Zusammenfassung der Ressource
COASTS
- Erosion
- Weathering
- Freeze thaw - water
gets in cracks and
freezes, expanding the
crack
- The breaking down
of man made
things by weather
- Mass Movement
- The downhill movement of
material under the
influence of gravity
- Impacting factors:
- Undercutting the cliff
- Building on the cliff
top increases the
weight
- Rain saturates the
rock which
increases the
weight
- Weaker rocks (eg. clay)
are more likely to
collapse than srong rocks
(eg. granite)
- Coastal erosion
- Hydraulic action - waves
trap air in rock forcing it
apart
- Abrasion - rocks
thrown at cliff face
by waves scraping
it away
- Attrition - rocks
bump into each
other and get
smaller
- Solution - sea
water
dissolves the
rocks
- Erosional landforms
- Headlands and bays
- Soft rock (eg.
clay) erodes
quickly to make bays
- Swanage bay - Dorset
- Hard rocks (eg.
limestone) erodes
slowly to make
headlands
- The Foreland - Dorset
- Caves, arches, stacks and stumps
- 1. A crack in the
headland is expanded
by hydraulic action
- 2. The crack
becomes a
cave
- 3. The cave is opened
up to form an arch
- Durdle door - Dorset
- 4. The top of the
arch collapses to
form a stack
- Old Harry -Dorset
- 5. The stack
is eroded to
form a
stump
- Old Harry's wife - Dorset
- Wave cut notches and platforms
- Waves undercut a cliff to
leave an overhanging
platform above a wave
cut notch.
- The platform
eventually collapses
and the process
happens again
- Transportation
- Transportation of different rocks
- Traction - big rocks
roll along the sea
bed
- Saltation - pebbles
bounce along the
sea bed
- Suspension - sediment is
small enough to be
carried along by the
water
- Solution - tiny
particles dissolve in
the water and move
with it
- Longshore drift
- Direction depends on
the prevailing wind
- Constructive waves have
a strong swash
- Destructive waves have a
strong backwash
- Sediment is moved along the
shore by a diagonal swash
and a straight backwash
- Swash - a wave moving inland
- Backwash - a wave
moving back towards
the sea
- Beaches
- Sand beaches
- Formed by constructive waves
- Can have sand dunes
- Shallow gradient, almost flat
- Pebble beaches
- Formed by destructive waves
- Steep gradient, often has berms
- Large pebbles at the
back of the beach
- Depositional landforms
- Spit
- A finger of sand formed by longshore drift
- Hook
- A spit with a marsh behind it curves
due to the low energy of the marsh
to create a hook
- Bar
- A spit grows between headlands to create a bar
- Sand dunes
- 1. Embryo dune
- Small dune closest to the water
- Plant found: Couch grass
- 2. Fore dune/yellow dune
- Plant found: Marram grass
- 3. Grey dune
- Plant found: Willow
- 4. Dune slack
- A big dip between high
dunes where water can
get trapped
- Plant found: Common sallow
- 5. Mature dune
- Big dune furthest
from the water
- Plant found: Pine
- Coastal management
- Hard engineering -
building defenses
- Sea wall
- Absorbs energy from waves
and can redirect them (if
curved at the top)
- Advantage: Strong
and effective
- Disadvantage: Expensive
- £6000 per meter
- Rip rap
- Absorbs energy from waves
- Advantage: Simple
to maintain
- Disadvantage: Expensive -
£1000 per meter, can look
messy, can be dangerous
- Groynes
- Traps sediment from
longshore drift and absorbs
energy from waves
- Advantage: Helps to build
up a natural defence
- Disadvantage: Expensive - £10000
- Soft engineering - in
line with the natural
environment
- Cliff regrading
- Makes a cliff less steep
- Advantage: Cheap
- Disadvantage: Loss of
some cliff
- Dune stabalisation
- Planting marram grass to
hold dunes together
- Advantage: Cheap,
sustainable, looks natural
- Disadvantage: Doesn't
always work
- Managed retreat
- Allowing an area to become flooded
by removing costal protection
- Aims
- Improve costal stability
- Protect areas further inland
- Rely on natural defences
- Creates saltmarsh - a low energy
environment
- Northen Island,
Essex - River
Blackwater flooded
in 1991, 8000sq
metres, nature
reserve
- Advantages
- Earth banks develop
- Maintinence
costs are low
- Saltmarsh and
vegitation provide
protection from
storms
- Beaches can
naturally
replenish
- Disadvantages
- Land will be lost
- Settlements will
be destroyed
- Not socially acceptable
and compensasion will
be needed for land
owners
- Schemes are
unpredictable
- Case study
- Minehead
- A coastal town on the Bristol
channel and the north-west
coast of Somerset
- Coastal management
strategies used
- A 0.6m high
seawall with a
curve to
deflect waves
- Expensive but the
walkway build
beside it is popular
with tourists
- Rock armour
- Expensive but low
maintenance and
asthentically
pleasing
- Wildlife can
benefit by
creating new
habitats in it
- More sand put on
the beach (beach
nourishment)
- Forces waves
to break
further out to
sea
- Attracts tourists
- Four rock groynes
- Helps to stop sand
movement from
longshore drift
- Provides wind
shelter for
tourists
- Can increas
erosion further
down the coast