COASTAL LANDSCAPES

By Badir

DESTRUCTIVE WAVESCharacteristics: Backwash is much stronger than its

swash, therefore it carries sediment away from the shore.

The break frequently, between ten to fifteen every minute.

High in porportion to their length. There are generally found in steep

beaches

These types of wave are responsible for coastal erosion.

CONSTRUCTIVE WAVESCharacteristics: The swash is more powerful than the

backwash, therefore it deposits sediment on the beach.

The break infrequently at rate of ten or fewer per minute.

They are long in relation to their height. They are usually found on gently sloping

beaches.

This type of wave is responsible for depostition.

TYPES OF EROSIONHydraulic action: Pressure of water being

thrown onto a cliff.Corrasion/Abrasion: Sand and pebbles

scrape are thrown against the cliff and they scrape it therefore causing erosion.

Corrosion: A chemical rection between the ock and the salt and the other acids in seawater. Eg Limestone.

Attrition: When boulders and rock bang into eachother it causes them to lose parts of the rock because they are being chipped off.

TYPES OF WEATHERINGPhysical weathering: (Freeze Thaw) This is

when water gets into cracks in the rock. When the temperature falls below 0 degrees it freezes, therefore the water will expand as it turns to ice. As a result this would add pressure to the surrounding rocks and causing them to break off.

TYPES OF WEATHERINGChemical Weathering: Rain water contains

weak acids (Sulfur dioxide and Nitrogen oxide) these can react with certain rocks. The carbonates in limestone are dissolved by these acid and this causes the rock to break up and disintegrate.

TYPES OF WEATHERINGBiological Weathering: This is the action

of plans on animals on land. When seeds fall into cracks and grow the roots of the plant put pressure on the rock and therefore break the rock. Burrowing animals such as rabbits can also be responsible for further damage to the rocks.

MASS MOVEMENTBasically the movement of material down

a slope due to the pull of gravity.Slumping: During dry weather the clay

contracts and cracks, when it rains water gets into the cracks and rock absorbs it until it is saturated. This weakens the rock and due to the pull of gravity it slips down the slope in a rotational movement. This is most common on the coast.

MASS MOVEMENTSoil creep: This is the slowest downhill

movement of material. It happens when water on the slope is frozen therefore it expands causing the material to stick out at an angle. Then when it is warmer it turns back into water but due to the pull of gravity it falls at a 90 degree angle. This leaves terracetts behind

HEADLANDS AND BAYSOn coastlines where the resistance of rocks varies. The headlands are the ones that stick out onto the sea since they are more resistant therefore it is takes longer for it to be eroded. However the bay is made of a less resistant rock therefore it erodes more easily. After a while when the bay has retreated back the waves would be breaking on the headlands first therefore they would now be experiencing a lot more force therefore they erode quickly now.

CLIFFS AND WAVE-CUT PLATFORMSWhen the force of the sea attacks the base of a cliff (Hydraulic action and abrasion) it undercuts the cliff forming a wave cut notch. Above this an overhand has been formed after a long period of time due to the weight and pull of gravity the overhang will fall (sometimes due to weathering also) . As this process repeats itself the cliff will retreat. The rocks will fall into the sea creating a platform, overtime the width ofthe platform increases therefore the power at which the waves hit the cliff decreases.

CAVES, ARCHES, STACKS AND STUMPSThese are formed in rocks that a have a fault

or line of weakness. The fault will be exploited due to the sea (hydraulic action). Over a certain period of time the fault will widen to form a cave. After continuous erosion caves from both side meet forming an arch. The sea will continue to erode the bottom of the arch, and weathering will weaken the rock. Over time the rock will fall down due to gravity and its weight. This leaves a column of rock called a stack. Continued weathering and erosion will develop the stack into a stump.

LONGSHORE DRIFTIt is the movement of sand and pebbles

down a coastline. The direction of the prevailing wind determines the angle at which the swash will hit the beach. The backwash will be perpendicular due to gravity. Due to this process material is transported down the beach. Long shore drift creates landforms such as spits and bars

BEACHESA beach is an area of land between the

low tide and storm tide marks, it is made up

of sand and pebbles. They are often formed

in bays where the swash is weak therefore material is deposited.

SPITSA spit is a long narrow stretch of pebbles

and sand which is attached to land at one end. It forms due to long shore drift. This is because when the coastline ends, the sea deposits the material it was transporting. If there is a river estuary then the waves and river cause a change in speed which cause both the river and sea to deposit its material. Overtime the material builds up and forms a spit. Salt marshes are formed in the side of the spit closer to the coast.

BARSIf a spit develops in a bay it may build

across it linking two headlands to form a bar. However this is only possible if there is a beach with a gentle slope and no river entering the sea.

COASTAL RECESSION The North Norfolk coast’s new shoreline

manage plan consists of a managed retreat which means that 1000 homes, 1400 caravan and chalet parks, six hotel and hotels, seven historic building, 3.5km of road, seven golf course holes and three community halls will be lost to the sea over the next 100 year. The government will save 41 million pounds by not building coastal defenses. However the estimated economic cost will be 100 million pounds and 357 million pounds for tourism.

PREDICTION AND PREVENTIONThe met office predicts how likely a

coastal flood is to happen. Also the environment agency has a website which warns people when floods may happen.

www.Direct.gov.uk educates people on how to protect homes from flooding and how to react to a flood.

DEFRA provides money for coastal flooding protection.

Also building design can help reduce effects of coastal flooding.

HARD ENGINEERINGRip-rap: They are large rocks placed in

front of the cliff. Advantages: Very cheap, effective for

many years, and reduce the energy of the waves.

Disadvantages: Can make the beach inaccessible, unattractive and not effective in storm conditions.

HARD ENGINEERINGRecurved sea wall: Walls usally made with

concrete.Advantages: Reflects and absorbs wave’s

energy, effective for many years and its very visible therefore it makes residents feel safe.

Disadvantages: Ugly and makes tourists angry, expensive to build

HARD ENGINEERINGGroynes: Usually made from wood

stretches from the coastline into the sea.

Advantages: Prevents long shore drift (sand builds up on one side of the groyne, it keeps beaches in place for the tourist industry and it is effective for many years.

Disadvantages: Unattractive and difficult to walk over and it disrupts the natural process of long shore drift which effects area down the coast because they won’t have as much sand.

HARD ENGINEERINGGabions: Wire cages filled with stone used

to reduce erosion.Advantages: Cheaper than other forms of

coastal defence and the rock cages absorbs the waves energy.

Disadvantages: Wire cages can break and they are not as efficient as other forms of coastal defence.

HARD ENGINEERINGOffshore reef: Large concrete blocks and

natural boulders are sunk offshore to alter wave direction and to dissipate the energy of the waves.

Advantages: The waves lose energy when they hit the offshore reefs therefore less erosive power and they allow the build up of sand.

Disadvantages: May be removed by heavy storms and difficult to install them.

SOFT ENGINEERINGBeach replenishment: The placing of sand

and pebbles on a beach.Advantages: Looks natural, provides

beaches for the tourists, a beach is the best form of natural defence because it dissipates wave energy and its cheap.

Disadvantages: The scheme requires constant maintenance, it can all be wash away very quickly in less than a year and it creates a loud nice as large lorries full of sand reularly replenish beach.

SOFT ENGINEERINGCliff regrading: The cliff is cut back and

given a new gentle slope to stop it slumping,

Advantages: It may be covered in ecomatting to encourage vegetation growth and it is very natural therefore it will encourage wildlife.

Disadvantages: It is not effective by itself it will need extra defence at the bottom of the cliff and some homes on the cliff may have to be demolished.

SOFT ENGINEERINGManaged retreat: Allowing the sea to

gradually flood land or erode cliffs (North of Norfolk).

Advantages: Creates new habitats for plants and birds and it is cheap.

Disadvantages: Upsetting for land owners who lose land and it is difficult to estimate the extent of sea movement especially with rising sea levels.