Coastal Studies

Coastal studies

What is a coast?

• A coast is the zone where the land and the sea meets

What causes the changing of the coast?

• The coasts are ever changing as they are shaped by many agents.

• The action of • Waves• Currents• Winds• People• The growth of coral reefs

The action of waves

• When the wind blow across water bodies such as seas and oceans, they cause rising and falling of the water surfaces. These movements of rise and fall is called WAVES

The formation of waves

wave motion

Energy of the waves

• Waves have energy• High energy when the waves push forward• Low energy when the waves lapping gently along

the coast.

Factor affecting the wave energy

• There are several factors that influence wave energy.

• One of the factor is WIND• The higher the speed of the wind, the higher the

wave energy will be. • Another factor is FETCH• Fetch is the distance of open water which the

wind blows.• Long fetch will cause the waves have high energy.

FETCH

SWASH

• The white foamy water that rushes up the coast is called SWASH

• The SWASH carries the materials up the coast.• The friction and the pull of gravity then cause

the water to flow back towards the sea.

BACKWASH

• The flow back to the sea after the wave have broken is called BACKWASH.

• The backwash will carry some material back to the sea.

CONSTRUCTIVE WAVES

CONSTRUCTIVE WAVES

• Constructive waves are low energy waves that deposit materials on a coast.

• As the waves approach such as coast, the friction between the waves and the sea bed causes the waves to slow down at some distance from the coast.

• The waves break gently over a long distance.• Swash is powerful than backwash, the more materials

are carried up and deposited on the coast than are removed.

• Over time, the coast is built up.

DESTRUCTIVE WAVES

DESTRUCTIVE WAVES

• Destructive waves are high energy waves that’s erode a coast .

• They are common along steep sloping coasts where they are break with a great force over a short distance.

• The backwash of the waves is more powerful than the swash.

• More materials are removed than are deposited on the coast.

• Over time , the coast is eroded away.

CURRENTS IN ACTIONWhat is Current?• Currents are flows of water that move either

horizontally or vertically in a certain direction.• Currents such as longshore currents help to shape

the coast.What is Longshore current?• Longshore currents are water that flow parallel to a

coast and are formed by waves that approach the coast at an angle.

• Longshore currents are important in transporting amount of materials can build up the coast.

Winds in action• Winds form waves and longshore current which shape the

coast. • Winds can change the coast too.• For example, wind transport sand and deposit them along

the coast to form certain features.

How do the coast change?

• Coastal erosion- There are four types of coastal erosional

process similar to those of the river.- Hydraulic action- Corrasion- Attrition- Solution

Hydraulic action• When waves hit the coast repeatedly, they weaken the rocks,

break them and carry them away. • Water enters the rock lines of weakness such as joints and

fault.• The air inside the rocks become trapped and is compressed

by the water.• The compressed air exerts pressure on the joints and faults

and when the waves return to the sea, there is a sudden release in pressure.

• The rock expands with great force and widen the joint and faults.

• Repeating process of expansion and compression eventually cause the rocks to break into smaller pieces.

HYDRAULIC ACTION

CORRASION/ABRASION

• When materials are carried by waves are thrown repeatedly against the coast.

• They are gradually erode the coast.

ATTRITION

• When materials are carried away , they collide with one another.

• Eventually, the materials break down into smaller pieces and become smoother and more rounded over time.

SOLUTION

• Water in the waves reacts chemically with the soluble minerals in the rocks along the coast and dissolves them.

• Limestone coast when react with seawater dissolves.

Animation of coastal process

Factors affecting the rate of erosion• The type of wave- Destructive waves cause more erosion than constructive waves. - Backwash is more powerful than swash.- More materials are carried away from the coast than are

deposited on it.

Factors affecting the rate of erosion

• Position of coast-Coast are not protected from prevailing winds

are more exposed to wave action than sheltered coasts.

Factors affecting the rate of erosion

• Natural of coastal rock- Rocks that are made of different resistance to

erosion depending on the mineral composition of the rocks and the presences or absences of lines of weakness.

- Coasts made of granite and basalt( hard rocks) are more resistant to erosion than shale and clay (soft rocks)

EROSIONAL FEATURES

• CLIFFS AND WAVE-CUT PLATFORMS• HEADLAND AND BAYS• CAVES, ARCHES AND STACKS

CLIFF AND WAVE CUT PLATFORM

CLIFF- is a steep rock face.

WAVE CUT PLATFORM- A gently sloping rock surface which extends

towards the sea from the foot of the cliff.

The formation of cliff and wave-cut platforms

Formation of cliff and wave cut platform

1. Wave erosion along a line of weakness produces a cut called a notch on the coast.

2. The notch is further eroded to form a cave, a hallow with an opening in a mass of rock.

3. Further erosion causes the overhanging part of the cave to collapse into the sea and a cliff is left behind.

4. Continuous erosion causes the cliff to move back or retreat inland. Over time, a wave-cut platform is formed at the foot of the cliff.

Animation of cliff and wave cut platform

HEADLAND AND BAYS

HEADLAND- A STEEP ROCK FACE WHICH PROJECTS INTO

THE SEAS

BAYS- A WIDE CURVES OF LAND ALONG THE COAST

WHICH ENCLOSES PART OF THE SEA.

HEADLAND AND BAYS

FORMATION OF HEADLANDS AND BAYS

• THIS IS THE RESULT OF TWO ALTERNATING BAND OF HARD ROCKS AND SOFT ROCKS WHICH ARE ARRANGED AT RIGHT ANGLE TO THE COAST.

• WHEN THE WAVES ERODED THE SOFT ROCKS IT FORMS BAY AND THE HARD ROCKS IT FORMS HEADLANDS.

Animation of headland and bays

Caves, Arches and Stacks

Caves – is a hollow with an opening in a mass of rock.

Arch- is a bridge of rock above an opening.

Stack- is a pillar of rock left behind after an arch collapses.

The formation of caves, arches and stacks

• Wave erosion along a line of weakness on the headland to form a notch

• The notch is further eroded to form a cave• The cave is continually eroded until a hole is cut

through the headland and an arch is formed.• Further erosion of the arch causes it to collapse

, leaving behind the stack which is a left standing in the sea.

Animation of cave, arch and stack

Transport along the coast

• The materials that are eroded from the coast are usually transported along the coast by waves and currents before they are deposited elsewhere.

The Longshore Drift

• When waves approach a coast at an angle, the swash brings the sediment up onto the coast at the same angle.

• Due to friction and the pull of gravity, the sediment is then brought seawards by the backwash at a right angle to the coast.

• The sediment is picked up again by the next wave and carried up and then down the coast again.

• This repeated zig zag movement of the sediment shifts the sediment along the beach.

• A long shore drift is the movement of sediment along the coast when waves approach the coast at an angle

Animation of long shore drift

Depositing along the coast

• Deposition occur along the coast due to the • -constructive waves which have a more powerful

swash than backwash, more materials are deposited than eroded on such coasts.

• - when the coasts are sheltered from prevailing winds which protected from wave erosion and deposition of materials take place.

• -Storm also subsidies, the large amount of materials eroded from the coast than transport away from the coast. Hence, these materials are deposited.

Depositional features

• Beaches• Offshore bars• Spits and tombolos• Coastal dunes

The formation of Beaches

Beach is a zone of materials accumulated along the coast.

The formation of Beaches

A beach is formed when deposited materials carried by waves are accumulated in a zone along the coast. The materials on the beach vary in size from fine sand to pebbles . The waves sort these materials according to the weight. The finer sand deposited nearer the sea and the coarser materials further inland.

Offshore bar

Off shore bar is a long narrow ridge of deposited materials sand can be found lying away from and parallel to a coast.

The formation of offshore bars

• When the waves approach a gently sloping coast , friction between the waves and the sea bed causes the waves to break at some distance from the coast.

• Over time, more materials are built up parallel to the coast to form ridge of sand called offshore bar.

• A body of coastal water may be partially or completely cut off from the open sea by the offshore bar. The body of water is called a lagoon.

Spits and Tombolos

• A Spit is a long, narrow ridge of deposited materials that extends from the mainland into the sea. An example in Brunei is Muara Spit and Kuala Tutong Spit.

• When the spit is connected the island to the mainland to form a feature is called the Tombolos.

The formation of Spit and Tombolos

1. The long shore drift transports materials along the coast. If there is a sudden change in the direction of the coast, the longshore drift continues to transport the materials in the original direction to the deep sea

• 2. As the longshore drift enters the deep water, the materials are deposited. Over time, these materials accumulate above the water to form a spit.

• 3. The spit continues to grow with the continuous deposition of materials.

• 4. The spit join a nearby island to the mainland to form a tombolo.

Coastal Dunes

A coastal dune is a ridge of sand that is piled up by the wind on the coast.

The formation of coastal dunes

• Coastal dunes are formed due to large supplies of dry sand and experience prevailing winds.

• Winds blow and pile up sand on the coast further inland to form a crescent shaped coastal dune with a concave side facing the wind.

• Wind may also form straight coastal dunes that are deposited at right angles to the wind.

People and Coast

Coastal development are for• Port activities• Tourism • Settlement• Industries• Farming

Port Activities

• Coasts which are sheltered from storms and have deep waters in which ships can anchor are suitable for development as PORT.

• Some are strategic location and accessible by different sea routes.

• Examples the port of Singapore and the port of Yokohama in Japan.

Tourism

• Some coast are attractive to holiday makers.• Coasts which have crystal clear water, long

stretches of wide sandy beaches and have beautiful coral reefs often developed as beach resort. Examples of coasts Pulau Langkawi & Phuket

• Some coast have interesting features as headland, caves , arches, stack and cliffs. Example Twelve Apostles in Victoria, Australia

Land reclamation

Land reclamation where land is in short supply, people may create additional land along the coast. Such as in Singapore and the Netherlands.

These land are used for farming activities such as cattle rearing and cultivation of crops such as wheat and barley.

Apart from that also, they use it as settlement consist of farmhouse, villages, towns and cities.

Coastal Problems

• Flooding and erosion are two common problems along the coastal area.

• These problems effect both the environment and people.

• As the result of this, the coastline retreat inland and the coast become unsuitable for settlement, tourism and industry.

Coast flooding Project

• The Delta Projects in the Netherland is to control the flood

• Because of flooding activities the coastal experiences of loss of life and property damage.

• Dams and storm surges barrier were built to keep out seawater in times of floods.

Coastal Erosion

• One measure taken place to protect the coast from erosion is to build structures such as seawall, breakwaters and groynes.

Seawalls

• Is built on and parallel to a coast. It protects the stretch of the coast behind it by reflecting waves away from the coast.

Sea walls

breakwaters

• Built with one end and attached to the coast.• Protect the coast by breaking the force of

oncoming waves at some distances

breakwaters

groynes

• Are built at right angle to the coast .• Groynes interupt the longshore drift and

causes materials to deposit on side of the groynes facing the longshore drift.

Groynes