Our Changing coastline

Coastal Processes

ErosionThe wearing away of the land/ cliff by the action of

the sea

TransportationThe movement of

eroded beach material by the wave e.g.

Longshore Drift (LSD)

Deposition

When waves lose their

energy they drop material

Types of erosion

Hydraulic Action The forces of the waves crashing

into the cliff. The air in cracks in the cliff is compressed which breaks up

the rock

Abrasion Waves carrying beach material e.g. sand and

rocks are thrown against the cliff wearing it away

Attrition rocks and pebbles collide with each

other and roll around. They

become smaller and more rounded

Corrosion (solution)

Is when the cliff dissolves by

slightly acidic water.

Waves

• Waves are created when wind blows over the surface of the sea.

• The fetch is the distance the wind has travelled over the sea before reaching the coast. (The bigger the fetch the bigger the waves)

• Water moving up a beach is called the swash and water moving back is the backwash

Waves

Constructive

• Strong swash• Weak backwash • Deposition occurs • Low wave frequency • Low wave height

Destructive

• Weak swash • Strong backwash• Erosion occurs • High wave frequency• High wave height

Types of waves

Coastal processes

Click on the link to watch the GCSE Bitesize video on coastal processes

Coastal landforms

• Lots of landforms are found along the coast, all have been created by either erosion or deposition.

Erosion Deposition

CaveArchStack Stump CliffWave cut notch Wave cut platform Headland and bay

SpitBarTomboloSaltmarshBeach

Erosion or deposition?

Cave, arch, stack and stump

• You may need to include processes of erosion.

How are caves, arches, stacks and stumps formed?

Caves, arches, stacks and stumps

The formation of caves, arches, stacks and stumps

Cliff and cliff retreat

• You may need to include processes of erosion.

How are cliffs and wave-cut platforms formed?

Headlands and bays• Headlands and bays are

formed where there are different rock types.

• The softer and less resistant rock will eroded away much faster than the harder and more resistant rock.

• This will form a headland where the harder rock are found.

• And a bay where the softer rocks are found.

• Much of the eroded material will be deposited in the sheltered bay forming a beach.

Headlands and bays

Longshore drift

• This is a type of transportation. • Remember that longshore drift is controlled by the direction

of the prevailing wind (which affect the angle the waves and swash move up a beach)

How is sediment transported along the coast?

Spit

• A spit is a depositional landform, created along coastlines where longshore drift occurs.

How are spits formed?

How are spits formed?

Coastal Landforms

Click on the link to watch the GCSE Bitesize video on coastal landforms formed by erosion.

Click on the link to watch the GCSE Bitesize video on coastal landforms formed by deposition.

How much do you know about coasts?

Affect people’s lives

• Over 17 million people live within 10 km of the UK coastline.

• Therefore coastal process and landforms impact on people’s lives.

• We have studied two ways in which coastal process and landforms affect people’s lives: -

1. Coastal erosion/ flooding 2. Tourism

Tourism

• The Dorset coastline is famous for the Jurassic Coast World Heritage Site

• Beach resorts located there are Bournemouth and Weymouth

• Some of the famous landforms are shown below: -

Old Harry

Durdle door Lulworth cove

Coastal path

Coastal Erosion – Holderness

• The Holderness coast is in the north east of England. This is one of the most vulnerable coastlines in the world and it retreats at a rate of one to two metres every year.

• The problem is caused by:• Strong prevailing winds

creating longshore drift that moves material south along the coastline.

• The cliffs are made of a soft boulder clay. It will therefore erode quickly, especially when saturated.

• Loss of farm land • Loss of houses and roads • Insurance policy increases

Management of the Coastline

• There are two main types of management on the coast.

• Hard engineering and soft engineering

• You may be asked to evaluate these (that means to look at the advantage and disadvantages)

Hard engineering Type of defencePros and cons

Sea Wall A wall built on the edge of the coastline. E.g Mumbles

AdvantagesProtects the base of cliffs, land and buildings against erosion. Can prevent coastal flooding in some areas.DisadvantagesExpensive to build. Curved sea walls reflect the energy of the waves back to the sea. This means that the waves remain powerful. Over time the wall may begin to erode. The cost of maintenance is high.

GroynesA wooden barrier built at right angles to the beach. E.g. Borth

AdvantagesPrevents the movement of beach material along the coast by longshore drift.Allows the build up of a beach. Beaches are a natural defence against erosion and an attraction for tourists.DisadvantagesCan be seen as unattractive.Costly to build and maintain.

Rip rap (rock armour) Large boulders are piled up on the beach. E.g Caswell

AdvantagesAbsorb the energy of waves.Allows the build up of a beach.DisadvantagesCan be expensive to obtain and transport the boulders.

Soft Engineering • Beach replenishment

– This replaces beach or cliff material that has been removed by erosion or longshore drift.

– The main advantage is that beaches are a natural defence against erosion and coastal flooding. Beaches also attract tourists.

– It is a relatively inexpensive option but requires constant maintenance to replace the beach material as it is washed away.

• Managed retreat – Areas of the coast are allowed to erode and flood naturally. Usually

this will be areas considered to be of low value - e.g. places not being used for housing or farmland.

– The advantages are that it encourages the development of beaches (a natural defence) and salt marshes (important for the environment) and cost is low.

– Managed retreat is a cheap option, but people will need to be compensated for loss of buildings and farmland.

How can the coastline be protected?Hard engineering techniques aim to stop coastal processes from occurring. Soft engineering methods try to work with nature to protect the coast.

Management of the coastline

Click on the link to watch the GCSE bitesize video about coastal management

Holderness coastal management

• The village of Mappleton, perched on a cliff top on the Holderness coast, has approximately 50 properties. Due to the erosion of the cliffs, the village is under threat.

• In 1991, the decision was taken to protect Mappleton. A coastal management scheme costing £2 million was introduced involving two types of hard engineering - placing rock armour along the base of the cliff and building two rock groynes.

• Mappleton and the cliffs are no longer at great risk from erosion.

• The rock groynes have stopped beach material being moved south from Mappleton along the coast. However, this has increased erosion south of Mappleton. Benefits in one area might have a negative effect on another.

Shoreline Management Plans

• In the UK local councils are responsible for management of the coastline.

• It is their responsibility to create a Shoreline Management Plan for their section of the coast.

• Local councils will need to make important decision about how different sections of a coastline may be managed.

• There are four main options• When making these decision

councils will have to weigh up the costs and benefits of protecting that part of a coastline

For and against management

• When decided whether to put sea defences in place. The following factors are considered: -

1. How many people are threatened by erosional and what is their property worth?

2. How much would it cost to replaces infrastructure such as roads and railway lines if they were washed away?

3. Are there historic or natural features that should be conserved? Do these features have economic value e.g. by attracting tourist to the area?

Sea Level Rise

• Sea levels are rising. • Over the past 100 year sea levels

have risen by 180 mm • The changes in sea levels are

thought to be a direct result of global warming.

• Also many parts of the UK are at increasing risk of sea-level rise because some coastlines are sinking.

Sea Level Rise

• Rising sea levels will result in increased erosion in places like the Holderness coastline. Increase risk of flooding in vulnerable areas such as Jaywick in Essex and some countries may even by underwater in the next 100 years for example the Maldives.

• This will make some of the decisions being made along the coastline even more important.

Sea Level Rise

• One way the UK has planned to deal with sea level rise along the Thames estuary is the building of the Thames Gateway.