3e 4e coasts

CoastsCoastsCoast 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 Coastal Factors Affecting Coastal EnvironmentsEnvironments

1. Waves2. Tides and sea level changes3. Currents4. Geology5. Types of ecosystems6. 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.

CoastsCoastsWaves


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 InfluencingWave Energy Wave Energy

1. Wind speed2. Duration of wind3. 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

Tombolo

Waves and LandformsWaves and Landforms

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

Headland

Shore platform

Sea cave

QuizQuiz

• Compare the difference between constructive waves and destructive waves.

[3]

CoastsCoastsWave Refraction


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.

CoastsCoastsCoastal Processes


1. What are coastal processes?


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

Coastal ProcessesCoastal Processes

1. Erosion2. Transportation3. 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 or Abrasion 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.

AttritionAttrition

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]

CoastsCoastsCoastal 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.

Blue Grotto, Italy

CavesCaves

• Waves attack lines of weakness and undercut the base of headlands.

• Continuous action of waves hollowed out the headland, forming a cave.

Cabo San Lucas

ArchesArches

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

12 Apostles, Australia

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]

CoastsCoastsCoastal 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 services2. Regulating services3. Cultural services4. 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 seafoodb. Waterc. 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 stabilizationb. Flood preventionc. 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 benefitsb. Aesthetic benefitsc. 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 habitatb. 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.

CoastsCoastsPeople and Coastal Areas

By the end of the lessonBy the end of the lesson

We will be able to1.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 aquaculture2. Housing and transportation3. Tourism and recreation4. Ports, harbours and piers5. Wind farming6. Desalination7. Sand mining, salt extraction8. 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.

Kukup, Malaysia


• 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

Lillgrund Wind Farm Sweden


• 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.

CoastsCoastsCoral Reef Ecosystems


1. Why are costal reef ecosystems distinctive and valuable?

2. What pressures are coral reefs facing?


We will be able to1.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 ecosystems2. Absorbs wave energy3. Serves as tourist attractions4. 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. Overfishing2. Irresponsible fishing methods3. Recreational use of coast4. Pollution5. Siltation6. Costal development7. Climate change

TaskTask

• Describe two pressures faced by coral reefs.

[2]

CoastsCoastsMangroves Ecosystems


1. Why are mangroves ecosystems distinctive and valuable?

2. What are the pressures on mangroves?


We will be able to1.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.


• 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 the Adapting 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.


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


• Trees such as the 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 shorelines2. Breeding ground and habitat3. Wood for fuel4. 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 charcoal2. Need for more farming areas3. Land reclamation4. Water pollution5. Rising sea level

CoastsCoastsThreats to coastal areas


• What are the threats to coastal areas?


We will be able to1.Identify and explain the threats to coastal areas.

Threats to Coastal AreasThreats to Coastal Areas

1. Climate change2. Eroding shorelines3. Rising populations4. Coastal development and habitat loss5. 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.

CoastsCoastsSustainable Management of Coastal Areas


1. How can coastal areas be managed?


We will be able to1.Evaluate the effectiveness of strategies to achieve sustainable management of coastal areas.

Sustainable Management Sustainable Management of Coastal Areasof Coastal Areas

1. Limit damaging activities2. Protect coastal resources3. 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.

Goat Island, New Zealand


• 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.

CoastsCoastsCoastal Protection Measures


1. What are the coastal protection measures?


We will be able to1.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 engineering1. Beach nourishment2. Planting vegetation3. Stabilizing sand dunes4. Encouraging growth of coral reef


• Hard engineering– The construction of physical structures to

protect coasts against the erosive power of waves.


• Hard engineering1. Seawalls2. Gabions3. Breakwaters4. Groynes5. 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.

Encouraging Encouraging 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.

Encouraging Encouraging 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.

ENDEND

3e 4e coasts

Documents

coastal erosion

coastal ecosystems

coastal environmentswavestides

coastal processes of

coastal environments

intensity of coastal

activity of coastal

impact of waves