Things you should know off Things you should know off by heart!by heart!

When I saw off by heart I mean anything that’s written in this

PowerPoint you should be able to write in your exam!!

Constructive and Destructive Constructive and Destructive WavesWaves

• At least two differences between constructive and destructive waves e.g.– Constructive waves are long, low waves that

build up the beach.– Destructive waves are much more frequent

waves with a shorter wave length and erode the beach.

Erosion

• Hydraulic action – air gets forced into cracks and then pops like air from a champagne bottle

• Abrasion – rocks hit the cliff

• Attrition – rocks hit other rocks wearing each other away

• Corrosion – sea water dissolves the rock

Mass MovementMass Movement• Bottom of the cliff eroded by waves and undercut

• Rainfall saturates cliff and makes it heavier

•Rocks slide down cliff

•Often happens in clay

• Rocks are weathered on the cliff face

• They break loose and fall under the influence of gravity

Wave Cut Platforms

• Hydraulic action erodes the coastline causing undercutting.

• Rocks above the notch are unsupported and collapse.

• The rocks from the cliff are eroded by abrasion and attrition causing a wave cut platform.

• The cliff retreats inland

Rate of cliff recession

• The longer the fetch, the further the wave has to travel. It picks up more energy and so erodes the cliff quicker

• The softer the geology (rock) the easier it is to erode so cliff recession happens more quickly

Cave, arch, stack, stumpCave, arch, stack, stump

Longshore DriftLongshore Drift

• The direction of the wind forces waves onto the beach at an angle

• Swash carries sediment (sand and rocks) up the cliff

• Backwash pulls material off the beach under gravity.

• Sediment is transported along the coast

Formation of a spitFormation of a spit

• Longshore drift carries material along the coastline

• When the coastline changes direction, longshore drift continues and extends the beach into open water

• The end of the spit often becomes curved because of changes in the wind direction

• Sediment often builds up in the sheltered water behind the spit to form a salt marsh

Effects of coastal recession

Human• Loss of land• Loss of property and belongings• Insurance has to pay out a lot of money

Environmental• Loss of habitat for animals• Loss of breeding grounds for birds

Coastal Flooding and Protection

Thames Barrier build to protect the city of London. Barriers closed during bad

weather and high tide to protect peoples businesses and property.

People in Bangladesh plan for flooding by building their houses on stilts. This

protects their houses and belongings.

Met office predicts heavy rain. People can ring Floodline to see if their property is at risk. Can then protect property with sand

bags, evacuating or moving belongings upstairs.

Hard EngineeringHard Engineering

• Groynes – stop longshore drift

• Revetments – protect the cliff and capture sediment

• Seawall – protects the cliff

• Riprap – absorbs wave energy and protects the cliff

• Offshore reefs – absorb wave energy to allow a wide beach to develop.

Soft EngineeringSoft Engineering

• Beach replenishment – taking sand from the bottom of the ocean and putting it back on the beach

• Managed retreat – coastal erosion is allowed to happen

• Cliff regrading – making the cliff face longer and less steep to stop slumping.

Coastal Protection - You should know at least 2

advantages and 2 disadvantages for hard and soft Hard EngineeringHard Engineering

Advantages

(1) protects the land and buildings behind the cliff.

(2) absorb wave energy and stop material from the beach being eroded.

Disadvantages

(1) Very expensive to build and maintain

(2) They often look ugly

Soft EngineeringSoft Engineering

Advantages

(1) Looks completely natural

(2) Managed retreat and cliff regrading are much cheaper

Disadvantages

(1) Erosion will continue to happen

(2) They have be to replaced much more often

SwanageSwanage

Swanage is build on clay which is susceptible to erosion. To protect Swanage:

• A seawall was built as a barrier to wave attack• The cliff was regraded to prevent slumping• A series of groynes were installed to reduce

longshore drift.• 90000m3 of sand was pumped onto the beach.