Transcript TOPIC COASTLINES

TOPIC
COASTLINES
Local Geology
The coastline of the
British Isles is not
smooth.
Why ?
The nature of the
rocks is important.
Some are very hard
but some are very
soft and are eroded
easily.
Wave Action
Destructive Waves
Winds generate waves. Strong winds build powerful waves with lots
of energy. Gentle winds produce gentle waves with low energy.
Destructive waves have a very strong backwash and a weak
swash.
They remove beach material.
Constructive Waves.
These waves deposit material at the coast. They build up the coastline. The
strong swash pushes sand / shingle up the beach.
Features / Landforms produced
by EROSION.
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What are the processes of EROSION ?
CORRASION
ATTRITION
SOLUTION
HYDRAULIC ACTION.
Jurassic Coast Dorset
Bays and Headlands
Cardigan Bay: Wales
1.Describe what has happened in these sketches.
2.Explain what has happened in these sketches.
DURDLE DOOR in DORSET
What will be formed when the arch collapses?
Headland Erosion.
OLD HARRY ROCKS
The headland itself is eventually broken down by erosion.
Remember the sequence of events :
CAVES ARCHES STACKS + STUMPS
Case study / Example
OLD HARRY ROCKS
in
Dorset
Cliffs and wave cut platforms
These are the Severn Sisters
On the south coast between
Brighton / Eastbourne.
Look for the point where the cliff line
used to be.
Notice the cliff line today.
A great example of a wave cut
platform!
What is Longshore Drift ?
Waves approach at an angle. Material is moved along the beach.
Is longshore drift a good thing / bad thing ? Why ?
Spit Formation
Key Terms : EROSION-----------TRANSPORTATION ---------DEPOSITION
Draw arrows to label the places on the sketch.
Spit animation
Watch how material is
transported along the
coastline by longshore
drift. The coastline
changes direction and
the material is moved
out to sea and
deposited.
Case study : Spurn
Head
Longshore Drift also creates….
SPITS
This is Spurn Head the
largest spit in the British
Isles.
What features are produced as a
result of Longshore Drift ?
The sand has moved along the coastline and formed a BAR. A bank of sand
across the estuary.
Why is Longshore Drift a problem?
Longshore drift moves
material along the coast.
Places can be left with no
sand / shingle to protect the
coastline.
The waves can easily
attack / erode the cliffs.
Case study of Holderness
Where is the Holderness Coast?
Holderness Coast
In this photograph you can see that the beach is narrow and the cliff is
open to attack from the waves. The house on the cliff top is under
threat of collapse into the sea.
Now watch some film clips of the
Holderness Coast to see the
effects of interfering with the
natural process of Longshore Drift.
Coastal Management
What are Groynes ?
• Longshore Drift moves material along the
coastline leaving some parts unprotected.
• How can we stop Longshore Drift ?
Wooden Groynes trap beach
material
Examples of Groynes
Look at how the waves
approach at an angle to the
shoreline.
Note how material builds up
on unevenly between the
groynes.
Are Groynes a good or bad thing?
• Good Points :
• Groynes Trap material and it
builds ups protecting the coast.
• Case study
• Bournemouth Beach.
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What has happened in this
photograph ?
Bad Points
The natural movement of material is
stopped and other places along the
coast do not get the sand / shingle to
protect the coastline.
Case study Holdermess
Coastal Protection
• Some parts of our
coastline are protected
from erosion. Why?
• To protect towns that
have large populations
and whose local economy
depends on tourism or
fishing or industry.
Coastal Protection
Coastal Protection
Gabions are rocks held together with
Wire netting. They stabilise cliffs.
Rock Armour and curved sea
wall.
Coastal Protection
Rip Rap wooden barriers
hold rocks together
Look at this sketch to see what
defences have been built on Brighton
Seafront.
What is Managed Retreat?
It can cost millions of
pounds to build sea
defences.
Low value land is not
worth protecting.
Nature is allowed to take
its natural course.
Birling Gap near
Eastbourne in Sussex
Will not receive any
money for coastal
protection.
This low value
farmland will be
allowed to flood.
Case study of Bournemouth
• Bournemouth Seafront is heavily defended.
• Wide sand / shingle beach.Wide Promenade / Concrete sea wall.
Gabions. Grass banks stabilise the soil.
Bournemouth Facts.
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Population 163.000
1.5 million visitors a year.
Tourists spend over £130million a year.
7000 jobs in tourists sector.
Bournemouth has: 7 miles of golden
sands.
• Bournemouth receives 7.7 hours of
sunshine on average every day.