There are two types of waves
Waves as strong as these onlyoccur in severe storms. They can cause terrific damage to coastal settlements as well as causing a lot of erosion.
The amount of erosion which takes place depends upon: The strength of the waves The strength of the rock
Constructive waves lead to the formation of beaches.Beaches are the most common feature of deposition.
What processes shape our coastline?
What processes shape the coastal zone?Weathering processesMass movementCoastal processes
Weathering processesWeathering is the disintegration of rocks in their original placeFreeze-thaw is particularly effective in the coastal zone if the rock exposed is porous and / or permeable.
The rocks are broken down in situ, which means that no movement is involved, unlike erosion which is caused by the movement of water, wind and ice.
Rock fall - Beachy Head, East Sussex, 12/1/99During an exceptionally wet period the chalk rock became saturated with water. Long periods of frost weakened the rock leading to several dramatic rockfalls along the south coast of England.
Mass MovementMass movement is the downhill movement of material under the influence of gravity
Both mass movement and weathering provide an input of material to the coastal system.Much of this material is carried by the waves to be deposited elsewhere along the coast.
Hydraulic Action AbrasionSolutionAttritionWhen waves throw beach material at the cliffWhen eroded material is broken down into smaller piecesPressure from air trapped in crackscauses rocks to breakLimestone & chalk react with the sea which is a weak acid.
What processes are at work to create this landscape?AbrasionAttritionHydraulic actionSolutionFreeze-thawweatheringSolutionBiological weathering
Headlands and Bays
Cliffs and wave cut platforms
The waves attack the base of the cliff through the processes of hydraulic action, abrasion, and solution. Over time the cliff will be undercut and a wave-cut notch is formed. Eventually the cliff becomes unstable and collapses. Further cliff retreat will leave a rocky wave-cut platform.Wave-cut platform
Wave cut platform
Wave cut platformcliffs
Caves, arches and stacks
Marsden Rock in 1984
Flamborough HeadBoulder clayHullSpurn PointFormer coastlineEuropes fastest eroding coastlineNorth SeaR.Humber
HeadlandCliffArchWave cut platformStump
Crumblingboulder clay cliffsRotational slump
North SeaRiver HumberSpurn Point
This movement of sediment along the coastline is called longshore drift.Direction of movementswashbackwashBackwash is always at right angles to the beachCoastal Processes - TRANSPORTATION
BeachesBeaches are accumulations of sand and shingle found where deposition occurs along the coast. Sandy beaches are often found in sheltered bays, where they are called bay head beaches
Pebble beaches tend to form where cliffs are being eroded and where there are high energy waves.
As constructive waves build up beaches, they often form ridges in the beach known as BERMS. The berm highest up the beach represents the extent to which the water has reached during high tide.
A spitA spit is a long narrow finger of sand or shingle jutting out into the sea from the land
Spits only develop in places where:Longshore drift moves large amounts of material along the coast.There is a sudden change in the direction of the coastline.The sea is relatively shallow and becomes progressively more sheltered.
HullR.HuThe Formation of Spurn PointErosion of the coastlinenorth of Spurn PointEroded material transported by sea currentsMaterial dropped where coastline changes directionSpit grows out from coast as more material builds up.End of spit curved by action of the wavesFormer coastlineHULLRIVERHUMBER
A barOccasionally, longshore drift may cause a spit to grow right across a bay, trapping a freshwater lake or lagoon behind it. This feature is called a BAR. E.g. at Slapton Ley in Devon
Example:The East Coast of Yorkshire- The Holderness Coast
Causes of cliff collapseThe cliffs along the Holderness coastline are made of boulder clay. Apart from wave erosion, weathering processes also contribute to cliff collapse.Most cliff collapse occurs during or after prolonged heavy rain when water seeps into the land surface.It saturates the clay and makes it heavy. The added weight causes the clay to move. This causes landslides and slumping to take place along a slide surface.
Case study: The Holderness Coast of East Yorkshire
Grange Farm, Cowden
Easington gas terminal
Effects of the cliff collapse along the Holderness CoastEconomic effectsSocial effectsEnvironmental effectsPolitical effects
Economic effectsSocial effectsEnvironmental effectsPolitical effects Market value of properties has fallen. Houses cant be sold.
Properties cant be insured.
No compensation available so people lose everything.
Loss of land and crops = loss of farmers income People lose homes, may have to move into council houses.
Ill health is rising erosion related stress, sleeplessness and depression Loss of land
Unsightly collapsed buildings
Debris from houses on the beach. Decisions made about which communities are worth protecting.
Cost of sea defences
Protests from angry residentsEffects of the cliff collapse along the Holderness Coast
Describe the costs and benefits of two Soft methods of coastal management. (4)______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Describe the costs and benefits of two Hard methods of coastal management. (4)
Shoreline Management Plans are being produced around the whole coastline of England and Wales to enable coastal engineers to identify long term, sustainable policies for coastal defense. Shoreline Management Plans identify the places that are affected or threatened by flooding or erosion. They state the likely cost of protection work for such areas and test this against the economic value of the land or property.
Managed retreatHard engineeringSoft engineering
Costs and benefits of coastal management
- building artificial structures aimed at controlling natural processes.
Sea Wall very strongbut expensiveCurved wall to deflectthe energy of the wavesback out to sea.
Groyne a timber barrierat right angles to the beach.It traps sediment carried bylongshore drift.Disadvantage wooden groynes will eventually rot.
Rock armour or Rip rap boulders placedat the base of a cliff. Relatively cheap and easy to construct
Timber Revetments slatted wooden barrier which allowswaves to pass through and trap beach material behind .No access to the beach andthey may rot.Gabions wire cages filledwith stones. Cheap but ugly.
- a sustainable approach to managing the coast without using artificial structures.
Beach nourishmentThe addition of sand to an existing beach to make it higher or broader. Attractive, but will wash awayagain. Need groynes to keep it there.
Dune regeneration Marram grass is planted to stabilise sand dunes and help them develop. Walkways protect dunes from damage by trampling
Marsh creationThis involves allowing low lying areas to become flooded by the sea to become salt marshes
Allowing controlled flooding in low-lying coastal areas ORAllowing cliff collapse where the value of the land and property is low.
MappletonSue Earles farm, CowdenWithernsea
Location 1 - MAPPLETON
1. Why were the sea defences necessary? 2. What type of defences were built?3. Were they successful? How do you know?
Examples of HARD ENGINEERINGRock groyneRock armourRock armour
Location 2 - Grange Farm, Cowden (Sue Earles farm!)
Location 2 - Sue Earles farm, Cowden How did the sea defences at Mappleton affect