Coastal Environments- Advanced physical paper 3
Coastal System
Factors affecting the coastline
Marine factors: Human factors:
-Wave action -Coastal settlements
-Long shore drift -Recreation and tourism
-Currents -Port construction
-Tides -Farming and land reclamation
-Sand and gravel extraction
-Pollution and coastal management
Waves
Waves are the movement of energy through the water and caused by the frictional drag of
wind blowing across the surface of the sea.
Affected by:
-Wind speed
-Fetch, the distance over which the wind has blown
-Gradient of the beach and shelf area
The biggest waves can blow in the Southern Ocean, at 40 to 60 degrees South, the fetch is
great and only a small bit of South America reducing the fetch. 23m waves recorded of the
Coast of NZ large HA on cliff face. Smallest waves occur around the Equator, low wind
speeds, limited fetch length bc of landmass obstruction.
Waves move in the direction of the winds that created them.
The wave form moves. Water particles rotate in a circular/ elliptical direction as the wave
passes through. It is a movement of energy. Until the waves breaks and then the water is
transported towards the shore.
Wave length is the distance between two wave crests.
Wave steepness= wave height/ wave length
Wave energy is related to wave height
The plunge line is the point when the wave breaks
,Swash is the body of foaming water that rolls up the beach when a wave breaks. It gets it’s
energy from the energy released by the breaking wave.
Backwash is the water that returns down the beach after a wave has broken.
Types of waves
Wave moves into shallow water, (depth of water is less than half the wavelength,) slower
wave due to friction with the sea bed. Reduced velocity, compresses the waves and reduces
the wavelength and increases the wave height. The movement of water particles becomes
elliptical instead of circular. The base of the wave slows down compared to the crest of the
wave, the wave steepens and breaks.
Energy dissipated as friction of swash against beach. Absorbed by gently-sloping beach.
Gentle sloping beaches protect the coastline from erosive effects. Waves against cliffs and
sea walls cause the energy to be directed to vertical surfaces.
Destructive energy waves
Remove sediment from the beach. Steep, high waves, shortwave length, high wave height.
High wave frequency, (over 10 waves per minute.) Often are storm waves driven on the
beach by strong onshore wind. As they break they crash onto beach and much of the water
is returned back into the sea, instead of rushing up the beach. Wave crests are close
together.
Built up sediment from backwash, forms longshore bars near the low tide mark.
High energy waves
Strong winds from the ocean directly to the coastline will produce storm waves. Storm
waves break on steep sloping beaches and form plunging breakers, with a steep crest. They
break and fall vertically onto the beach.
Constructive waves
Add sediment to beach. Long wavelength, far apart crests and low frequencies, (under 8
waves per minute.) Break and spill up sediment onto the beach with a weak backwash. They
form berms at the top of beaches.
Low energy waves
,Wind strength dies down over the ocean, and wave movement continues, they have less
high than high energy waves. They reach the shore as gentle swell waves. The wave spills up
the beach as spilling breakers.
Wave refraction
At irregular coastlines, e.g headands and bays, waves are refracted. There is sea bed friction
by the headland and shallower water. Waves are higher and steeper and break earlier.
Waves headed from the bay area lose velocity less rapidly and have a lower wavelength.
Orthogonals are lines drawn at right angle the wave crests and show wave energy being
concentrated at headlands and the erosive power. Orthogonals converge at headlands,
creating high erosion and diverge at bays.
Refraction from the headland causes longshore currents of sediment to be moved into the
bays forming bay beaches.
Tides
Caused by gravitational pull of the moon, sun and earth in orbit.
What causes a high and low tides?
The moon draws water to the side closest to it creating a ‘bulge’, because of gravitational
pull. Note on the opposite side, centrifugal force, causes a high tide.
There is a repel of water on the other sides causing low tides.
What causes the highest high tides and the lowest low tides?
The alignment of the moon and sun (creates strongest force). The sun enhances the moon’s
gravitational pull.
Tides with the greatest range are known as springs.
Neap tides are seven days after springs. Occurs between 2 spring tides. The moon and sun
are at 90 degrees to each other. It is a period of moderately lower tides.
,
Coastal System
Factors affecting the coastline
Marine factors: Human factors:
-Wave action -Coastal settlements
-Long shore drift -Recreation and tourism
-Currents -Port construction
-Tides -Farming and land reclamation
-Sand and gravel extraction
-Pollution and coastal management
Waves
Waves are the movement of energy through the water and caused by the frictional drag of
wind blowing across the surface of the sea.
Affected by:
-Wind speed
-Fetch, the distance over which the wind has blown
-Gradient of the beach and shelf area
The biggest waves can blow in the Southern Ocean, at 40 to 60 degrees South, the fetch is
great and only a small bit of South America reducing the fetch. 23m waves recorded of the
Coast of NZ large HA on cliff face. Smallest waves occur around the Equator, low wind
speeds, limited fetch length bc of landmass obstruction.
Waves move in the direction of the winds that created them.
The wave form moves. Water particles rotate in a circular/ elliptical direction as the wave
passes through. It is a movement of energy. Until the waves breaks and then the water is
transported towards the shore.
Wave length is the distance between two wave crests.
Wave steepness= wave height/ wave length
Wave energy is related to wave height
The plunge line is the point when the wave breaks
,Swash is the body of foaming water that rolls up the beach when a wave breaks. It gets it’s
energy from the energy released by the breaking wave.
Backwash is the water that returns down the beach after a wave has broken.
Types of waves
Wave moves into shallow water, (depth of water is less than half the wavelength,) slower
wave due to friction with the sea bed. Reduced velocity, compresses the waves and reduces
the wavelength and increases the wave height. The movement of water particles becomes
elliptical instead of circular. The base of the wave slows down compared to the crest of the
wave, the wave steepens and breaks.
Energy dissipated as friction of swash against beach. Absorbed by gently-sloping beach.
Gentle sloping beaches protect the coastline from erosive effects. Waves against cliffs and
sea walls cause the energy to be directed to vertical surfaces.
Destructive energy waves
Remove sediment from the beach. Steep, high waves, shortwave length, high wave height.
High wave frequency, (over 10 waves per minute.) Often are storm waves driven on the
beach by strong onshore wind. As they break they crash onto beach and much of the water
is returned back into the sea, instead of rushing up the beach. Wave crests are close
together.
Built up sediment from backwash, forms longshore bars near the low tide mark.
High energy waves
Strong winds from the ocean directly to the coastline will produce storm waves. Storm
waves break on steep sloping beaches and form plunging breakers, with a steep crest. They
break and fall vertically onto the beach.
Constructive waves
Add sediment to beach. Long wavelength, far apart crests and low frequencies, (under 8
waves per minute.) Break and spill up sediment onto the beach with a weak backwash. They
form berms at the top of beaches.
Low energy waves
,Wind strength dies down over the ocean, and wave movement continues, they have less
high than high energy waves. They reach the shore as gentle swell waves. The wave spills up
the beach as spilling breakers.
Wave refraction
At irregular coastlines, e.g headands and bays, waves are refracted. There is sea bed friction
by the headland and shallower water. Waves are higher and steeper and break earlier.
Waves headed from the bay area lose velocity less rapidly and have a lower wavelength.
Orthogonals are lines drawn at right angle the wave crests and show wave energy being
concentrated at headlands and the erosive power. Orthogonals converge at headlands,
creating high erosion and diverge at bays.
Refraction from the headland causes longshore currents of sediment to be moved into the
bays forming bay beaches.
Tides
Caused by gravitational pull of the moon, sun and earth in orbit.
What causes a high and low tides?
The moon draws water to the side closest to it creating a ‘bulge’, because of gravitational
pull. Note on the opposite side, centrifugal force, causes a high tide.
There is a repel of water on the other sides causing low tides.
What causes the highest high tides and the lowest low tides?
The alignment of the moon and sun (creates strongest force). The sun enhances the moon’s
gravitational pull.
Tides with the greatest range are known as springs.
Neap tides are seven days after springs. Occurs between 2 spring tides. The moon and sun
are at 90 degrees to each other. It is a period of moderately lower tides.
,
