Transcript OCR GEOGRAPHY B

OCR GEOGRAPHY B
COASTS
QUESTIONS FOR INVESTIGATION
• How do systems ideas help us to understand
physical processes?
• What processes and factors are responsible
for distinctive coastal landforms?
• Why is the management of coastlines
becoming increasingly important?
Why is the coast called a multi-use
resource?
• Over 4 billion people live in coastal areas and
this number is expected to rise rapidly in the
next 50 years.
• This means it is very important for us to be
able to understand the physical processes and
economic demands which shape this land
Why is the coast called a multi-use
resource?
Coastal areas are a valuable resource for:
• Industrial Development: coasts can offer large areas of
flat land and access to shipping for the import of raw
materials and the export of the finished product
• Transportation: growing industrial globalisation and
trade has meant industrial ports are increasingly
important. Also the growth in cruise holidays has seen
some ports grow
• Recreational Activities: increasing wealth and leisure
time have increased the demand for water sport
activities
Why is the coast called a multi-use
resource?
• Residential Development: coastal areas are seen as
attractive places to live because of the scenery and
the recreational activities they can offer
• Nature Conservation: salt marsh and sand dune
habitats are important environments for rare plant
and animal species
How are coasts shaped by physical
processes?
THE COASTAL SYSTEM
EROSION AND
WEATHERING
TRANSPOTATION
DEPOSITION
How are coasts shaped by physical
processes?
MARINE EROSION
• ABRASION: during heavy storms waves have the energy to
pick up large amounts of sand and pebbles. These are thrown
against the rock and erode the land away
• HYDRAULIC PRESSURE: where the waves break against the
base of the cliff the sheer force of water hitting the cliff
breaks of pieces of rock and erodes the cliff
• ATTRITION: sand particles and pebbles collide against each
other and are broken down into smaller pieces
How are coasts shaped by physical
processes?
COASTAL WEATHERING
• SOLUTION: sea water is corrosive and will slowly dissolve
chalk and limestone. Salt crystals are formed as the water
evaporates, these crystals grow in size causing the rock to
break
• WETTING/DRYING: softer rocks such as clay expand and
contract as they become wet and dry out. This weakens the
rocks and the rock can crumble due to erosion
• MASS MOVEMENT: rock falls, mudslides and landslides are
common features of cliff coastlines because of waves
weakening the base of the cliff and sub-aeriel processes at
the top of the cliff
What landforms are associated with
destructive coastlines?
• As waves approach the shore they pick up
sediment. Breaking waves force water and
sediment up a beach as SWASH when gravity
pulls it back down a beach it is known as
BACKWASH
• Waves which remove sediment from a beach
are called DESTRUCTIVE WAVES because the
remove a lot of material and create a high
level of hydraulic action
How are coasts shaped by physical
processes?
Landforms created by destructive
waves
How does he sea transport material?
The sea transports material it has eroded by a process known
as LONGSHORE DRIFT
How are coastal land forms created
by deposition?
• Waves that deposit sediment are referred to
as CONSTRUCTIVE WAVES because they help
to build up beach material often producing
wide, flat beaches that are important to the
tourism industry
How are coastal land forms created
by deposition?
How are coastal land forms created
by deposition?
THE FORMATION OF SPITS AND BARS
Spits and bars are ridges of sand and shingle that have been
formed by material deposited by breaking waves. They usually
develop where:
• Large amounts of sediment are being moved along the coast
by longshore drift
• There is a sudden change in the direction of the coastline
• The sea is shallow enough to allow the deposited matrial to
reach the surface
How are coastal land forms created
by deposition?
How are coastal land forms created
by deposition?
• Where deposited material joins up two land
areas this landform is called a TOMBOLO
How does the coastline provide a
natural defence against flooding?
• The coastline has always provided an important
buffer zone between the sea and the surrounding
lowlands
• Coastal salt marshes and mangrove forests
provide a natural barrier against storms,
absorbing wave energy and providing a barrier
against high tides
• With rising sea levels Sustainable Management
of coastlines will become increasingly important
How does removing coastal wetlands
increase the risk of flooding?
• In many areas of the UK salt marshes have
been drained for farming or development
• This drained land is then protected by a sea
wall. At high tide the sea will often reach the
sea wall and may eventually collapse
• In extreme cases this has been blamed for
increasing the impact of many natural
disasters such as the 2004 Thailand tsunamis
How can coastal areas be protected?
• Hard engineering: controls the sea by building
barriers between the sea and the land, or forces
the wave to break before it reaches the land
• Soft engineering: works with the natural
environment by protecting the beach so the
beach can absorb the waves energy before it
reaches the land
• Managed retreat: involves allowing the sea to
flood inland until it reaches higher land, where
the natural shape of the land will prevent any
further flooding
How can coastal areas be protected?
REVETMENTS
Sloping ramps that face the sea and absorb
the waves energy
How can coastal areas be protected?
RIP-RAP (ROCK ARMOUR)
Large boulders piled up in front of cliffs or sea
walls
How can coastal areas be protected?
SEA WALL
A concrete barrier that protects areas from wave
attack and flooding. The curve deflects the energy
How can coastal areas be protected?
GABIONS
Wire cages filled with rocks and stacked to
form a barrier against the waves
How can coastal areas be protected?
OFF-SHORE BREAKWATER (REEF)
Rock structures are built parallel to the coast and
force the wave to break before it reaches the land
How can coastal areas be protected?
GROYNES
Wooden or concrete barriers built at right angles to the
beach. They both absorb the waves energy and rap sediment
behind them to maintain the beach
Case Studies
• Blakeney Point, Norfolk: natural sea defences
• Pevensey Bay, East Sussex: sustainable coastal
management
• Cuckmere Estuary, East Sussex: coastal flood
protection