Transcript Coastal Landscapes Revision

Q1: Coastal Landscapes
15 marks
Coastal Processes Produce Landforms
Types of Waves
Weathering
Rocks are broken down where they are and do not get moved.
Physical weathering
Freeze-Thaw
Biological weathering
Seeds fall into cracks of
rocks. Seed grows and
as roots grow they force
rocks apart .
Chemical weathering
Carbonation
CO2 is absorbed by H2O to create
carbonic acid (H2CO2)
Erosion
Rocks are broken down and carried away by something - such as the sea
Mass Movement
Material shifts down a slope under the force of gravity.
• Rocks and loose material shift down a slope - e.g. a cliff
• Mass movements cause coasts to retreat more rapidly
Soil Creep
• Slowest downhill movement
• Gravity pulls water in the soil downhill
• Soil particles move with the water
• Heavy rainfall will speed up movement
• Slope appears to have ripples
• Ripples are known at ‘terracettes’.
Slumping
• Large area of land moves down a slope
• Common on clay cliffs
• Dry weather makes rock contract & crack
• When it rains, water gets into cracks
• Soil becomes saturated
• Large piece of rock is pulled down the cliff
Landforms created by coastal erosion:
Cliffs & Wave-Cut Platforms
Landforms created by coastal erosion:
Headlands & Bays
Landforms created by coastal erosion:
Cave, arch, stack & stump
Landforms created by coastal deposition:
Longshore Drift
Landforms created by coastal deposition:
Beaches
Beaches are formed by deposition between the high water and low
water marks. They are formed by constructive waves.
Landforms created by coastal deposition:
Spits
Landforms created by coastal deposition:
Bars
Coastal Landforms are subject to
change
What affects the rate of coastal erosion?
Fetch
How far the wave has
travelled. The longer the
fetch, the stronger the
waves.
Geology
Softer rocks will erode
more quickly. However,
harder rocks sticking out at
headlands will also be
vulnerable to the full force
of the waves’ power
Defence
If the coast is defended it will
slow down rates of erosion.
However, groynes will speed up
erosion further down the coast
if it is not defended.
The effects of coastal recession on people and the environment
Happisburgh
25 properties & lifeboat
launch station lost since
1995. Grade 1 listed
church estimated to be
lost to the sea by 2020.
Westward Ho!
Coastal golf courses are at
high risk. The Royal North
Devon Golf Club at
Westward Ho! Is losing its
7th & 8th holes.
Walton on the Naze
Present rates of erosion of 1.5m
per year means the tower will
be lost to the sea. The area
around the tower is used for
recreation & is not worth
spending money to defend it.
Barton on Sea
Exeter to Penzance Railway
The sea often washes over the tracks. Once Since 1975 the seaside café & Manor Lodge had to
be demolished as they became dangerously close
160 passengers were stranded for 4 hours
to the sea. In 2004 the coastal footpath was closed
because the sea made the electrics fail.
& re-sited further back from the cliff edge.
Predicting and preventing the effects of coastal flooding:
Forecasting
The Met Office predicts the likelihood of
a flood. This is communicated through
weather forecasts and news on TV, radio,
websites and apps.
The Environment Agency monitors sea
conditions 24/7. The Storm Tide
Forecasting Service provides coastal
flooding info on a 24 hour flood hotline
and on their website.
Predicting and preventing the effects of coastal flooding:
Building Design
In Bangladesh all 1 & 2
storey buildings must
have an external staircase
to the roof.
Houses along the coast at
Malibu in California are
built on stilts to protect
them from storm tides.
Properties built in areas
of flood risk have designs
to protect them from the
wind, rain and storms.
Predicting and preventing the effects of coastal flooding:
Planning
Planning permission may The Thames Flood Barrier was In Bangladesh the Coastal
not be granted if the land completed in 1982. In 2010 the Embankment project has
is at risk from or has a
Environment Agency installed
led to the building of 12
history of flooding.
new flood walls along the river
sea-facing flood walls &
along with other flood defences
500 flood shelters.
to protect London against future
flooding.
Predicting and preventing the effects of coastal flooding:
Education
Governments give advice In Bangladesh many coastal In King’s Lynn, Norfolk, there
to the public via websites
areas have flood warning
is a flood siren. The council
about how to protect
systems.
employs officers to visit
homes and what to do if a
homes to warn people &
flood occurs.
help them prepare if flooding
is forecast.
Hard Engineering
Major construction work that aims to prevent floods & usually not great to look at!
Revetments
Rip Rap
Recurved Seawalls
Slatted wooden structures
at the base of a cliff
 Absorb wave energy
through slats
 Effective for many years
 Relatively cheap
 Not effective in storms
 Regular maintenance
 Makes beach
inaccessible for tourists
Usually concrete wall,
Large rocks placed in front
modern ones have a curve
of the cliff
 Breaks up wave energy  Reflect & absorb wave
energy
 Effective for many years
 Effective for many years
 Cheap
 Visible & therefore
 Not effective in storms
makes people feel safe
 Unattractive
 Very expensive
 Makes beach
 Unattractive
inaccessible for tourists
Hard Engineering
Groynes
Usually wooden structures
stretch from the coastline
in right-angles out into sea
 Prevent longshore drift
 Keeps beach in place for
tourist industry
 Effective for many years
 Starves beaches further
down the coast of
sediment > speeds up
erosion elsewhere
 Unattractive
Gabions
Wire cages filled with
stones
 Rock cages breaks up
wave energy
 Relatively cheap
 Not as effective as other
methods
 Wire cages can break –
need to be well secured
Offshore Reefs
Concrete blocks/natural
boulders sunk offshore
 Waves break further
offshore > reduces
their power to erode
 Less wave energy will
allow more sand to
build up on beach
 Difficult to install
 Storms may remove
them
Soft Engineering
Work with natural processes aiming to reduce effects of floods – tend to blend in well
Beach Replenishment
Cliff Regrading
Managed Retreat
Adding sand/pebbles to the Cliff cut back with new gentle Allow nature to take its
beach
slope = reduce slumping course & flooding to occur
 Looks natural & is cheap
 Cheap
 Covered in netting to
 Keeps beach in place for
encourage vegetation  Creates wetland habitats
tourist industry
for plants & birds
 Natural habitat >
 Beach = natural defence
 Some people will lose
encourages wildlife
 Requires constant
their land
 Not as effective as other
maintenance
 Difficult to estimate how
methods
 Noisy & heavy machinery  Homes on cliff may need
much land will be lost –
will disrupt homes &
especially in face of
to be demolished to allow
businesses
rising sea levels
work to take place
 Affects plant & marine life
Coastal Management
Managing the coast: Walton-on-the-Naze, Essex
1977: Groyne, Cliff & Seawall Heaven!
• Groynes built to stop longshore drift moving sediment from the south to the north
• Cliff regraded and drainage channels installed to make cliffs stable
• Slopes planted with gorse & nettles to stop people climbing on the cliffs
• Seawall built to protect the bottom of the cliffs as they are made up of soft clay
1998: Rip-Rap’s Looking Great!
Rip-Rap placed along the bottom of the cliffs. 300 tonnes of Leicester granite placed
around the Tower Breakwater
1999: Beach Replenishment’s Mighty Fine!
Beach replenished with sand & gravel from Harwich Harbour
Alternative case studies: Happisburgh, Norfolk or Barton on Sea, Hampshire