3E 4E Coasts

CoastsCoasts
Coast and Factors Affecting Coastal
Environments

Guiding QuestionsGuiding Questions
1. Where is the coast?
2. Why are coastal environments dynamic?

By the end of the lesson…By the end of the lesson…
We will be able to,
1.Define the coast.
2.Explain the factors affecting coastal
environments.

Where is the coast?Where is the coast?

Where is the coast?Where is the coast?
• The area where the land meets the sea.
• Covers the area of land that is affected by
waves and tides.

Factors Affecting CoastalFactors Affecting Coastal
EnvironmentsEnvironments
1. Waves
2. Tides and sea level changes
3. Currents
4. Geology
5. Types of ecosystems
6. Human activities

WavesWaves
• A wave is a long body of water that curls into
an arched form which breaks onto the coast.
• Waves are formed when kinetic energy from
wind blowing across surface of seas and
oceans is transferred to the water.
• Waves affect coastal environments by serving
as the main agent for the coastal processes of
erosion, transportation and deposition.

Tides and Sea Level ChangesTides and Sea Level Changes
• Tides refer to the daily alternate rise and fall in
the sea level caused mainly by effects of
gravitational pull of the moon and sun.
• Tides affect coastal environments as they
determines the activity of coastal processes. For
example, erosion and transportation processes
are more dominant during high tides then low
tides.
• Changes in sea levels may release massive
volumes of water into seas and oceans, thereby
creating new coastlines.

CurrentsCurrents
• Ocean currents are large-scale, continuous
movement of water in seas and oceans driven
largely by prevailing wind which generally
blow in one direction.
• Ocean currents affect coastal environments
as they carry massive amounts of energy,
which influences the extent and intensity of
coastal processes.

GeologyGeology
• Geology refers to the arrangement and
composition of rock.
• Geology affects coastal environments as
more resistant rocks such as granite and
basalt erodes slower than less resistant rocks
such as limestone and shale.
• Rocks with more cracks and joints are more
vulnerable to erosion.

Types of EcosystemsTypes of Ecosystems
• The type of ecosystem influences coastal
environments through their interactions
with coastal processes.
• For example, coastal ecosystems serve as
natural barriers that slow down the speed
and impact of waves on coasts.
• Mangroves ecosystems, in addition to serving
as natural barriers, traps sediments hence
reduce coastal erosion.

Human ActivitiesHuman Activities
• Human activities influence coastal
environments through activities such as
shipping, recreational activities and building
and operating marine structures.
• These activities can result in significant
changes to the coast over short periods of
time.

1. What influences wave energy?

We will be able to,
1.Describe the factors influencing wave energy.
2.Describe the different types of waves and
their associated landforms.

Wave TerminologyWave Terminology

Factors InfluencingFactors Influencing
Wave EnergyWave Energy
1. Wind speed
2. Duration of wind
3. Fetch

1. Wind Speed1. Wind Speed
• The faster the wind blows, the greater the
wave energy is.

2. Duration of Wind2. Duration of Wind
• The longer the wind blows, the larger the
waves are and the greater the wave energy.

3. Fetch3. Fetch
• Refers to the
distance travelled by
winds over open
seas.
• The greater the
fetch, the more
energy the waves
have.

Waves close to the coastlineWaves close to the coastline

Wave MovementsWave Movements
• All waves have two movements.
– Swash
• Forward movement of waves.
• Transports sediments up the shore.
– Backwash
• Waves that flow back to the sea due to gravity.
• Transports sediments back to the sea.

Types of wavesTypes of waves
• Constructive waves
• Destructive waves

Waves and LandformsWaves and Landforms
• Constructive waves form depositional
landforms.
– Bay
– Beach
– Spit
– Tombolo

Waves and LandformsWaves and Landforms
• Destructive waves form erosional landforms.
– Headland
– Cliff
– Shore platform/Wavecut platform
– Cave
– Arch
– Stack

QuizQuiz
• Compare the difference between
constructive waves and destructive waves.
[3]

We will be able to,
1.Explain the process of wave refraction.

Wave RefractionWave Refraction
• Refers to the process whereby wave speed
and direction changes as waves encounter
different depth of water.

• Wave speed is reduced and wave direction
changes as waves encounter friction from the
seabed.
• Waves experience more friction from the
steeper seabed in front of headlands and
converges.
• This increased wave height and wave
frequency which lead to more erosion at the
headland.

• Waves experience less friction from the
gentler seabed when it enters the bay than
the headlands and diverges.
• This decreased wave height and wave
frequency which lead to less erosion at the
bay area.

1. Waves converge at
the headland.
2. Waves diverge at
the bay.

CoastsCoasts
Coastal Processes

1. What are coastal processes?

We will be able to,
1.Describe coastal processes.

Coastal ProcessesCoastal Processes
1. Erosion
2. Transportation
3. Deposition

Coastal ErosionCoastal Erosion
• Hydraulic action
• Abrasion or Corrasion
• Attrition
• Solution or Corrosion

HHydraulic Actionydraulic Action
• Waves striking against
a rock surface trap air
in its joints.
• This air is compressed
by the oncoming
waves, exerting
pressure on the joints.
• Over time, these joints
weaken and the rocks
shatter.

Abrasion orAbrasion or CCorrasionorrasion
• As waves break, sediments carried by waves
such as sand and rocks are hurled against the
coast.
• These loosened sediments knock and scrape
against the coastal cliffs. This weakens the
surface, resulting in the breaking down of the
coast.
• Over time, the impact from abrasion is
powerful enough to undercut a cliff.

AAttritionttrition
• When rock particles carried by waves rub or
hit against one another, they break down
into smaller pieces and become smoother
and more rounded over time.

SSolutionolution
• Sea water reacts chemically with water-
soluble minerals in coastal rocks and
dissolves them.
• For example, limestone rocks are easily
eroded by carbonic acid in solution.
• When solution of minerals occurs, rocks are
weakened and will eventually disintegrate.

QuizQuiz
• Describe how coasts are eroded. [2]
• Coasts are eroded in the following ways
namely hydraulic action, attrition, abrasion
and solution.
• Hydraulic action refers to…
• Attrition refers to…

Coastal TransportationCoastal Transportation
• Waves approach the coast diagonally/at an
oblique angle and create longshore currents,
which are currents that flow parallel to the
coast.

• Swash carries material up the beach
diagonally/at the same oblique angle.
• while backwash carries material down the
beach perpendicularly/at right angle due to
the pull of gravity.
• This results in a zig-zag movement of
materials along the beach known as beach
drift.

• Both longshore currents and beach drift
transport sediments along the coast.
• The combined effect of sediment movement
by longshore currents and beach drift is
known as longshore drift.

Coastal DepositionCoastal Deposition
• Waves deposit when wave energy decreases
such that waves are unable to carry
sediments.
• Larger sediments are deposited first followed
by smaller sediments.

Coastal DepositionCoastal Deposition
• Deposition is more dominant along sheltered
coasts where destructive waves are less
common.

QuizQuiz
• With the use of a well-labeled diagram,
explain how transportation takes place along
the coast. [6]

CoastsCoasts
Coastal Landforms

We will be able to,
1.Explain the formation of cliffs and shore
platforms/wavecut platforms.

Cliffs & Shore PlatformsCliffs & Shore Platforms
• Hydraulic action and
abrasion attack lines of
weakness on the rock
surface forming a notch
overtime.
• As erosion continues, the
notch deepens and develops
into a seacave, which is an
underground chamber with
an overhanging roof.

Cliffs & Shore PlatformsCliffs & Shore Platforms
• Overtime, the overhanging roof
collapses due to the force of
gravity, forming a steep rock face
known as a cliff.
• The materials from the collapsed
roof are carried by waves and
thrown against the base of the
cliff, causing further erosion.
• As this process repeats overtime,
the cliff will retreat inland,
leaving a gently-sloping platform
known as a shore platform.

We will be able to,
1.Explain the formation of headlands and bays.
2.Explain the formation of caves, arches and
stacks.

Headlands and BaysHeadlands and Bays
• Formed when
alternate bands of
more resistant and
less resistant rocks
are arranged at right
angles to the coast.

Headlands and BaysHeadlands and Bays
• The less resistant rocks
erodes faster than the
more resistant rocks,
forming wide indented
coasts, known as bays.
• The remaining more
resistant rocks extend
into the sea and are
known as headlands.

CavesCaves
• Waves attack lines of
weakness and
undercut the base of
headlands.
• Continuous action of
waves hollowed out
the headland,
forming a cave.

ArchesArches
• As wave action
continues, adjacent
caves are eventually
eroded through and
joins, leaving a
bridge of rock
known as an arch.

StacksStacks
• After a period of
time, the roof of the
arch collapses due to
the force of gravity
to form a pillar of
rock in the sea,
known as a stack.

We will be able to,
1.Explain the formation of spits and tombolos.

SpitSpit
• As the direction of the
coastline changes abruptly,
longshore drift continues
to transport materials in
the original direction for
some distance.
• This results in the
deposition of transported
beach materials into the
sea, which accumulate over
time.

SpitSpit
• As the materials continue to
accumulate, they eventually
appear above the surface as a
long narrow ridge of sand or
pebbles with one end
attached to the land, which is
known as a spit.
• Wave refraction acting on the
end of the spit eventually
causes it to curve, forming a
hooked spit.

TomboloTombolo
• If an offshore island lies near the mainland where
the spit is forming, the spit may continue to extend
until it connects the offshore island to the mainland,
forming a tombolo.

QuizQuiz
• With the aid of well-labelled diagrams,
explain how a cliff is formed. [7]

CoastsCoasts
Coastal ecosystems

Guiding QuestionGuiding Question
1. What are the ecosystem services that people
can obtain from the coastal ecosystem?

We will be able to,
1.Describe the four key ecosystem services
obtainable from coastal ecosystem.

Ecosystem ServicesEcosystem Services
1. Provisioning services
2. Regulating services
3. Cultural services
4. Supporting services

Ecosystem ServicesEcosystem Services
1. What does the coast provide?
2. What does the coast regulate?
3. What culture does the coast inculcate?
4. What does the coast support?

1. Provisioning Services1. Provisioning Services
a. Fish and other types of seafood
b. Water
c. Building and ornamental materials

a. The coast provides fish and other types of
seafood which serves as the main dietary
protein for more than 1 billion people and
provides employment and income for over
100 million.

b. The coast also provides water as seawater
can be desalinated to become drinking
water. For example, Singapore practices
desalination to ensure the sustainability of
fresh water.

c. In addition, the coast is a source of building
and ornamental materials. For example,
mangroves is a source of wood that can be
used for building boats, houses and
converted into charcoal. Corals can also be
crushed and made into cement or made into
ornaments for sale as souvenirs.

2. Regulating Services2. Regulating Services
a. Shoreline stabilization
b. Flood prevention
c. Storm and natural hazard protection

a. The coast helps to stabilize the shoreline
as coral reefs and mangroves cause waves to
break and lose their energy, thereby
reducing the impact of shoreline erosion
hence protecting existing shoreline.

b. The coast helps to prevent floods as sandy
beaches are able to disperse water and sand
dunes act as natural barriers to advancing
waters, thereby reducing the risk of
flooding.

c. The coast provides protection against
storms and natural hazards. For example
mangroves and corals offers protection
against heavy storms and tsunamis as wave
energy is absorbed or reduced hence
reducing the full impact of destructive
waves on the coast.

3. Cultural Services3. Cultural Services
a. Recreational benefits
b. Aesthetic benefits
c. Spiritual benefits

a. The coast provides recreational benefits
as they are popular venues for leisure
activities such as swimming and sailing. For
example, Gold Coast, Australia, with its 60
kilometres of beach, attracts around 1o
million visitors every year.

b. The coast also provides aesthetic benefits
as they are scenic places which draw visitors
who enjoy the quietness of the sea and
people who appreciate nature.

c. Coasts are spiritual places especially for
coastal communities that depend on the
seas for their livelihood. For example, it is
common to find temples dedicated to sea
deities along the coasts of Taiwan and Bali,
Indonesia.

4. Supporting Services4. Supporting Services
a. Mangrove habitat
b. Beach habitat

a. The coast supports mangroves habitats as
the area between the roots, mud and water
of mangroves provide living creatures with
food, protection from predators and
grounds for breeding.

b. The coast supports beach habitats which
play key roles in the life cycles of various sea
creatures. For example, fish fry swims in the
shallow waters and gain size before
venturing into deeper waters and sea turtles
lay their eggs in the beach sand.

CoastsCoasts
People and Coastal Areas

By the end of the lessonBy the end of the lesson
We will be able to
1.Describe how the coast is useful to people.

1. How do people use coastal areas?

Uses of Coastal AreasUses of Coastal Areas
1. Fisheries and aquaculture
2. Housing and transportation
3. Tourism and recreation
4. Ports, harbours and piers
5. Wind farming
6. Desalination
7. Sand mining, salt extraction
8. Oil refining

• Fisheries and aquaculture activities are
found along coast which refers to the farming
of fish in fisheries or fish farms to meet the
growing demand of fish.
• For example, the province of Ca Mau in
Vietnam is the nation’s shrimp production
centre and generates US$800 million in
revenue in 2010.

• Coastal areas are spaces for housing and
transportation and many people make use of
boats as transport to facilitate economic
activities like fishing and tourism.
• For example, the people living in stilt houses
and floating fish farms in the coastal town of
Kukup, Malaysia, uses boat ferry services to
carry out their daily activities.

• Coastal areas are popular spaces for tourism
and recreation activities and make up the
most important component of international
tourism.
• For example, the pristine beaches of Sentosa,
Singapore is a popular tourism honeypot that
drew millions of tourists every year.

• Coastal areas are home to ports, harbours
and piers which are gateways to foreign
trade.
• For example, the Port of Shanghai, connected
by the Yangtze River, serves the vast
economically-developed areas of Anhui,
Jiangsu and Zhejiang and moved 650 million
tons of goods in 2010 to become the world’s
busiest port.

• Higher wind speeds are available offshore
compared to on land, hence wind farming
operations can be conducted along coastal
areas.
• For example, the Greater Gabbard Wind
Farm off the coast of Suffolk in England is the
largest offshore wind farm in the world and
estimated to generate 1.75TWh per year.

Greater Gabbard Wind Farm, England

• Sea water can be desalinated to produce fish
water by removing salt and other minerals
from the saline water to produce fresh water
suitable for human consumption or irrigation.
• For example Australia, being the driest
continent has invested heavily on desalination
plants to boost drinking water supplies that
traditionally depended on rainfall collected
from behind dams.

• Coastal areas are sources of sand that can be
mined or extracted for nourishing erosional
beaches or for construction.
• For example, about 219,000 cubic metres of
sand is mined yearly from Kaipara Harbour,
New Zealand to produce concrete for
construction and asphalt for surfacing roads.

• Oil refining refers to the processing of crude
oil into refined products such as petroleum,
diesel and gasoline and are commonly found
along coastal areas for easy access to ports.
• For example, large oil refining plants are
located on the offshore island of Jurong
Island, Singapore with the capacity to refine
over a million barrels of crude oil per day.

CoastsCoasts
Coral Reef Ecosystems

1. Why are costal reef ecosystems distinctive
and valuable?
2. What pressures are coral reefs facing?

We will be able to
1.Describe the global distribution of coral reef
ecosystems.
2.Describe the favorable conditions for growth.
3.Explain the value of coral reef ecosystems in
the coastal environment.
4.Describe the pressures on coral reef
ecosystems.

DistributionDistribution
• Mostly found between the Tropic of Cancer
and the Tropic of Capricorn.
• Highest concentration in Southeast Asia.

Conditions for GrowthConditions for Growth

Conditions for GrowthConditions for Growth
• Suitably strong wave action that brings food and
oxygen supplies.
• Low levels of sedimentation to prevents
suffocating living corals.
• Sea surface temperature not lower than 17°C.
• Average salinity.
• Clear water between 10 – 60m to allow sunlight
to penetrate for algae to photosynthesis.
• Low turbidity.

Value of Coral ReefsValue of Coral Reefs
1. Supports natural ecosystems
2. Absorbs wave energy
3. Serves as tourist attractions
4. Source of materials for jewelry and
ornaments

1. Coral reef supports natural ecosystems by
sustaining a wide range of marine creatures
to breed and grow which include more than
25% of marine fish species.

2. Coral reefs protect the coast against the full
force of waves by serving as natural
protective barriers that absorb wave
energy generated in the open seas.

3. Coral reefs are tourist attractions that
attract divers and beach goers whose
activities provide jobs and income for
tourist industry.

4. Corals is a source of materials for making
jewelry and ornaments which can then be
sold as souvenirs to tourists, thereby
generating jobs and income for the local
communities.

Pressures on Coral ReefsPressures on Coral Reefs
1. Overfishing
2. Irresponsible fishing methods
3. Recreational use of coast
4. Pollution
5. Siltation
6. Costal development
7. Climate change

TaskTask
• Describe two pressures faced by coral reefs.
[2]

CoastsCoasts
Mangroves Ecosystems

1. Why are mangroves ecosystems distinctive
and valuable?
2. What are the pressures on mangroves?

We will be able to
1.Describe the global distribution of mangroves.
2.Describe the value of the mangrove
ecosystem in the coastal environment.
3.Describe the pressures on mangrove
ecosystems.

DistributionDistribution
• Along coasts of countries between the Tropic
of Cancer and Tropic of Capricorn.
• For example, in countries of Southeast Asia,
Venezuela and Brazil in South America and
Senegal and Sierra Leone in Africa.
• Patches of mangroves north of the Tropic of
Cancer along the coasts of Mexico and south
of the Tropic of Capricorn along the coasts of
Australia.

Zonation of MangrovesZonation of Mangroves

Adapting to theAdapting to the
Coastal environmentCoastal environment
• Trees such as the
Avicennia have
pencil-liked aerial
roots that enable
them to take in
oxygen in
waterlogged
conditions.

Rhizophora have
prop roots that
enable them to
anchor to the soft,
muddy ground for
stability against
waves.

Bruguiera have
kneed roots that
enable them breathe
and also serves as
anchor to the soft,
muddy ground.

• Some trees such as the
Rhizophora bear fruits
that are javelin-shaped so
they can pierce the soft
mud to germinate and
grow into a sapling
immediately without
being washed away by
the waves.

• Mangrove trees are
salt tolerant and some
have developed ways
to secrete salt.
• For example the
Avicennia leaves have
special glands that
secrete the salt taken
in from the saline
water.

• Most mangrove trees produce fruits that are
buoyant, allowing them to float away and
germinate in other coastal areas.

Value of MangrovesValue of Mangroves
1. Stabilizing shorelines
2. Breeding ground and habitat
3. Wood for fuel
4. Improves water quality

1. Mangroves are valuable as they stabilize
shorelines with their dense roots system which
absorbs energy of waves and slows down the water
thereby reducing coastal erosion. In addition,
sediments washed down by rivers and washed up
by waves are collected and deposited amongst the
mangrove roots. For example, some 5 million
mangrove trees were planted along the coastal
areas of Malaysia since 2005 as protection against
the devastating impact of tsunamis and to manage
the loss of sediments.

2. Mangrove ecosystems are valuable
breeding grounds and habitats for
marine life. For example, barnacles, oysters
and sponges anchor on the hard surfaces of
aerial roots and shrimps, crabs and lobsters
forage for food in the middy sediments
between the mangrove roots.

3. Mangrove forests is a source of wood for
fuel, construction, charcoal and feed for
livestock. For example, communities living
near mangroves have been known to make
charcoal from wood collected from
mangrove trees and feed leaves from
mangrove trees to their sheep and goats.

4. Mangrove trees improve water quality as
their dense network of roots is able to trap
waste materials and fine sediments hence
acting as natural filters for purifying water.

Pressures on mangrovesPressures on mangroves
1. Demand for fuel wood and charcoal
2. Need for more farming areas
3. Land reclamation
4. Water pollution
5. Rising sea level

CoastsCoasts
Threats to coastal areas

• What are the threats to coastal areas?

We will be able to
1.Identify and explain the threats to coastal
areas.

Threats to Coastal AreasThreats to Coastal Areas
1. Climate change
2. Eroding shorelines
3. Rising populations
4. Coastal development and habitat loss
5. Pollution

1. Climate change have led to global
warming, which have resulted in rising sea
levels that could submerge low-lying coasts
and landforms such as sandy beaches and
deltas.

2. Shorelines are eroding more rapidly as
global warming has resulted in more severe
storms capable of altering shorelines over a
short period time and destroy corals.

3. Close to half of the world’s population live
within 100 km of the coast and as the
world’s population increases, more
coastal sites will be developed and more
coastal resources will be exploited, leading
to coastal degradation.

4. Habitats are destroyed when coasts are
altered with human structures such as ports
and resorts.

5. Pollution is largely caused by the disposing
of waste into the sea that could destroy the
coast and endanger marine life. For
example, the Great Pacific Garbage Patch is
a mass of garbage that has accumulated in
the Pacific Ocean over time.

CoastsCoasts
Sustainable Management of Coastal
Areas

1. How can coastal areas be managed?

We will be able to
1.Evaluate the effectiveness of strategies to
achieve sustainable management of coastal
areas.

Sustainable ManagementSustainable Management
of Coastal Areasof Coastal Areas
1. Limit damaging activities
2. Protect coastal resources
3. Restrict development

Sample QuestionSample Question
1. Evaluate the effectiveness of strategies to
achieve sustainable management of coastal
areas. [8]
– Point (Describe your point)
– Explain (Explain the significance of your point)
– Examples [Explain how your point is effective
with the use of named example(s)]
– Limitations [Explain how your point is
ineffective with the use of named example(s)]

Limit damaging activitiesLimit damaging activities
• Point:
– Damaging activities such as blasting coral reefs
and clearing mangroves can be controlled to
reduce the damage to coastal areas.
• Explain:
– National and local government bodies can work
together to carefully manage the needs and
demands of the people together with the nature
of the coastal environment.

• Example:
– For example, sand dunes stabilized by
vegetation along Port Philip Bay in southern
Victoria, Australia were often trampled on by
beachgoers leading to the destruction of the
dune vegetation. As a result, the houses
behind the sand dunes were buried by large
volumes of sand. This led the authorities to
fence off the dunes hence allowing the coastal
environment to recover.

• Limitation:
– However, it is difficult to strike a balance
between the needs of the environment and
people as in the case Australia, residents and
visitors to Port Philip Bay complained that the
fences are unsightly and created
inconveniences for them when navigating the
beach.

Protect Coastal ResourcesProtect Coastal Resources
• Point:
– Protecting coastal resources refers to efforts
undertaken to prevent resources from being
exploited or depleted.
• Explain:
– Resources such as fish, corals and mangroves
can be protected so as to allow the
environment to rest and recover.

• Example:
– For example, in Goat Island Marine Reserve,
New Zealand, specific areas known as marine
reserves are created to protect marine
ecosystems and allow fish and marine
creatures to breed and thrive. Due to the
effort of the reserve, there is now significantly
more fish in the reserve than outside it,
demonstrating the success of this strategy.

• Limitation:
– However, protecting coastal reserves are not
without problems as local communities who
have been depending on the coastal resources
for a living are denied from accessing
resources that have supported them for a long
time.

Restrict developmentRestrict development
• Point:
– Restricting development in coastal areas
especially prone to natural hazards refers to the
implementation of management policies to deal
with the threat of natural hazards.
• Explain:
– Despite the occurrence and unpredictability of
natural hazards, coastal areas still draw visitors
and investors who often have to spend large
amounts of resources to repair and rebuild after a
natural hazard .

Restrict developmentRestrict development
• Example:
– For example, the Federal Emergency
Management Agency of the USA ensures that
structures are built away from areas prone to
natural hazards.
• Limitation:
– However, this strategy can only be effective
with strong enforcement and are normally
less effective in less developed countries such
as Indonesia due to rampant corruption.

CoastsCoasts
Coastal Protection Measures

1. What are the coastal protection measures?

We will be able to
1.Evaluate the effectiveness of coastal
protection measures.

Coastal Protection MeasuresCoastal Protection Measures
• Soft engineering
– Protecting the coast using natural processes
and does not involve the construction of any
physical structures.

• Soft engineering
1. Beach nourishment
2. Planting vegetation
3. Stabilizing sand dunes
4. Encouraging growth of coral reef

• Hard engineering
– The construction of physical structures to
protect coasts against the erosive power of
waves.

• Hard engineering
1. Seawalls
2. Gabions
3. Breakwaters
4. Groynes
5. Tetrapods

Sample QuestionSample Question
1. Assess the effectiveness of coastal protection
measures. [8]
– Point (Describe your point)
– Explain (Explain the significance of your
point)
– Examples [Explain how your point is
effective with the use of named example(s)]
– Limitations [Explain how your point is
ineffective with the use of named example(s)]

SeawallsSeawalls
• Point:
– Seawalls are solid walls made of resistant
materials such as concrete, rocks, or wood
built parallel and on the coast.
• Explain:
– They are effective in managing coastal erosion
as they absorb and deflect wave energy from
attacking the coast.

SeawallsSeawalls
• Example:
– For example, seawalls built along the Esplanade,
Singapore has been effective in preventing
erosion from affecting human properties and
structures along the coast.
• Limitation:
– However, seawalls are costly to maintain as the
backwash of deflected waves washes away the
beach materials at the base of seawalls,
undermining their stabilitym which will
eventually lead to their collapse.

GabionsGabions
• Point:
– Gabions are wire cages filled with small rocks
piled up and placed along the coast.
• Explain:
– Gabions are effective in preventing coastal
erosion as the gaps between the rocks allow
water to filter through hence weakening wave
energy.

GabionsGabions
• Example:
– For example, gabions placed along Hornsea
Beach, England have been effective in
reducing the impact of coastal erosion.
• Limitation:
– However, they offer only short-term
protection as the rocks are easily eroded away
by waves and the cages corrode easily and are
unsightly.

BreakwatersBreakwaters
• Point:
– Breakwaters are solid walls usually made of
granite built off and parallel to the coast, or
with one end attached to the coast.
• Explain:
– Breakwaters are useful as when constructed
offshore, a zone of calm water is created
behind them, which encourages deposition to
form beaches.

BreakwatersBreakwaters
• Example:
– Breakwaters have been installed along East Coast
Park, Singapore and have been successful in
mitigating the effects of coastal erosion.
• Limitation:
– However, breakwaters protect the coast unevenly
as only the zones behind the breakwaters are
protected while exposed sections are still
vulnerable to erosion.

GroynesGroynes
• Point:
– Groynes are solid low walls usually made of
granite or wood built on and perpendicular to
the coast.
• Explain:
– They are useful as they disrupt the direction
of longshore drift thereby encouraging
deposition on the updrift side of the groyne
that faces longshore drift.

GroynesGroynes
• Example:
– For example, groynes built along St Leonard
Beach, Canada have successfully mitigated
the effects of longshore drift.
• Limitation:
– However, no fresh materials are deposited on
the downdrift side of the groyne, which leads
to an uneven and unsightly coastline.

TetrapodsTetrapods
• Point:
– Tetrapods are four-pronged concrete
structures stacked offshore in interlocking
positions.
• Explain:
– Tetrapods are able to dissipate wave energy as
they allow waves to pass around them rather
than hit against them, reducing the possibility
of them being damaged by waves.

TetrapodsTetrapods
• Example:
– Tetrapods have been used by Crescent City,
northern California, for many years as defense
against the impact of tsunamis, which occurred 31
times between 1933 and 2008.
• Limitation:
– However, tetrapods are aesthetically unappealing
and also pose a danger to swimmers, surfers and
boaters.

Beach NourishmentBeach Nourishment
• Point:
– Beach nourishment refers to the
replenishment of large quantities of sand to
the beach.
• Explain:
– This is useful as it extends and improves the
beach and protects the beach against storms.

Beach NourishmentBeach Nourishment
• Example:
– Beach nourishments applied along East Coast
Park, Singapore has been successful in
mitigating the effects of coastal erosion.
• Limitation:
– However, beach nourishment is expensive
and the eroded sand that washes out to seas
may destroy marine life.

Planting VegetationPlanting Vegetation
• Point:
– Vegetation such as mangrove trees can be
planted along the coast to manage the
coastline.
• Explain:
– This is effective as prop roots of mangroves
are able to secure and trap sediments and
extend the coastal land seawards.

Planting VegetationPlanting Vegetation
• Example:
- For example, mangrove trees planted along the
west coast of Peninsular Malaysia has been
effective in preventing coastal erosion.
• Limitation:
- However, not all coastal regions can support
mangroves and planting mangroves can cause the
shore to become shallower hence affecting port
activities.

Stabilising Sand DunesStabilising Sand Dunes
• Point:
– Sand dunes can be strengthened by planting
vegetation such as small trees and shrubs.
• Explain:
– This is effective as sand dunes act as natural
barriers to coastal erosion and by anchoring
the sand, coastal erosion can be managed.

Stabilising Sand DunesStabilising Sand Dunes
• Example:
– For example, sand dunes along Triton Place,
Western Australia, have been stablisedand
preserved by planting marram grass.
• Limitation:
– However, human activities will need to be
minimised along the coasts in order to
preserve the sand dunes, hence this strategy
may not be effective in serving all coastal
communities.

EncouragingEncouraging
Growth of Coral ReefGrowth of Coral Reef
• Point:
– Coral reefs can be preserved or cultivated to
manage the coastline.
• Explain:
– Encouraging the growth of coral reefs is
effective as they act as natural breakwaters
that can weaken wave energy hence
protecting the coast against erosion.

EncouragingEncouraging
Growth of Coral ReefGrowth of Coral Reef
• Example:
– For example, the Maldives have invested
heavily in the cultivation of corals to protect
their economic interests along the coast.
• Limitation:
– However, corals are difficult to cultivate and
requires constant maintenance in order to
grow well.

3E 4E Coasts

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