Erosion, weathering, transportation and deposition
Name 3 stores of a coastal system. Landforms such as beaches, dunes and spits
Coasts are open systems and are generally in ... ... dynamic equilibrium because the inputs and outputs are balanced
In a coastal system, a change in one input or output can cause ... ... negative feedback which restores the balance to the system
Give an example of negative feedback in the coastal system about cliff erosion. Beach is eroded -> cliffs are exposed to wave attack -> sediment eroded from cliffs is deposited on the beach ->
beach grows in size
Give an example of positive feedback in the coastal system about beach growth. Beach slows down waves -> more sediment is deposited -> beach grows in size -> beach slows down waves
Officially, how far inland does the coast go? 60 km
Officially, how far offshore does the coast go? 320 km
What percentage of the population lives within 100 km of the coast? 40%
What percentage of the population is less than 10m above sea level? 10%
Where is the backshore? From the high water foam lines to dunes, or the extreme inland limit of the beach
In what circumstances is the backshore affected by waves? In exceptional high tides and severe storms
Where is the foreshore? Between the high and low water mark
How is the foreshore affected by wave activity? Heavily influenced by marine activity and tides come in and out here
Where is the inshore? Between the low water mark and the point where the waves cease to have any influence on the land around them
Where is the offshore? The zone extending seaward from the point of low tide to the depth of wave-base level or outer edge of the
continental shelf
Where is the nearshore? Where waves steepen and break then reform in their passage to the beach and where they break for the last time
and surge up the foreshore
In the nearshore, much ... ... sediment is transported
Where is the swash zone? Where water action on the beach moves as water level varies
Where is the breaker zone? Where waves approaching the coastline commence breaking, which moves throughout the day
Typically, in what depths do waves break in? 5 to 10 metres
High energy coasts receive ... ... more inputs of energy from large, powerful waves
What are large powerful waves caused by? Strong winds, long fetches and steeply shelving offshore zones
Give some characteristics of high energy coasts. They tend to have sandy coves and rocky landforms like cliffs, caves, arches and stacks
On high energy coastlines, the erosion rate is ... ... higher than the deposition rate
Low energy coasts receive ... ... low inputs of energy from small, gentle waves
What are small, gentle waves caused by? Gentle winds, short fetches and gently sloping offshore zones
Where might you get gentle winds? In sheltered areas
Some coastlines are low energy because ... ... coral reefs or islands protect the coast from the full power of the waves
Give some characteristics of low energy coasts. They tend to have salt marshes and tidal mudflats
On low energy coastlines, the erosion rate is ... ... lower than the deposition rate
Give 5 inputs of sediment into a coastal system. Rivers, sea level rise, erosion, crushed shells of marine organisms and transportation
How do rivers input sediment into the coastal system? By carrying eroded sediment into the sea from inland
How does sea level rise input sediment into the coastal system? Flooding river valleys can form estuaries which then become a part of the coastal system
,Sediment can be inputted into the coastal system by the erosion of ... ... cliffs by waves, weathering and landslides
Sediment can be transported from offshore deposits from ... ... waves, tides and currents
What is the sediment budget? The difference between the inputted and outputted sediment
A positive sediment budget occurs when ... ... more sediment enters than leaves and the coastline builds outwards
A negative sediment budget occurs when ... ... more sediment leaves than enters and the overall coastline retreats
The coastline is divided into ... ... sediment or littoral cells
What are sediment cells? Sections of the coastline where overall, the balance between erosion and deposition is equal
Sediment cells are often split into ... ... sub-cells where there are specific inputs of materials whose transportation is then monitored
Clear boundaries mark sediment cells, such as ... ... headlands and rivers
Theoretically, sediment cells represent ... ... closed systems, so there is no transfer of material between cells
Coastal Energy Sources
Question Answer
How are winds caused? Air moving from high pressure to low pressure
Why are winds strong in storm events? The pressure gradient is high
Strong winds create ... ... powerful waves
What is a prevailing wind? Winds that blow consistently from the same direction
A prevailing wind, will cause higher-energy waves than ... ... those that change direction frequently
How are waves caused? Friction between the wind blowing over the surface of the sea, giving the water circular motion
How do waves break when approaching the coastline? Friction with the sea bed slows down the bottom of the wave and the top overtakes it, making an elliptical motion
The crest of the wave rises up ... ... and then collapses
The effect of a wave on a shore depends on ... ... its height
What can wave height be determined by? Wind speed, duration and fetch
What is fetch? The maximum distance of sea the wind has blown over to create the waves
What is a swash? Water washing up the beach
What is a backwash? Water washing back towards the sea
Constructive waves have ... ... a low frequency, and they are long and low
How many constructive waves do you get per minute? 6-8
The profile of constructive waves is more ... ... elliptical
Constructive waves have a powerful ... ... swash which deposits material on the beach
Destructive waves have ... ... a higher frequency and are high and steep
How many destructive waves do you get per minute? 10-14
The profile of destructive waves is more ... ... circular
Destructive waves have a powerful ... ... backwash which removes material from the beach
Destructive waves are most effective over ... ... steeply shelving seabeds which cause a rapid increase in friction and a steep wave front
In any area, waves usually predominate as either ... ... constructive or destructive
What is wave refraction? The bending of waves due to varying water depths underneath
How do waves refract? Part of a wave in shallower water slows down compared to the part in the deep water, causing the wave to bend
Wave refraction particularly occurs when a wave approaches the shoreline at ... ... an angle, so part of the wave crest is in shallower water and the other part is in deeper water and it bends
towards the beach
What is a rip current? Waves retreating by finding a divet in the seabed and going under the waves behind it
, What are tides? The periodic rise and fall of the ocean surface
What are tides caused by? The gravitational pull of the moon and sun
Tides affect the ... ... position waves break on the beach
High tide means waves will go ... ... further up the beach
Most landforms are created and destroyed in the area between ... ... maximum high and low tide- the foreshore
Talbot Bay in the Australian West Coast has ... ... one of the largest tidal changes in the world
By how much can the tide in Talbot bay rise? 10.8 m
Spring tides occur when the ... ... sun, moon and earth are aligned and a gravitational pull creates a large tidal range
When does a low spring tide occur? After a new moon
When does a high spring tide occur? After a full moon
How often do spring tides occur? Twice a month
Neap tides occur when the ... ... sun and moon are perpendicular so there is a smaller gravitational pull on the tide which creates a low tidal
range
A tidal bore is a phenomenon where ... ... the leading edge of the incoming tide forms a wave of water that travels up a river or narrow bay against the
direction of the river or bay's current
What are currents? The general flow of water in one direction
Currents move material ... ... along the coast
Give 3 things currents can be caused by. The wind, variations in water temperature or variations in salinity
What are estuaries? Where a freshwater river and ocean meet
Water continuously ... ... circulates in and out of an estuary
In an estuary, tides create the biggest flow of ... ... saltwater
In an estuary, rivers create the biggest flow of ... ... freshwater
Estuarine sea currents happen when ... ... dense seawater sinks and moves near the bottom
Anti-estuarine currents happen when ... ... less dense freshwater from rivers flow into the estuary and are strongest near the surface of the water
Why are anti-estuarine currents warmer than estuarine currents? They are heated by the sun
The earth tries to balance out the heat the equator gets from the sun through ... ... currents running to the poles
The spin of the earth causes currents to ... ... change direction slightly
When forming a current, why is there a circular motion effect? Warm water rises and cool water descends
At the end of the Last Ice Age, what turned off the Gulf Stream Pump? Freshwater from the Great Lakes of North America
What did the Gulf Stream Pump turning off do to Europe? Send it into an ice age
What is downwelling? When cold land causes cold currents to sink and warm water to rise further away, and then be drawn back to land
Downwelling can be seen as a ... ... conveyor belt system
What is upwelling? When warm water near warm land is pushed away by surface winds and then deep, cold, nutrient rich water rises
to replace this
Why are areas of upwelling good fishing grounds? Phytoplankton can breed there
Describe the usual currents between Australia and South America. Cold water along the S.A. coast flows westward towards Australia by equatorial winds
What is the El Niño phenomenon? Where easterly winds weaken and warm water moves eastward from Australia to S.A.
The El Niño phenomenon gives the USA a ... ... warmer winter
The La Niña phenomenon is the same as El Niño, but ... ... in the Northern Hemisphere between Japan and the USA
Coastal Processes 1
Question Answer
