IGCSEGeographyCIERevision Notes2. The Natural Environment2.3 Coasts2.3.1
Coastal Processes
Coastal Processes (CIE IGCSE
Geography)
Coastal Processes
Coastal regions
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Where the land meets the sea is called the coast
The coastline is the edge of the land marked through the high-water mark on
a low-lying coast or the foot of steep sloped coasts
The area between the lowest tide point and the highest point is known as
the shore
Tides are usually twice a day, but vary from coast to coast and with the time
of the year
The difference between low and high tide is known as the tidal range
The tide controls high low and high the waves can work
It is the action of waves and currents that contribute to coastal features
Waves
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Waves are marine processes that erode, transport and deposit material
Waves are formed by winds blowing over the surface of the sea
The size of a wave depends on:
o The speed of the wind
o The fetch (distance the wind travels)
o The amount of time the wind blows (in the same direction)
The greater the strength, time and fetch of the wind, the larger the wave
As a wave approaches the coast and enters shallower water, friction from the
seabed causes the wave to lean forward and eventually will crest and break
onto the beach
The movement of water up the beach is called the swash, and the return
movement is the backwash
There are two types of waves:
o Destructive waves erode the beach. They have a short wavelength,
high-frequency rate and a steep wave gradient. Their backwash is
stronger than their swash, which scours the beach, dragging material
out to sea
o Constructive waves are beach builders. They have a long wavelength,
low-frequency rate and a shallow wave gradient. The swash is stronger
than its backwash, which carries material up onto the beach and
deposits it there
Comparison of Wave Type
Constructive Wave
Destructive Wave
Swash
Strong
Weak
Backwash
Weak
Strong
Wavelength
Long with low height
Short with high height
Frequency
Low (6-8 per minute)
High (10-12 per minute)
Type of beach
Sandy - depositional
Shingle - erosional
Energy
Low
High
Exam Tip
Make sure you are familiar with the way waves are formed and their different
characteristics. Don't be surprised if you are asked to identify the type of wave.
Worked example
Circle the statement below that best describes the characteristics of a
destructive wave?
[1]
long wavelength & weak backwash
short wavelength & weak backwash
short wavelength & strong backwash
long wavelength & strong backwash
Answer
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The answer is a short wavelength & strong backwash [1]:
o A destructive wave has a short wavelength, high frequency rate, steep
wave gradient & a strong backwash
Marine erosion
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Destructive waves are responsible for the majority of erosion that happens
along a coast
They cut into the coastline in four ways:
o Hydraulic Action
o Attrition
o Corrosion
o Abrasion
The effects of attrition are enhanced when the waves move sediment further
and longer
o A large, rough bolder is eventually eroded into round sand grains
(quartz) the longer it stays in the water and the further it travels along
the coast
Rounded pebbles on a beach are known as shingle
Exam Tip
Make sure you know the difference between the four types of erosion, particularly
between abrasion (corrasion) and attrition. So many students confuse these two
terms. A tip for you, is to think of abrasion as rubbing with sandpaper or maybe you
have grazed your knees or elbows when you fell off your bike/skateboard? Those
grazes were abrasions on your knees/elbows etc.
Marine Transportation
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The sea transports sediment that it gets from erosion in the same way as a
river does
Material in the sea arrives from many sources:
o Eroded from cliffs
o Transported by longshore drift along the coastline
o Brought inland from offshore by constructive waves
o Carried to the coastline by a river
Once in the water, the material is moved in different ways:
o Traction
o Saltation
o Suspension
o Solution
Longshore Drift
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It is the main process of transportation along the coast
Influenced by the prevailing wind, waves approach the beach at an angle
As the waves break, the swash carries material up the beach at the same
angle
As the swash dies away, the backwash carries the material down the beach
at right angles (90°)
The process repeats, transporting material along the beach in a zig-zag
movement
Process of longshore drift
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On coasts where longshore drift in one direction, beach sediment is
transported further down the coast
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If obstructed, sediment is prevented from moving and the area further along
the coast is deprived of sediment
This causes two issues:
o Smaller beaches which are less attractive to tourists, causing a loss of
income
o Removes natural coastal protection
Worked example
Describe and explain the process of longshore drift
[4]
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Identify the command words and link to the key term
Command words are 'describe and explain' - say what you see and why
Your focus is on 'longshore drift' - what is it?
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Answer:
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Longshore drift is the process where the waves transport material [1],
such as sand along the beach in the direction of the prevailing
wind [1]. The swash moves material up the beach at an angle [1], as
the waves approach in a similar direction to the wind. The material then
moves back down the beach at 90° due to gravity [1], this is the
backwash. This movement continues along the beach in a zig-zag
motion [1] in the direction of the prevailing wind
Exam Tip
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You can gain full marks using well-annotated diagrams to support your
answer. Just as you like having a visual prompt, it helps the examiner to see
that you do know the answer. Sometimes a diagram is easier than actually
writing it all out.
Longshore drift does not form landforms, it is the process of suppling the
sediment for the process of deposition (which does form features)
Marine Deposition
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The movement of waves carries sand or shingle with them
o Swash carries onto a beach
o Backwash carries it away
When a constructive wave carries sediment up the beach, the largest material
is deposited along the upper reach of the swash
As the backwash moves back down the beach, it loses water and therefore
energy as it travels due to the porosity of the sand
Consequently, the deposition of sediment gets progressively smaller, and the
beach is therefore, sorted by wave deposition, with the smallest mud particles
settling in the low-energy environment offshore
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If a destructive waveform due to a storm, then a large shingle is thrown above
the usual high tide level to form a ridge at the top of the beach called a berm
Sediment Deposition
IGCSEGeographyCIERevision Notes2. The Natural Environment2.3 Coasts2.3.2
Coastal Landforms
Coastal Landforms (CIE IGCSE
Geography)
Erosional Landforms
Cliffs and wave-cut platforms
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Cliffs are steep or sloping rocks, with varying profiles dependent on geology
and topography
The cliff face angle also depends on geology, but also wave attack at its base
- low energy waves are less destructive than high energy ones
Many cliffs have a 'knick-point' around the high-water mark, called the 'wavecut notch', which is where the wave has undercut the rock
Abrasion, corrosion and hydraulic action further extend the notch back into the
cliff
As undercutting continues, the cliff above becomes unsupported and unstable
and eventually collapses
The backwash of the waves, carries away the eroded material, leaving behind
a wave-cut platform
The process repeats and the cliff continues to retreat, leading to a coastal
retreat
The process of cliff retreat and wave-cut platform formation
Headlands and bays
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Found in areas of alternating bands of resistant (hard) and less resistant (soft)
rocks running perpendicular to oncoming waves (discordant coastline)
Initially, less resistant rock (e.g. clay) is eroded back, forming a bay
A bay is an inlet of the sea where the land curves inwards, usually with a
beach.
The more resistant rock (e.g. limestone) is left protruding out to sea as a
headland
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A headland usually features:
o Cliffs along its sides
o Projects out to sea
o Usually longer than it is wide
o Geology is of resistant rock
A bay usually has:
o A wide, open entrance from the sea
o A roughly, semi-circular shape extending into the coastline
o Land that is lower than the headlands surrounding it
o A bay may or may not have a beach
Caves, arches and stacks
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As waves approach the shore, their speed is reduced as they move along the
sea floor
This changes the angle of the waves, and they will turn so the crest becomes
parallel to the coast - known as wave refraction
This refraction concentrates erosive action on all sides of the headland
Any weaknesses in the headland are exploited by erosional processes of
hydraulic action, abrasion and corrosion
As the crack begins to widen, abrasion will begin to wear away at the
forming cave
The cave will become larger and eventually breaks through the headland to
form an arch
The base of the arch continually becomes wider and thinner through erosion
below and weathering from above
Eventually, the roof of the arch collapses, leaving behind an isolated column
of rock called a stack
The stack is undercut at the base by wave action and sub-aerial weathering
above, until it collapses to form a stump
The formation of a cave, arch, stack and stump
Exam Tip
Make sure that you can draw and annotate the formation of this feature as it is a
popular question in the exams.
Remember that attrition is not part of the formation of this feature; attrition is the
knocking together of rocks to smooth and round them.
Corrosion is an active part of the formation of these features, as all salt water is
slightly acidic and most rock contains some soluble minerals that will react with the
salt water.
Sub-aerial weathering (from above) also contributes to the collapse of the arch and
stack.
Depositional Landforms
Beach
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Form in sheltered areas such as bays
Deposition occurs through constructive wave movement, where the swash is
stronger than the backwash
Beach formation usually occurs in the summer months when the weather is
calmer
Sometimes sand from offshore bars can blow onto the shore by strong winds
Blown sand can create sand dunes at the backshore of a beach
Spit
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An extended stretch of sand or shingle that extends out to sea from the shore
Spits occur when there is a change in the shape of the coastline
Or the mouth of a river, which prevents a spit forming across the estuary
A spit may or may not have a 'hooked' end, depending on opposing winds and
currents
A good example is Spurn Point, which stretches for three and half miles
across the Humber Estuary in the northeast of England
Stages of formation:
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Sediment is transported by the action of longshore drift
Where the coastline changes direction, a shallow, sheltered area allows for
deposition of sediment
Due to increased friction, more deposition occurs
Eventually, a spit slowly builds up to sea level and extends in length
If the wind changes direction, then the wave pattern alters and results in a
hooked end
The area behind the spit becomes sheltered
Silts are deposited here to form salt marshes or mud flats
Formation of a Spit
Bar
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When a spit grows across a bay, and joins two headlands together
A bar of sand is formed (sandbar)
Sandbars can also form offshore due to the action of breaking waves from a
beach
Lagoon
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A lagoon is where a small body of water is cut off from the sea
A lagoon may form behind a bar or tombolo
Lagoons do not last forever and may fill with sediment and form new land
Tombolo
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A tombolo is formed when a spit joins the mainland to an island
Chesil Beach in Dorset is a tombolo, as the mainland is joined to the Isle of
Portland
Barrier island
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Barrier islands form parallel to the coast
The main difference between a bar and barrier island is that a bar joins two
headlands, whereas a barrier island is open at one or both ends
Exam Tip
You may be asked to draw and label a diagram showing how depositional landforms
(beaches, spits etc.) are formed. You need to be able to show how sediment is
transported along the coast by waves. Practice drawing and labelling these diagrams
so you can reproduce any of them in the exam. Marks will be awarded for the
accuracy and completeness of your labelling and drawing.
Sand dunes
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Sand dunes are a dynamic environment, with changes occurring quickly
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Sandy beaches are usually backed by sand dunes due to strong onshore
winds which transports dried out, exposed sand
Sand grains are trapped and deposited against an obstacle (rubbish, rocks,
driftwood etc) to form dunes
Dune ridges move inland due to onshore winds pushing the seaward side to
the leeward side
It is the interaction of winds and vegetation that help form sand dunes
Formation of a sand dune
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Windblown sand is deposited against an obstruction - pebble or driftwood
As more sand particles are caught, the dunes grow in size, forming rows at
right angles to the prevailing wind
Over time, the ridges of the dunes will be colonized and fixed by vegetation
in a process called succession
The first plants (pioneer species) have to deal with:
o Salinity
o Lack of moisture as sand drains quickly (highly permeable)
o Wind
o Temporary submergence by wind-blown sand
o Rising sea levels
Coastal Dune Succession
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Embryo dunes
o Wind-blown dried sand is trapped by debris and deposition begins
o Pioneer species such as Lyme Grass and Sea Couch Grass begin to
colonise
o There is little soil content and high pH levels (alkaline)
o Embryo dunes are very fragile and reach a maximum height of 1 metre
Fore dunes
o The embryo dunes bring some protection against the prevailing wind
o This allows other species of plant to grow such as Marram Grass
o Marram grass begins to stabilise the dune with its root system
o These plants add organic matter to the dunes making the dunes more
hospitable for plants that later grow
o A microclimate forms in the dune slack
Maximum height is 5 metres
Yellow dunes
o These are initially yellow but darken as organic material adds humus to
the soil
o Marram grass still dominates the vegetation, but more delicate
flowering plants and insects are found in the dune slacks
o 20% of the dune is exposed, down from 80%
o Height does not exceed 8 metres
Grey dunes
o Grey dunes are more stable, with less than 10% of exposed sand and
have a good range of biodiversity
o Soil acidity and water content increase as more humus is added
o Shrubs and bushes begin to appear
o Height is between 8 - 10 metres
Mature dunes
o As the name suggests, these are the oldest and most stable of the
dunes
o They are found several hundred metres or more from the shoreline
o The soil can support a variety of flora and fauna such as oak trees and
alders (climax vegetation)
o This is the final stage in succession which is known as the climax
community stage
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Worked example
Figs. 3.1, 3.2 and 3.3, show three coastlines.
Identify each of the following landforms:
(i)
landform W in Fig. 3.1
[1]
(ii)
landform X in Fig. 3.2
[1]
(iii)
landform Y in Fig. 3.2
[1]
(iv)
landform Z in Fig. 3.3.
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Answers:
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W - Wave-cut platform
X - Beach
Y - Sand dunes
Z - Cliff
IGCSEGeographyCIERevision Notes2. The Natural Environment2.3 Coasts2.3.3
Coastal Ecosystems
Coastal Ecosystems (CIE
IGCSE Geography)
Coral Reefs
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Coral reefs and atolls are formed through the build-up and compression of the
skeletons of lime secreting, marine animals called polyps
Living coral polyps are found in the upper and outer part of the coral
reef only
Their skeletons are hard, calcareous masses, which form when one
generation dies and the next grows on top, creating an upward and outward
reef
There must be a solid surface to begin the growth of corals, this can be from a
shipwreck or debris from elsewhere
Coral reefs run parallel to the coast, with breaks where river mouths exit
Coral reefs are very sensitive and cannot grow anywhere
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Corals are scattered throughout the tropical and subtropical Western Atlantic
and Indo-Pacific oceans, generally within 30°N and 30°S latitudes
Western Atlantic reefs include these areas: Bermuda, the Bahamas, the
Caribbean Islands, Belize, Florida, and the Gulf of Mexico
The Indo-Pacific Ocean region extends from the Red Sea and the Persian
Gulf through the Indian and Pacific oceans to the western coast of Panama
Corals grow on rocky outcrops in some areas of the Gulf of California
The Great Barrier Reef in northern Australia is renowned for its great
biodiversity and size and can be seen from space
Their distribution is controlled by four factors:
o Temperature
o Light
o Water depth
o Salinity
Features of coral reefs
Global Features
Temperature
Corals cannot tolerate water temperatures below 18°C but grow best at 22°C – 25°C.
Some can stand temperatures as high as 40° C for short periods. This is why coral reefs
normally grow between the Tropic of Capricorn and the Tropic of Cancer -30° of the
equator
Light
Corals need light for photosynthesis due to the algae, called zooxanthellae, that live in
their tissue
Water
Corals are generally found at depths of less than 25m where sunlight can penetrate. The
water must also be clear and clean to allow for optimum photosynthesis to occur
Salinity
Since corals are marine animals, they need salty water to survive, ranging from 32-42%
salt water
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At a local level, other factors will affect development:
o Wave action - corals need well oxygenated, clean water and wave
action provides this
o Exposure to air - although corals need oxygenated water, they cannot
be exposed to air for too long or they will die
o Sediment - all corals need clear, clean water. Any sediment in the
water will block normal feeding patterns by reducing the availability of
light affecting the photosynthesis of the microscopic algae
'zooxanthellae' living in polyp tissue. The corals provide algae with
home and compounds for photosynthesis. In return, the algae produce
food, oxygen and help remove wastes
Types of coral reefs:
Type
Example
Features
These are low, narrow bands of coral, running parallel to the coast and
form around a land mass. They are covered by narrow, shallow lagoons
Coral Coast of
Fringing
at high tide. Their outer edges slope steeply down into the sea beyond.
Fiji
The landward side of the reef has a higher outer edge that rises to the
high tide level.
They range from 500m to several kilometres from the coast and are
Great Barrier, separated by wide deep lagoons below the depth at which the polyps can
Barrier
Australia
live. The Great Barrier Reef has almost 3000 reefs, separated by
channels stretching more than 2300km.
These are narrow, ring-shaped reefs, consisting of a coral rim that
Maldives
encircles a deep lagoon. Sometimes, they may encircle and protect an
Atolls
Suvadiva Atoll island. Channels between islets connect a lagoon to the open ocean or
sea.
Exam Tip
The Great Barrier Reef in the Coral Sea, off the coast of Queensland, Australia is a
good example of a barrier reef.
It is the world's largest coral reef system with over 2,900 individual reefs and 600
islands that stretches for over 2,300 kilometres and can be seen from space.
Salt Marshes
Distribution of salt marshes
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Salt marshes are found all over the world and are not temperature dependant
Like mangroves, they are an ecosystem of the intertidal zone
They are typically very flat, with numerous channels running through them
They form in:
o Coastal areas that are well sheltered, such as inlets and estuaries
where fine sediments can be deposited
o Areas behind spits and artificial sea defences where tidal waters can
flow gently and deposit fine sediments
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They form in brackish water
Features of salt marshes
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Salt marshes are communities of nonwoody, salt-tolerant plants
They begin as tidal mud flats, gaining height as more sediment is deposited
This builds up to and above the level, and frequency of tidal flooding ensuring
that the soil never dries out and remains muddy and sticky
Pioneer species of halophyte plants begin to colonise
As these plants die and add nutrients to the soil, sediment builds up. This
makes the conditions more favourable and other species start to develop.
The process of the development of vegetation, over time is known
as succession. In a salt marsh, this is known as a halophyte
The lower marshes are flooded daily by the rising tide.
They are good coastal defences in some areas, acting as a natural buffer
against coastal erosion and flooding
However, in many areas they have been reclaimed for agriculture or
development, and are threatened by human activities
Mangrove Swamps
Distribution of mangroves
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Both mangroves and coral reefs are found in warm tropical waters, however,
unlike the sensitive coral reefs, mangroves are highly adapted to changing
conditions
This has made them the most successful ecosystems on Earth
Global Distribution of Mangroves
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Originate from south-east Asia and spread across the globe
Mainly found in warm tropical waters and coastal swamps within 30° N and S
of the equator
Some have adapted to more temperate conditions and have colonized as far
south as New Zealand's North Island
They grow in the intertidal zone of the coast
South-East Asia has mangroves with the highest biodiversity in the world
Characteristics of mangroves
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Mangroves are trees that live on the coastline
They sit in water between 0.5 to 2.5 metres high
They range in size from small shrubs to trees over 60m high
They have numerous tangled roots that grow above ground and form
dense thickets
They need high levels of humidity (75 - 80%) and rainfall per annum (1500 3000 mm)
Ideal temperature is around 27° C but are adapting to more temperate
climates
Mangrove root system is complex, with a filtration system to keep salt out
Some have snorkel like roots that stick out of the mud to help them take in air
Others use 'prop' roots or 'buttresses' to keep their trunks upright in the soft
sediment at the tidal edge
Prop Roots
Systems
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Mangrove Root
Snorkel Roots
It is the roots that trap mud, sand and silt which eventually builds up the
intertidal zone into the new land
At the same time, the mangrove is colonizing new intertidal areas
The fruits and seedlings of mangroves can float and can travel many
kilometres on ocean currents
As they drift with the incoming tide, they become lodged in the mud and begin
to grow, colonizing new areas
Worked example
Explain one physical factor that influences the distribution of mangrove
ecosystems
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You would gain 1 mark for identifying a way:
o Temperature, light, water depth, salinity, wind direction, level of shelter
Then 2 marks for development and further explanation
Answer
o Coastal mangroves need a high temperature of around 27° C
otherwise they will not grow, although some mangroves have adapted
to more temperate conditions such as New Zealand
o Mangroves need shallow water between 0.5 to 2.5 metres in depth, but
can survive where the tidal ranges go slightly above or below this level
o Mangroves need high levels of humidity between 75 and 80% to
enable them to grow
o Coastal mangroves need a high level of rainfall between 1500 and
3000 mm per annum, this can be gained from rainfall or moisture in the
air making tropical climates ideal
IGCSEGeographyCIERevision Notes2. The Natural Environment2.3 Coasts2.3.4
Coastal Opportunities & Hazards
Coastal Opportunities &
Hazards (CIE IGCSE
Geography)
Coastal Opportunities
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There are many opportunities that the coast can bring:
Development including:
o Homes
o Shops
o Hotels
o Roads
o Schools
o Restaurants etc.
Nature reserves
Swimming and sports
Industry
Fishing and aquaculture
Tourism
Agriculture
Ports and harbours
Coastal Hazards
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Coastal hazards can be either natural or human induced
Natural hazards include storms, flooding and tsunamis
Human actions cause a variety of issues as shown in the table below:
Opportunities
Consequences
Impacts
Urbanisation and
transport
Dredging and disposal of harbour
sediments; changes in land use ports, harbours and airports; road,
rail and air congestion;
water abstraction; wastewater and
waste disposal
Loss of habitats and species
diversity; visual pollution;
lowering of groundwater table;
saltwater ingress; water
pollution; health
risks; eutrophication;
introduction of invasive species
Industry
Loss of habitats and species
Land use changes; power stations;
diversity; water pollution;
extraction of natural resources;
eutrophication; heat and visual
processing effluents; cooling water;
pollution; decreased input of
windmills; river dams, weirs and
fresh water and sediment to
barriers; tidal barrages
coastal zones; coastal erosion
Agriculture
Land reclamation; fertiliser and
pesticide use; livestock densities;
water abstraction
Fisheries and
aquaculture
Overfishing; impacts on other
species as a result; litter and oil
Ports and harbours; fish processing on beaches; water pollution;
facilities; fishing gear; fish farm
eutrophication; introduction
effluent: shrimp farming
of invasive alien species (IAS);
habitat damage and changes in
marine communities
Loss of habitats and species
diversity water pollution;
eutrophication; river
channelisation; coastal squeeze
Loss of habitats and species
Development and land use changes,
diversity; disturbance of
such as: golf courses; road, rail and
habitats, migration patterns,
air congestion; ports, harbours and
landforms; visual pollution;
Tourism and recreation marinas; water abstraction;
lowering of water table;
wastewater and waste disposal; boat
saltwater ingress in aquifers;
tours and water activities water pollution; eutrophication;
snorkelling, skiing, surfing etc.
human health risks
Exam Tip
Remember that if you are asked to draw on a case study, you MUST name and
locate the place and also use place names to locate specific features.
Natural coastal hazards
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Coastal hazards arise from a number of factors:
o Storm surges - a rapid rise in sea level caused by really low-pressure
storms (e.g. tropical storm)
o Storm tides - occur when there is a combination of high tide and lowpressure storm
o Tsunamis - large sea waves due to underwater earthquakes. The
closer to the coast, the bigger the impact
o King tides
o Sea level rise due to global warming
o High river discharge after a storm - when combined with a spring
tide, water in the estuary cannot discharge into the sea causing a
backflow of water and flooding
Any number of these hazards bring coastal flooding
The biggest impacts are felt by emerging countries, although the biggest costs
are to MEDCs
Tropical storms
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Hurricanes, typhoons and cyclones are all types of tropical storms, the only
difference is where they form:
o Hurricanes form in the tropical North Atlantic Ocean and Northeast
Pacific
o Typhoons form in the Northwest Pacific Ocean
o Cyclones form in the South Pacific and Indian Ocean
In the northern hemisphere they form between May and November
Between October and May in the southern hemisphere
A tropical storm can destroy coastal areas and kill people and the effects are
worse in LEDCs due to lack of economic funds
Other impacts are:
o Destruction of buildings and infrastructure
o Heavy rainfall and storm surges
o Loss of ecosystems, trees, land, crops and animals
o Ships are wrecked at sea and sunk
o Power and communications are lost
o Costs can run into the millions of $ and the effects are greatest in
heavily populated areas
Managing tropical storms is difficult but some of the ways to reduce the risks
are:
o Sea walls and artificial levees to prevent flooding
o Evacuation plans for the population
o Satellite tracking and early warning systems
o Build homes and buildings to withstand strong winds
o Raise homes above storm surge levels and have strong shutters on
windows
o Emergency supplies and shelters
o Have storm insurance
Changing sea levels
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Rising sea levels produce submergent coastlines, with rias and fjords
Falling sea levels produce emergent coastlines, with relic features such as
raised beaches, cliffs with caves, arches etc.
Sea levels have risen and fallen many times in the past
During the last Ice Age, sea levels fell as the water was locked up in glaciers
and ice sheets, rising again as the ice melted
Sea levels are linked to global warming and will have a significant effect on
many low-lying coasts and islands
Many Pacific Ocean islands, such as Kiribati and Tuvalu are at risk of being
completely submerged by rising sea levels
This issue is made worse as many of the world's densely populated areas are
located on coastal lowlands
New York and Miami in the US are major cities vulnerable to sea-level rise as
the cities are built at sea level
Influence of geology
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Geology shapes the coastline over time, place and space
A coastline made up of softer rocks such as sands and clays will be easily
eroded by destructive waves to form low, flat landscapes such as bays and
beaches
Coastlines of more resistant, harder rock will take longer to erode and
produce rugged landscapes such as headlands
The differences between hard and soft rocks will also impact the shape and
characteristics of cliffs
Hard Rock
Shape of cliff
Soft Rock
High and steep
Generally lower and less steep
Cliff face
Bare rock and rugged
Smoother; evidence of slumping
Foot of cliff
Boulders and rocks
Few rocks; some sand and mud
Erosion
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The impact of erosion along the coast is seen globally, however, on local
scale geology has the biggest effect
Areas that are made of less resistant rock such as limestone, sandstone and
boulder clay will erode faster than those coastlines made up of more resistant
rock such as granite
Longshore drift and destructive waves removing sand from beaches exposes
the base of cliffs to higher energy destructive processes
Coastal management can increase rates of erosion further along the coast using groynes to slow down longshore drift depletes sediment elsewhere and
creates shallow beaches which exposes the shore to erosion
Coastal erosion threatens many islands placing residents and tourist resorts
at risk
Tourist and coastal developments all speed up the rate of erosion and remove
natural coastal protection such as mangroves, coral reefs, sand dunes and
salt marshes
Worked example
Study Fig. 2a. Suggest two ways changes in sea level have created coastal
landforms
[4]
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This question tells you to use the figure to show how changes in sea level
have created coastal landforms
You must identify features and then develop your answer to suggest how it
was formed due to changes in sea levels
If you do not refer to the figure, you will not gain full marks
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Possible answer:
o From the figure we can see where the sea level has decreased [1].
This has created an emergent coastline [1] with a relic cliff and raised
beach [1]. Over time, the raised beach has become vegetated,
supporting the observation of changing sea levels [1]
o Wave action [1] from previous sea levels has eroded the relic cliff to
expose a wave-cut notch [1], showing that sea levels used to be higher
than the present [1]. This has led to a relic cliff and sea cave showing
further back than the current cliff face in the figure [1]
IGCSEGeographyCIERevision Notes2. The Natural Environment2.3 Coasts2.3.5
Coastal Management
Coastal Management (CIE
IGCSE Geography)
Managing the Impacts of Coastal Erosion
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There are conflicting views about using a particular type of engineering for
coastal defence
Most coastal managers aim to use a range of methods depending on the
value of what is being protected
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This method is known as Integrated Coastal Zone Management (ICZM)
ICMZ aims to use a combination of methods to best reflect
all stakeholder's needs
Soft engineering methods
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Soft engineering works with natural processes rather than against them
Usually cheaper and do not damage the appearance of the coast
Considered to be a more sustainable approach to coastal protection
However, they are not as effective as hard engineering methods
Soft Engineered Defences
Strategy
Beach
replenishment
Fencing, hedging,
and replacing
vegetation
Description
Pumping or dumping sand
and shingle back onto a
beach to replace eroded
material
Helps to stabilise sand dunes
or beaches
Reduces wind erosion
Advantages
Beaches absorb wave
energy
Widens beach front
Disadvantages
Has be repeated regularly
which is expensive
Can impact sediment
transportation down the
coast
Cheap method to
Hard to protect larger areas
protect against flooding
of coastline cliffs
and erosion
Prevents sudden loss of
large sections of cliff
Cliff re-grading
The angle of a cliff is
reduced to reduce mass
movement
Regrading can also
Does not stop cliff erosion
slow down wave cut
notching at base of
cliffs as wave energy is
slowed
No expensive
Existing coastal defences are
construction costs
abandoned allowing the sea
Managed retreat
to flood inland until it
reaches higher land or a new Creates new habitats
line of defences
such as salt marshes
Disruptive to people where
land and homes are lost
Cost of relocation can be
expensive
Compensation to people and
businesses may not be paid
Hard engineering methods
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Hard engineering involves building some form of sea defence, usually from
concrete, wood or rock
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Structures are expensive to build and need to be maintained
Defences work against the power of the waves
Each type of defence has its strengths and weaknesses
Protecting one area can impact regions further along the coast, which results
in faster erosion and flooding
Hard engineering is used when settlements and expensive installations
(power stations etc) are at risk - the economic benefit is greater than the costs
to build
Hard Engineered Defences
Strategy
Description
Advantages
Disadvantages
Very expensive to build and
maintain
Sea Wall
Groynes
It can be damaged if the
A wall, usually concrete,
Most effective at preventing
material is not maintained in
and curved outwards to
both erosion and flooding
front of the wall
deflect the power of the
(if the wall is high enough)
waves
Restricts access to the beach
Wood, rock or steel
piling built at right
Slows down beach erosion
angles to the shore,
which traps beach
Creates wider beaches
material being moved by
longshore drift
Unsightly to look at
Stops material moving down
the coast where the material
may have been building up
and protecting the base of a
cliff elsewhere
Starves other beaches of
sand. Wood groynes need
maintenance to prevent
wood rot
Makes walking along the
shoreline difficult
Rip-rap
Gabions
Large boulders are piled
up to protect a stretch of
coast
Wire cages filled with
stone, concrete, sand etc
Cheaper method of
construction
Works to absorb wave
energy from the base of
cliffs and sea walls
Boulders can be eroded or
dislodged during heavy
storms
Wire cages can break, and
Cheapest form of coastal
they need to be securely tied
defence
down
Cages absorb wave energy
Not as efficient as other
coastal defences
Can be stacked at the base
of a sea wall or cliffs
Work to break the force of
the waves
Revetments
Off-shore
barriers
Traps beach material behind
them
Sloping wooden or
concrete fence with an
open plank structure Set at the base of cliffs or in
front of the sea wall
Large concrete blocks,
rocks and boulders are
sunk offshore to alter
wave direction and
dissipate wave energy
Cheaper than sea walls but
not as effective
Effective at breaking wave
energy before reaching the
shore
Not effective in stormy
conditions
Can make beach
inaccessible for people
Regular maintenance is
necessary
Visually unattractive
Expensive to build
Beach material is built up
Can be removed in heavy
storms
Low maintenance
Can be unattractive
Maintains natural beach
appearance
Prevents surfing and sailing
Prediction
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Early warning systems allow communities to prepare (evacuate or take
shelter) before flooding occurs
Two methods are used to help forecast coastal flooding:
o Past records (diaries, newspapers, government/council records etc)
▪ These will identify areas that are at high risk of flooding and their
frequency
o Modern technology - GIS, satellite and computer monitoring, weather
stations (local and national) etc
▪ These allow for forecasting and tracking potential hazard events
i.e.
▪ Tropical storms - track the storm's path and associated
storm surge
▪ Earthquakes - size and position if underwater and
possible tsunami outcome
Both these methods of forecasting help officials to say when and where the
event will occur
It indicates the possible strength and scale of the flooding, and the likelihood
of damage and death
Prevention
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Prevention is about taking action that reduces or removes the risk of coastal
flooding
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Actions include:
o Flood defences
▪ These are built along high-risk stretches of coast
o Emergency centres
▪ Centrally placed on higher ground where people can be safe
from flooding
o Early warning systems
▪ Allows for preparation or evacuation of an area
o Education
▪ Informing local people on what to do if and when a flood occurs
o Planning
▪ Planning any new development away from high-risk-areas
▪ Designing buildings to cope with low levels of flooding
▪ Elevating buildings so that flood waters can pass
underneath
▪ Flood proof buildings with raised foundations (fixed or
mechanical)
▪ Reinforced barriers
▪ Dry flood proofing - sealing a property so that floodwater
cannot enter
▪ Wet flood proofing - allows some flooding of the building
o Buffer zones
▪ Areas of land are allowed to flood before reaching settlements
▪ This allows the energy in the surge to dissipate slowing
down the distance the floodwater will travel
▪ It can mean moving people away from the coast which
could be controversial
Coastal strategies
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Management of coastal regions is performed by identifying coastal cells
This breaks a long coastline into manageable sections and helps identify two
related risks:
o The risk of erosion and land retreat
o The risk of flooding
Identification allows resources to be allocated effectively to reduce the
impacts of these risks
The 'cost to benefit' is easier to calculate using coastal cells
Shoreline management plans
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Shoreline Management Plans (SMP) set out an approach to managing a
coastline from flooding and erosional risk
The plans aim to reduce the risk to people, settlements, agricultural land and
natural environments (salt marshes etc.)
There are four approaches available for coastal management, with differing
costs and consequences:
Hold the line
o Long term approach and the most costly
Build and maintain coastal defences so the current position of the
shoreline remains the same
o Hard engineering is the most dominant method used with soft
engineering used to support
Advance the line
o Build new defences to extend the existing shoreline
o Involves land reclamation
o Hard and soft engineering is used
Managed realignment
o Coastline is allowed to move naturally
o Processes are monitored and directed when and where necessary
o Most natural approach to coastal defence
o Mostly soft engineering with some hard engineering to support
Do nothing
o Cheapest method, but most controversial of the options
o The coast is allowed to erode and retreat landward
o No investment is made in protecting the coastline or defending against
flooding, regardless of any previous intervention
Decisions about which approach to apply are complex and depend on:
o Economic value of the resources that would be protected, e.g. land,
homes etc
o Engineering solutions - it might not be possible to 'hold the line' for
moving landforms such as spits, or unstable cliffs
o Cultural and ecological value of land - historic sites and areas of
unusual diversity
o Community pressure - local campaigns to protect the region
o Social value of communities - long-standing, historic communities
o
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Worked example
Explain how gabions protect the coast
[2]
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The command word here is 'explain', therefore, there needs to be
development of the answer for the full marks
Examples include:
o Gabions absorb/dissipates/reduces the wave's energy/power, [1] and
this reduces the impact of the waves at the foot of cliffs and seawalls,
which reduces/prevents coastal erosion [1]
Case Study - Super Typhoon Haiyan
Background
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Typhoon Haiyan (locally called Yolanda) was one of the strongest everrecorded tropical storm to hit the Philippines
It made landfall on the 8th of November 2013 as a Category 5, with sustained
winds of over 195 mph (315 km/hr)
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The Philippines are a series of islands located in the South China Sea, east of
Vietnam and north of Indonesia
The islands regularly suffer from typhoons that sweep in from the southwest
every year during the tropical storm season
The islands sit in an area of usually warm ocean water, however, at time of
storm, the sea temperature was 30°C
Sea level rise (since 1900, has increased 20cm around the world) is a factor
as higher seas are known to contribute to greater storm surges
Abstracting too much groundwater has caused parts of the country to sink
Tacloban stands at the end of a bay that is funnel shaped and this squeezes
water into destructive storm surges
Formation of tropical storms
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All tropical storms need warm, deep water (>27°C and >70 m depth) and
sufficient spin from the earth’s rotation (Coriolis force), hence why they form
between 5-20° N and S of the equator
Warm water encourages evaporation from the sea surface, and as the air
rises, it cools, condenses, releases latent heat and forms large thunderclouds
Heat from below causes further vertical growth and this creates an intense
low pressure
Tropical storms begin with a merging of several storms on the eastern side of
an ocean
A major low-pressure cell develops and as winds are drawn in, the whole
system begins to spin anticlockwise and westwards
Winds rotate around a central eye, where cold air descends creating an
area of calm
The strongest winds are within the wall of the eye.
Typhoon Haiyan's timeline
Path of Typhoon Haiyan November 2013
Date - Nov 2013
Development
2nd
An area of low pressure develops several hundred kilometres east of
Micronesia
3rd
Haiyan begins to track westward, deepening into a tropical depression
5th
6th
7th
8th
10th
11th
Classified as a typhoon and a low-level Public Storm Warning is issued by
Philippines Atmospheric, Geophysical and Astronomical Services
Administration (PAGASA)
Declared a Category 5 super typhoon by the Joint Typhoon Warning Center.
PAGASA raises storm warning to highest level, indicating expected wind
speeds in excess of 115 mph
Haiyan's winds continue to intensify up to 195 mph. Haiyan makes first landfall
at Guiuan, Eastern Samar without losing any intensity
Haiyan makes five more landfalls within the Philippines before passing into the
South China Seas
Haiyan turns to the NW and makes landfall in Northern Vietnam, as a Category
1 typhoon
Haiyan finally weakens into a tropical depression
Typhoon Haiyan's characteristics
Lowest pressure
895 mb
Peak strength
Category 5
Strength at landfall
Category 5 with 195 mph winds
Highest sustained wind speed
196 mph
Radius of typhoon strength winds
53 miles
Rainfall
400 mm
Storm surge height
15 m
Preparation for Typhoon Haiyan
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The Philippines, despite being an LEDC, take disaster preparations seriously
as they have experience of typhoon impacts, as they are usually the first
Pacific landmass in a typhoon's track
The Philippines have been practicing risk reduction and resilience for decades
and have published risk maps and provided evacuation shelters
When Haiyan made first landfall, the International Charter on Space and
Major Disasters was activated, this allowed relief agencies, in times of
disasters, to have access to satellite data from space agencies to help in relief
and recovery
The military deployed planes and helicopters in advance to areas expected to
be worst hit
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Community buildings, such as convention centres, were designated as storm
shelters, but there were concerns that they would not withstand the wind
As a result of years of community preparedness and education, there were
evacuations of whole islands, such as Tulang Diyot, with all 1000 residents
leaving ahead of Haiyan
The local mayor won an award in 2011 for community work based on the
“Purok system”, which is where community members agree to deposit their
own money into a community fund, on a regular basis, for post-disaster
assistance, rather than waiting for government aid
Impacts of Haiyan
Total economic loss
$13 billion
Homes damaged or destroyed
1.1 million
Displaced people
4 million
Number of deaths
6201
Number of people missing
1785
Number of injured people
28,626
Number of people affected
16 million
Impacts
Short-term
Long-term
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Social
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Economic
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6201 people died
1.1 million homes lost
more than 4 million displaced
Casualties 28,626 from lack of
aid
16 million people affected
UN admitted its response was too
slow, amid reports of
hunger/thirst among survivors
Estimated at $13 billion
Major sugar/rice producing areas
were destroyed
Between 50,000 and 120,000
tons of sugar was lost
Over 130,000 tonnes of rice were
lost
Government estimated that
175,000 acres of farmland was
damaged (worth $85 million)
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UN feared possibility of the
spread of disease, lack of food,
water, shelter and medication
Areas less affected; influx of
refugees into the area
Two months later, 21,000
families were still in 380
evacuation centres, waiting to be
rehoused by the government in
bunkhouses that needed to be
built
The Philippines declared 'a state
of national calamity’
Asked for international help the
next day
President Aquino was under
growing pressure to speed up the
distribution of
food/water/medicine
Tacloban city was decimated
Debt is a major obstacle for the
Philippines, the country is locked
in a debt cycle, with more than
20% of government revenue
spent on foreign debt repayments
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Environmental
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Loss of forests/trees, and
widespread flooding
Oil and sewage leaks; into local
ecosystems
Lack of sanitation in days
following lead to a higher level
of pollution
Coconut plantations were said to
be 'completely flattened' (coconut
equated to nearly half of the
Philippines agricultural exports /
is the world's biggest producer of
coconut oil
Fishing communities were
severely affected
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An estimated 90 per cent of the
rural population in typhoonaffected areas are small-scale
farmers
With 33 million coconut trees
felled, international help has been
sought to mill the 15 million tons
of timber,
lying rotting on the ground,
attracting pests that threatened
healthy trees
Without a crop, families would
not have cash to enable local
markets to function
Immediate relief
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The immediate response was from the survivors, who searched flattened
buildings for bodies
The government was criticised for being slow in its response, and people
began looting to find food supplies
Roads were undamaged, but debris slowed rescue vehicles
Airports and harbours were closed meaning emergency teams had to travel
slowly on foot, which hampered aid distribution
International charities sent emergency supplies, centred on Tacloban airport
with the UK and USA sending diggers, land rovers and heavy lifting gear
The European Commission released $4m in emergency funds and the UK
Rapid Response Facility provided $8m in aid
Twelve IFRC (International Federation of the Red Cross) Emergency
Response Units worldwide were deployed
The Philippines was also dealing with two prior natural disasters - 7.3
magnitude earthquake a month earlier (October 2013) and Typhoon Bopha in
2012. Together these disasters meant that the Philippines were low on
resources - financial, material and human