Transcript Slide 1

What determines whether a particular stretch
of coastline is protected or not?
Whether land is protected or not comes down to
the economic value of the land
Protected
Robin Hood’s Bay
1770-1994, 200 houses went
over the cliffs
Unprotected
Caravans/cheap housing
that is sparsely
distributed
A) Hard engineering
1) Groynes
Mappleton, Yorks.
coast
A) Hard engineering
1) Groynes
£10,000 each (wooden
groynes)
£1.5m each (rock
groynes)
What are they designed to
do?
Stop longshore drift
Further down the coast this
may mean that beaches are
starved of sand and shingle
2) Sea Walls
2) Sea Walls
Expensive at £5,000/m
Designed to stop erosion, but what
landforms would that prevent being
created?
Would you rather go on holiday and see
Old Harry or a sea wall?
This is reduced by
absorbing the energy
and angling the wall
Energy is reflected (not absorbed). Over
time the energy scours the base of the
sea wall undermining it, causing it to
collapse
3) Gabions
3) Gabions
Small rocks, bound in place by cages
absorb the wave energy and reduce
erosion
Much cheaper than sea walls
£1000/m, but do you think they
are attractive?
4) Revetments
4) Revetments
£1,000/m
Open structure of
planks absorb
wave energy, but
allow sand and
shingle to build up
beyond
Are these attractive?
5) Rock Armour and Rip Rap
5) Rock armour or Rip Rap
Relatively cheap
£1,000/m, but
considered
environmentally ugly
When resting on sand and
shingle they may be moved
out of position by waves
Gabions and Groynes
6) Gabions and groynes together
Why might you choose to implement more than one coastal
management strategy at a time?
To protect against erosion and longshore drift
How attractive do you consider
these to be?
B) “Soft” Engineering
Less expensive than hard
strategies
Longer term, more attractive
and sustainable as they work
with natural processes
1) Beach Nourishment
Sand and/or pebbles are brought
in to replace material that has
eroded away. Where do you think
this replacement material has
come from?
It has been dredged from the sea
bed. In some cases it is pumped
onto the shore.
The beach is widened; how
will this affect the energy of
the waves?
It will reduce the energy that
the wave has meaning less
erosion.
Cost: £100/m/yr
2) Stabilising Sand
Dunes
Grasses are planted
in the sand dunes to
bind them together,
holding them in
place.
Footpaths may be
designated. Why might
this be?
To reduce trampling of the
dunes by people, which
erodes them
3) Managed Retreat
When the land by the sea is
of low economic value it may
be allowed to erode.
In some cases this eroded
material forms beaches which
naturally protect the coast.
Holderness case study (landform
case study)
Why protect/manage the coast?: Case
Study Holderness Coast
Locally, rates of erosion have been up to
10-20m with waves biting coast away
Over 30
villages have
been lost since
Roman times,
erosion has
been taking
place for last
6000 yrs
Holderness Coast is fastest
eroding stretch of coastline in
Europe – an average of 2
metres fall into the North Sea
each year
Holderness Coastline Video Answers
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Chalk deposits
Wave cut notch erosion
Boulder clay- left by the ice sheet
The boulder clay is easily eroded as it is a soft rock
Longshore drift
Groynes
RipRap, they stop the waves eroding the coastline by
allowing the wave to break on them and spread out
the energy
Holderness Coastline Video cont’d
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As there is no erosion, down the coastline there will
be no deposits and so more erosion occurs
16m has eroded in 35 years
Sea wall and rip rap. Sue Earl does not live in a
settlement, her farm was deemed as not worth
protecting.
Spit- longshore drift deposition formed it. Groynes
were built to maintain it.
Shifting mudbanks
Too expensive, and there are no important
settlements.
High
energy
waves
because of
long fetch
Chunks of coast
slump down the
cliff
Soft boulder
clay
Thin, narrow
beaches do little to
absorb wave
energy
Why are the beaches thin
and narrow?
Holbeck Hall,
Scarborough
The beaches are thin because the material is
carried away by longshore drift
Holderness Coast – Cliff Processes
Rain water enters cracks
Cracks formed by wetting
and drying
Boulder
Clay Cliff
Material slumps down the cliff
Removal of slumped
material by sea
Slip plane
developing
Sea
Beach
Mappleton and Holderness Coast