Coastal management
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Coastal defence
(management) against
flooding and erosion.
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What are the main types of soft
and hard engineering used on the
coastline of the UK?
(Coastal defences)
Advantages and disadvantages of
these techniques
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Definitions
• Soft engineering: method of coastal
management which works with natural
processes at work on the coastline and to be
unobstructive (unnoticeable) visually. It does
not involve major construction.
• Hard engineering: method of coastal
management which involves major
construction work.
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Hard engineering
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Rip-rap
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Recurved sea wall
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Groynes
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Gabions
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Offshore reef
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Revetments
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Soft engineering
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Beach replenishment
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Cliff regrading
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Case Study
• Describe how the coast is
managed in a named location.
• Consider the costs and benefits of
different approaches to protecting
the coast in a named location.
Swanage
In Dorset on the south coast of England
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Chalk
Clay
RATES OF EROSION
ESTIMATED ABOUT
40-50 CM PER YEAR
Limestone
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Location of examples
Swanage Bay
Peveril Point
Durlston Bay
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In Durlston Bay, erosion mainly occurs at one particular point,
where there was a major weakness in the resistant limestone
rock. There were three methods used to protect the cliffs from
erosion (recession):
Cliff regrading – extending it
forward, making slope longer
and less steep. Reduces the risk
of mass movement.
Drainage – removing excess
water, so slope wasn’t as heavy
or lubricated after rain. Reduces
the risk of mass movement and
freeze-thaw weathering.
Rip rap placement – Large boulders
at the base of the cliff to resist
wave attack and dissipate wave
energy.
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Swanage Bay
This is a popular recreational area for beach users,
diving, fishing and sailing.
Erosion occurred along a considerable length of
cliff.
The town has been developed on soft eroding cliffs
and annual falls & slips have left some properties,
such as The Pines Hotel, very close to the cliff top.
Swanage landslide caught on camera
Coastal management issues:
The potential impact of any coastal defence works
on Swanage's tourism and the aesthetic and
landscape quality of the coastline.
Photo Gallery
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SEA WALL
• Built in the 1920s and provided a promenade
as well as a barrier to wave attack.
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The most cost effective
method was found to be
the replacement of the
1930s groynes and
replenishment of the
beach sediment.
Groynes
A series of mainly timber groynes were installed in the 1930s, and
eighteen of them have been replaced in 2005 with new ones.
These reduced longshore drift and help make sure that a beach
remained in place to absorb the energy of breaking waves.
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Beach replenishment
In November of 2005, 90,000 m3 of sand was
deposited on the beach. The beach will need to
be recharged with around 40,000m3 of sand
every 20 years.
This works with the groynes to ensure a good
size beach.
The works were finally completed in June 2006
at an estimated cost of £2.2 million.
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Cliff regrading
• A series of steps were made in the cliff to
reduce slope angles
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However: January 1st, 2013
Dorset Coastguard have restricted access to
Swanage beach and the South West Coastal
Paths, after heavy rains over the holiday period
caused further mudslides and cliff subsidence in
Swanage.
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What are the effects of coastal
recession on people and the
environment?
Coastal recession (when the coast
is eroded and retreats)
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The effects of coastal recession
on people and the environment
Amount of effect is determined by the land use.
Use for settlement>farmland
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Explain the effects of coastal recession on
people and the environment. Use examples in
your answer. (6)
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North Norfolk coast
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Managed retreat/Hold the line
policies?
Managed retreat is an alternative to
constructing or maintaining coastal structures.
Managed retreat allows an area to become
flooded.
Hold the (existing defence) line – to build or
maintain artificial defences so that the position
of the shoreline remains. Use of hard and soft
engineering
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Cliff recession along the North
Norfolk coast
Why has The North Norfolk coast’s new Shoreline
management Plan adapted a managed retreat rather
than ‘hold the line’ policy?
Erosion has always been a problem on the Norfolk
coast because of its soft rock geology and its long fetch
(Destructive/high energy waves)High rate of erosion.
Erosion rates are between one and three metres per
year, so it has become increasingly difficult and
expensive to continue protecting certain locations and trying to do so makes erosion worse in other areas
along the coast. This will get worse as the effects of
climate change increase.
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Predicted impacts on people
What will be lost to the sea over the next 100
years?
- Nearly 1000 homes
- 1400 caravan and chalet parks
- Six hotels and guest houses
- Seven historic buildings
- 3.5 km of road
- Seven golf course holes
- Three community halls
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Happisburg (North Norfolk coast)
Village of Happisburg (population= 850)
Factors which explain high rates of erosion in this
area:
Geology: Cliff made of soft rock (clay, gravel and
sand deposited by glaciers)
No sea defences: 1958: use of revetments to
reduce coastal erosion. From 1995 no repairing of
coastal defences high rates of erosion.
Government has refused to protect the village
because it is not cost effective: the village is less
valuable than the cost of the defences to protect it.
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Coastal recession at Happisburg
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Watch!
Living with coastal erosion in Happisburgh, East
Anglia (1)
Living with coastal erosion in Happisburgh, East
Anglia(2)
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Coastal recession along Beach Road
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4 impacts on people
Loss of homes
Since 1995: 25 properties and the village’s lifeboat
launching station washed away.
Loss of value
Houses worth £80,000 when the coast was
defended, are now valued at 1£.
No insurance of property against coastal erosion
Erosion-related stress and depression
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2 impacts on the environment
• Loss of land:
At Durlston Bay near Swanage the cliff receded 12
metres between 1968 and 1988. In 200/01 severe
storms and high energy waves led to a further
retreat of another 12 metres.
• Loss of natural habitats
Durlston County Park also lies on the top and is
home to over 250 species of birds that nest on the
cliff. These habitats are threatened by cliff
recession, which can affect the breeding of rare
species such as puffins and falcons.
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Coastal flooding occurs when normally dry, low-lying land
is flooded by sea water
Causes of coastal flooding
How are the effects of coastal
flooding reduced by prediction
and prevention?
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Causes of coastal flooding
• Severe weather: Strong winds and storms which
can increase the height of waves and tides.
• Storm surge: A storm surge is an offshore rise of
water associated with a low pressure weather
system*, typically tropical cyclones. Storm surges
are caused by high winds pushing on the ocean's
surface. The wind causes the water to pile up
higher than the ordinary sea level.
*A low-pressure area, low or depression, is a
region where the atmospheric pressure is lower
than that of surrounding locations
• Sea level rise
Coastal flooding associated with sea level rise will
become a significant issue into the next 100 years.
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Storm Surge
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How are the effects of coastal
flooding reduced by prediction and
prevention?
This should be studied through forecasting,
building design, planning and education
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Forecasting
UK (HIC): The Met Office predicts (forecasts) the likelihood of a
flood. The information gets to householders through weather
forecasts and news broadcasts on the TV and radio. It is also on
their website.
The Environment Agency monitors sea conditions 24 hours a day,
365 days a year. Forecasts of coastal flooding are provided on a 24hour Flood hotline.
Bangladesh (LIC): The Meteorological Department has three radar
stations that transmit weather updates.
The Bangladesh Disaster Bureau also issues cyclone alerts through
the national media as soon as a cyclone is detected by satellites.
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Coastal flooding can be predicted. Justify this
statement. (3)
As well as the monitoring which is being done by
the Met Office, the Environment Agency also
monitors sea conditions over a 24 hour period, 365
days a year. The Storm Tide Forecasting Service
provides the Environment Agency with forecasts of
coastal flooding which the Environment Agency
communicates to the public via their website or
phone line
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Describe how building design can reduce the effects of
coastal flooding. Use examples in your answer. (4)
Building design – homes on stilts, waterproofing measures
Planning – land use zoning; allow reference to defence if
linked to planning, evacuation (e.g. monitoring by
Environment Agency). Allow forecasting as part of
planning. E.g. In LICs coastal homes in areas prone to
flooding are designed with stilts (1). Therefore when
flooding occurs possessions are not destroyed as the water
is able to pass below the home (1).
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Planning
UK: Before building takes place a full check must be
made to ensure that the area is not prone to
flooding. Planning permission will not be granted if
it is.
The Thames Flood Barrier was completed in 1982.
However, new flood walls along the river and many
other flood defence techniques will be installed to
protect the London area against flooding.
(See photo of the Thames Flood Barrier on blog)
Bangladesh: The Coastal Embankment project has
led to the building of 12 sea-facing flood walls and
500 flood shelters.
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The Thames Flood Barrier
The Thames Barrier is one of the worlds largest flood barriers and
serves to protect London from flooding during exceptionally high
tides and storm surges.The Barrier can be lifted at high tide to
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prevent sea waters flooding London
Flood shelters
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Explain how education can reduce the effects of coastal flooding.
Use examples in your answer. (4)
Education
UK: The government gives advice to the public via its website.
There is general advice on how to protect their homes from
flooding and what to do if a flood occurs.
UK: Environmental Agency page: Prepare your property for
flooding.
Bangladesh is integrating education about disaster preparedness
into school curricula for grades three through ten. Schools practice
safety programs and drills nationwide in March and October.
The country has already had an effective warning system for more
than four decades.
In 2007 Cyclone Sidr struck Bangladesh and killed about 3,000
people. It was estimated that the cyclone warning system helped
saved 100,000 lives.
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