Geography - Coasts

Constructive Waves 

They are low waves that surge up the beach with a powerful swash bringing in material but receed with a weak backwash therefore not bringing back any material off the beach. They carry and deposit large amounts of snad and shingle contructing the beach. These are formed through storms very far away.

Destructive Waves 

These are formed by local storms close to the coast and can erode the beach due to their strong backwash and weak swash. Thay are usually closly packed cuasing an interfearance making a mass of swirling water. Before hitting the beach they become steep and curl around. 

Solution:

Dissolved materials from alkali rock like limestone or chalk, when the acidic water evapourates the rock is left transporting the material somewhere else.

Suspension:

Particles carried - suspended - within the water and then taken to anther location.

Saltation:

A hopping or bouncing motionof partiles too heavy to be suspended inn the water.

Traction:

Where large pebbles are rolled along the seabed.

Hydraulic Action 

Trapped air is forced into holes and cracks in the rocks and then compressed eroding the cliff . The explosive force is called cavitation.

Abrasion

This is the sandpaper affect because the pebbles grind over the platforms making it smooth.

Attrition

Rock fragments suspended in the water smahs against each other casue them to become smaller and smaller.

Solution

The dissolving of rocks due to the acidity of water meaning chalk and limestone - alkali rocks - will be eroded easily 

Corrasion 

fragments of rocks are picked up and thrown at the cliff, this acts like tools scraping away the cliff slowly.

Freeze thaw (mechanical)

Water collects in cracks inside the rocks, when it freezes thermal expansion occurs makign the ester expand weakening the rock. Fragments of rock may be broken off when this happens.

Salt Weathering (mechanical)

When salt water evapourates salt crystals are left over, these depositscan increase in size causing flaking and breakign of rock.

Carbonation (chemical)

Rainwater absorbs carbon dioxide becoming acidic, contact with alkali rocks causes a chemical reaction (dissolving).

Biological Weathering

Due to the actions of fauna and flora cracks can form in rocks from this like roots expading and aimals makign burrows into the soil weakening the cliff.

Onion skin weathering

This is where the temperature causes layers of rock to peel of the cliff surface weakening and eroding hte cliff face.

The large scale downward movement of debris under the influence of gravity.

Rockfall

Fragments of rock breakaway from the cliff face due to freeze thaw weathering 

Landslide

Masses of debris moving down a slope, the accumulated material put stress on the ground makign it have less friction.

Rotational slip/slump

Slump of saturated soil and weak rock along a curved surface.

Mudflow 

Saturated soil and weak rock flow down a slope.

Longshore drift 

The movement of sediemnt across a coast depending on the direction of the prevailing wind. The waves approach the coast at an angle and then retreat perpendicular to the beach. this process often coases erosion  #but also depostion because of the swash bringing material but the backwash taking away material. It can lead to many landforms : tombolo, spit, bar....

Headlands and Bays 

Different types of rock erode at different rates. Weaker bads of rock like clay erode faster than rocks like chalk. The faster eroding material forms bays because of the recceded point whereas the slower eroding part is the headland as it pertrudes out of the cliff. Bays are sheltered by the headlands and are more likely to form snady beaches. On the other hand erosion is high on the headlands whihc is why there arn't any beaches.

Case Study

Bridlington Bay -  South Coast Of England (boulder clay)

Flambourough Head - South Coast Of England (chalk)

Caves 

The energy of the waves wear away the rock along the line of weakness forming a cave in the headland.

Arches 

Erosion may lead to two back to back caves resulting in an arch (a hole through the entire headland).

Stacks 

Overtime the arch is enlarged and processes liek weathering (biological and freeze thaw) weaken the roof causing it to collapse., resulting in a stack : a part of rock which is far away from the intial headland.

Stumps 

The stack is eroded through multiple processes liek corrasion and attrition lead to it collapsing leaving a stump.

Wave cut platforms

The area left from a receeded clif is the wave cut platform. It is usually smooth from processes like abrasion.

Sandunes

Embryo dunes are formed around deposited pieces of debris such as rocks or wood.

These develop and become stabilised with vegatation to form fore dunes and yellow dunes. Marram grass is adapted to these conditions (windy and exposed and has long roots to find water). The roots bind the sand together stabilising the dunes.

Rotting vegataion adds organic matter to the sdand making it more fertile. therefore more colonies of plants develop on the beach in the grey and mature dunes.

Wind may form depressions in the sand making dune slacks which can contain ponds becuase they are below sea level (water table).

Beaches 

Beaches are deposits of sand and shingle. Sandy beaches are usually located in sheltered bays away from destructive waves. The waves entereing the bays are constructive waves meaning they build the beach and do not erode it. Whereas shignle covered beaches are more likely to be in the south coast because of the high energy environments. The destructive waves wash away the sand but leavre behind the shingle. It comes from eroded cliffs further down the coasts.

The waves enter the bay and lose energy due to the shallow and sheltered area then become constructive. This means they have a strong swash and a weak backwash ideal for depositing material. This sediement accumulates overtime causing the beach to become sandy and extend further out making it good for tourism and other businesses to thrive. An example of this is the Holderness Coast towards the South coast of England.

Berms

The line on a beach where high tide reachess leaving rubbish and seaweed.

Spit

A spit is a long narrow finger of land caused by longshore drift.

Spits form on the coast where there is significant longshore drift occuring. If the coastline changes direction or orentation sediment is depostied out to sea. As it accumulates an extension of land forms from the lan. this process continues gradually growning it further and further until strong winds or tidal currents cause the edn of the spit to curve and make a feature called a recurved end. 

This can be identified at Spurn Point along the Holderness coast on the south coast where the wind directions are north east.

Saltmarsh 

The sheltered water behind the spit becomes a saltmarsh because of the depostis of mud. Vegatation starts to grow on the saltmarsh making it really important wildlife habitiats and ecosystems.

Bar

Longshore drift may cause a spit to grow across a bay due to the change in direction of the coast. The trapped area of water is known as a lagoon.

Devon, Slepton Ley (South coast of England)

Tombolo

A tombolo is were longshore drift carries sediment and consistently deposits it due to the friction created and the change in orentation of land or direction. The accumulation of this sediment leads to a spit being formed which eventually reaches towards an island.

Dorset, Chesil Beach (South coastof England)

Hard Engineering

Using artificial structures such as sea walls to control natural processes to protect the coast, local businesses and homes.

Hard engineering methods 

Rip Rap, Wooden groynes, Gabions, Sea wall and Wooden revetment.

Soft engineering 

Less intrusive, more environmentally friendly methods that work with the natural proceses to protect the coast, local businesses and homes.

Soft engineering methods

Beach nourishment, Sand dune regeneration, Dune fencing, Cliff stabilisation and managed retreat 

Rip Rap

Piles of large boulders are dumped at the foot of a cluff. the rocks force the waves to break absorbing their energy and protectign the cliffs from erosion. The rocks are generally brought by barge to the coast.

Cost : £2000 per meter 

Pros 

Relativly cheap and easy to maintain

Can provide interest to the coast, and can be used for fishing

Cons

The rocks generally dont fit in with the local geology.

Can be obtrusive.

Rocks are either from other parts of the coastline or abroad and can be expensive to transport.

Walton on the Naze, Essex 

Wooden groynes

Timber or rock structures built out to sea from the coast. they trap sediment being transported by longshore dirft and make the beach bigger by doing this. The wider beach acts as a natural buffer to reduce wave damage makign anotehr sea defence.

Cost: £750 per meter 

Pros

Creates a wider beach which attracts tourism and can provide useful structures for fishing.

Not too expensive 

Cons 

As longshore drift is interrupted areas furter down the coast dont get any sediment but erosion still occurs meaning mass erosion occurs. The problem is then shifted not reesolved.

Groynes are unnatural and rock groynes can be really unattractive.

Eastbourne, Sussex 

Sea wall 

This is a concrete or rock wall against the sea, normally placed at the bottom of cliffs to prevent the undercutting of the clif. It also has a curved surface to reflect any waves back into the sea.

Cost: £5000 - £10000 per meter 

Pros 

Effective at stopping the sea from eroding the coast.

Often has a walkway or promanade for people to walk on.

Cons 

Can look obtrusive and unnatural 

Very expensive and there is high maintenance costs.

Holderness Coast, Withernsea

Gabions 

They are wire cages filled with rocks that can be built to support a cliff or provide a buffer against the sea.

Cost: £500 per meter

Pros 

Cheap to produce and flexible in fina; design 

Can improve drainage of the cliffs 

Will eventually become vegatated and merge inot the landscape 

Cons

For a while they look unattractive 

Cages only last 5-10 years before they rust and become weakened 

Thorpeness, Suffolk

Wooden revetment

Wooden fence-like structures that allow sea water and sediment to pass through, but the structures absorb wave energy. A beach can build up behind the revetment and provide further protection for the cliff. 

Cost: £1500 per meter

Pros 

Effective at breaking the force of the waves (absorbing the wave energy)

It creates a bigger beach behind the revetment, the bigger beach provides and attracts areas for tourism

Cons

Environemntally unsightly

Doesn't give total protection to the base of the cliff 

May need replacing quickly.

Happisburgh, Norwich

Beach nourishment

This is where sand or shingle is added to a beach to make it higher or wider. The sediment used is normally obtained through another location offshore therefore blending in with the existing beach. it is generally transported on a barge.

Cost: £5000 per meter 

Pros

Relativly cheap and easy to maintain.

Blends in with the local environment 

Increases potential tourism by creatign a bigger beach 

Cons 

Requires constant maintenance due to longshore drift unless structures are built to retain the beach material

Eastbourne, East Sussex 

Sand dune regeneration

Sand dunes are effected by buffers to the sea but are easily destryed and damaged. Marram grass (adapted to the harsh conditions) can be planted to stabilise the dunes therefore helping them to develop.

Cost: £2 - £20 per meter 

Pros 

Maintains a natural coastal environment that is popular with people and wildlife 

Relativly cheap 

Cons 

Time consuming to plant the marram grass and fence areas off.

People dont like to be prohibited from certain areas 

Can be dmaaged by storms 

Chichester, West Sussex

Dune fencing 

Fences are constructed seaward facing of existing dunes t oencourage new dune formation These new dunes protect the existing dunes from being dmaaged or destroyed.

Cost: £2 - £20 per meter 

Pros 

Minimal impact on natural systems 

Can control public access to control other ecosystems 

Cons 

Can be unsightly especially if some of the fences are broken.

Regula rmaintenance needed mainly after storms 

Formby, Merseyside

Cliff stabilisation

This means reprofiling and planting vegetation therefore supporting the slope with the plant roots making it more sturdy and resistant to erosion. The reprofiling makes it so the waves go along the sloep instead of undercutting a cliff. 

Cost: £10 - £200 per meter 

Pros 

Blends in with the environment and builds ecosystems and habitats

Provides potential tourism attractions builind local businesses.

Effective at protecting the coast and cheap

Cons 

Changes the environment and during the process pof making it could harm ecosystems or wildlife

It may take a while to develop the vegataion and if there is a storm it may need maintenance.

Mapleton, Holderness Coast

Managed retreat 

It is the policy of allowing the sea to flood or erode an area of relativly low value land. This reduces the cost of sea wall repairs and builds making it cheap in the long term but als ocreates a saltmarsh therefore making a natural sea defence. 

Cost: £28million 

Pros

No maintenance costs becuase it is sustainable and provides a natural sea defence

Astetically pleasing and ecosystems are developed attracting tourism

Cons 

Valuble land is lost 

Really expensive intial costs, housing costs, farmland costs 

People are forced out of their homes and some have their land forced of them for money

Medsmerry, West Sussex