Transcript Holderness Coastline

Holderness Coastline
Aims and objectives
• To understand that coastlines work as a
system and are dynamic.
• To understand the processes of coastal
erosion and how these shape the
Holderness Coastline.
• To discover how the coastline is being
protected.
• To gain in depth knowledge of the
Holderness Coastline, looking at
Flamborough Head, Hornsea, Mappleton
and Spurn Point.
• To start and complete a geographical
enquiry into the Holderness Coastline.
Location : Holderness
Coastline
The Holderness Coastline is located on the
North East coast of England.
Erosion of the Holderness
Coastline
There are three main processes at work along any
stretch of coastline. These are :
EROSION
TRANSPORTATION
DEPOSITION
Erosion is occurring at a rapid rate along the
Holderness Coastline and this is creating many
problems.
Focus areas along the
Holderness Coastline
• The Holderness Coastline of the East Riding of
Yorkshire is suffering from the worst coastal
erosion in Europe. In the last 2000 years the
coastline has retreated by almost 400m and
since Roman times over 30 villages have
disappeared into the sea between Bridlington
(just south of Flamborough Head) and Spurn
Head.
• Although large towns such as Hornsea are
protected by sea walls they may eventually be
left cut off at the end of a long peninsula.
• About a million years ago the Yorkshire
coastline was a line of chalk cliffs almost 32km
west of where it now is. During the Ice Age
deposits of soft boulder clay (or till) were built
up against these cliffs to form the new
coastline. It is this soft sand and clay which is
easily eroded by the action of waves.
What is erosion ?
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Erosion is the process by which coastline rocks are broken up by
the action of the sea and transported out to sea or along the coast
by waves and the wind.
As the wave approaches shallow water near to the coast, its base is
slowed down by friction against the sea bed. The top of the wave
will move faster, increasing in height and eventually breaking onto
the beach. If it has a strong backwash it will drag large amounts of
material down the beach.
The Holderness coastline is eroding at a rate of 1-3 metres per
year.
Coastal erosion can take a number of forms:
• Seawater can compress air into cracks in rocks. When the air
escapes it does so under pressure and shatters the rock
(hydraulic action)
• Large waves throw beach material against the cliffs - a process
known as corrasion.
• In a process known as attrition waves cause rocks and pebbles
to crash into each other, causing them to break up.
• Certain types of coastal material, such as chalk are slowly
corroded by acids dissolved in the sea water.
How do waves erode the
Holderness Coastline ?
Waves breaking at the rate
of 10 per minute or less are
building up beach deposits.
Waves breaking at a rate of
10 or more (especially 15) are
removing sand and pebbles
from the beach.
Constructive waves have a strong swash
Destructive waves have a weak swash
(movement up the beach) and a weak
backwash (movement back down the beach).
(movement up the beach) and a strong
backwash (movement back down the beach).
The Holderness coast is subject to the full force of the waves from the
north sea with minimal loss of energy before they reach the cliffline.
Journey along the
Holderness Coastline (from
north to south)
This lesson we will take a journey along
the Holderness coast from Flamborough
Head, stopping at Hornsea, Mappleton
and ending at Spurn Point.
Along the way we will be looking at
coastal features, defences, processes
and the impact the sea has on the
people that live there.
Holderness journey fact
file
The Holderness Coast is one of Europe's fastest eroding coastlines.
The average annual rate of erosion is around 2 metres per year.
The main reason for this is because the bedrock is made up of till.
This material was deposited by glaciers over 18,000 years ago.
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The Holderness Coast is a great case study to use when examining
coastal processes and the features associated with them. The area
contains 'text book' examples of coastal erosion and deposition.
The chalk of Flamborough provides examples of erosion, features
such as caves, arches and stacks.
The soft boulder clay underlying Hornsea provides clear evidence
of the erosional power of the sea.
Mappleton is an excellent case study of an attempt at coastal
management.
Spurn Point provides evidence of longshore drift on the Holderness
Coast. It is an excellent example of a spit.
Geology at
Flamborough Head
The most striking aspect of
Flamborough Head are the white
chalk cliffs that surround it. The
chalk lies in distinct horizontal
layers, formed from the remains
of tiny sea creatures millions of
years ago. Above the chalk at
the top of the cliffs is a layer of
till (glacial deposits) left behind
by glaciers 18,000 years ago,
during the last Ice Age. As the
cliffs below are worn away by
the action of the waves, the clay
soil often falls into the sea in
huge landslips.
Structure of Chalk
Flamborough Head
Joint
Bedding
plane /
fault line
The sea attacks the coast
around the headland in two
ways. Waves beat against the
vertical cliffs and, at the high
water line, weak points in the
chalk are worn away into caves.
The weakest points are where
vertical cracks or fault lines
have appeared in the horizontal
beds of chalk. At places on the
cliffs where the chalk juts out,
these caves are worn away into
rock arches. If the top of an
arch collapses, the result is a
pillar of chalk cut off from the
rest of the headland - this is
called a stack. Flamborough
Head has many caves and
arches, as well as a few stacks.
The process of erosion that has
created them can take hundreds
of years to do its work.
Flamborough Head
Coastal features
Erosion of a Headland
Caves
Arch
Stack
Hornsea
• Location
• A 2.9km stretch of shoreline fronting
the town of Hornsea. A high density
urban development containing
residential and various tourist related
properties, Hornsea's local economy is
dependent on tourism and recreation
as well as incorporating a small fishing
industry.
• Geology
• Hornsea lies upon unconsolidated till.
This material was deposited by
glaciers during the last ice age 18,000
years ago.
• Coastal Features
• The groynes on Hornsea beach ensure
wide and relatively steep beaches.
The beach material is made up of sand
and shingle.
Hornsea
Coastal Management
The position of the coastline at Hornsea has been artificially fixed
since existing coastal defences were erected in the early 1900s.
Hard defences in the form of a concrete seawall and timber groynes
afford protection and an on going refurbishment programme ensure
this has continued. More recently a stone gabion has been erected
to the south of Hornsea. This helps protect the caravan park. Beach
material is being transported south along the Holderness Coast by
longshore drift. In Hornsea sand has accumulated where protection
exists. This is because the groynes provide a barrier to sediment
transportation. This has reduced erosion within the section but
increased rates are evident further south.
Hornsea’s Coastal defences
Wooden groyne –
notice the
difference in
sand heights.
Wooden groynes and
rock wall.
Gabions.
Concrete sea wall,
protects the caravan park.
Mappleton
• Location
• Situated approximately 3km south of
Hornsea lies the village of
Mappleton. Supporting approximately
50 properties, the village has been
subject to intense erosion at a rate
of 2.0m per year, resulting in the
access road being only 50m from the
cliff edge at its closest point.
• Geology
• Mappleton lies upon unconsolidated
till. This material was deposited by
glaciers during the last ice age
18,000 years ago.
• Coastal Features
• The two rock groynes at Mappleton
have helped develop wide and steep
sandy beaches.
Why protect Mappleton ?
In 1990, Mappleton was under threat from losing 30 houses along the
coast of Holderness. Its main road, the busy B1482, would´ve
disappeared into the sea and would be very expensive to rebuild. So, a
coastal management scheme was set up. Blocks of granite were
imported from Norway so two groynes could be built. This would trap
the beach sediment that is being eroded away due to longshore drift.
This would then absorb some of the energy from the waves so less
energy would be directed on the cliff's side. This would reduce
erosion.
Mappleton
Coastal Management
In 1991 two rock groynes and a rock revetment were built, as
a consequence a substantial beach accumulated between the
groynes halting erosion. However, further south the rate of
erosion has increased significantly. This is because material
which is being carried south is not being replaced (it is
trapped within the groynes). Therefore there is no beach to
protect the cliffs. Even during a neap tide ( a tide which is
30% less than the average tidal range) the sea reaches the
base of the soft cliffs and erosion occurs.
Mappleton’s coastal defences
The rock groynes prevent longshore drift
and encourage deposition of sediment. This
creates a beach and a natural barrier that
prevents waves from breaking directly on
the cliff base. This therefore prevents
erosion.
However, further south towards
Withernsea erosion has been
increased – Why ??
No beach, no defence !
The process of longshore drift can no longer transport material along the
coastline to be deposited at the base of the cliffs. All the sand has
gathered at Mappleton, this leaves the glacial till cliffs exposed to the sea.
The rates of erosion just south of Mappleton have in places been as much as
10 metres per year. People have lost their homes, farmland and livelihoods.
Spurn Point
• Spurn Point is a narrow
sandy coastal spit
aproximately five
kilometers long. It is
located on the southeastern tip of the
Holderness plain which
forms the northern
banks of the Humber
estuary.
• Spurn Point is a feature
of coastal deposition and
reguires a constant
supply of sediment from
the process of longshore
drift.
Spurn Point
The strategic position of the sand spit,
guarding the entrance to a major
waterway lead to its use as a position for
shipping beacons and lighthouses.
Historical accounts of settlements and
lighthouses, particularly accounts of
their destruction and the break up of
the spit have enabled us to discover that
over the last 1000 years there have been
five 'Spurn points'. Each spit has grown
until it has become unstable, been
destroyed and then rebuilt slightly to
the west of the former one, the cycles
lasting approximately 250 years. The
current spit is nearing the end of the
cycle, and despite considerable coastal
defences the neck is in continual danger
of being breached.
Why protect Spurn Point ?
Spurn Point protects many wildlife
habitats and ecosystems which have
developed behind the spit. Spurn Point
itself has essential services such as the
Lifeguard station.
Many wooden groynes and other coastal
defences have been built to protect and
preserve the spit.
However if sediment is prevented from
reaching Spurn Point the consequences
could be immense.
Implications of protecting
the Holderness Coastline
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Saved the village and road. Mappleton row has a beach and a
growing tourist trade. But - local downstream farmers are losing
land at an even quicker rate. The farmers profits are being
threatened.
Withernsea, a large resort town, has now to spend millions to
build toe revetment sea defences to protect the town. This is
very costly.
Industry at Easington is being threatened with the gas terminals
coming too close to the sea. This is not only dangerous but could
force the gas terminal to close with the loss of 1000s of jobs
Essential services at Spurn Point (Coastguard, Lifeboat) are now
threatened as the spit is being starved of material.
Wildlife to the rear of the Spit is losing a good migrating spot.
These species are seen even less in the area.
Long term effects on King' s Lynn and Amsterdam have yet to be
analysed but they may need to take on extra sea defences
Summary
• The Holderness Coastline is shaped by erosion,
transportation and deposition. These work together to
create a variety of coastal features (caves, stacks, beaches,
spits).
• Erosional processes (corrasion, corrosion, attrition and
hydraulic pressure) produce some interesting features
especially at Flamborough Head. They also cause many
problems further down the coast where the geology is less
resistant (Mappleton, Hornsea).
• Coastal defences include wooden groynes, rock gabions,
concrete sea walls and the beach. Developing these in
certain areas however has important implications further
along the coast.
• However careful planning is needed to ensure that the whole
coast is managed in the most sustainable manner.
• Study the guide for the coastal landscape and process
enquiry carefully, this will be an assessed piece of work.
Now, if there’s time watch the video shifting sand
Re draw map slide 3 and 5
Slide 7
Same map from 3 on slide 8
http://www.flickr.com/photos/18748521@N00/2811995240/ - slide 1 picture
http://www.flickr.com/photos/18748521@N00/2811968788/ - slide 1 picture
http://www.flickr.com/photos/theevilmightyf/646771641/ - slide 10 picture
http://www.flickr.com/photos/30242985@N05/2833438448/ - slide 12 picture
http://www.flickr.com/photos/algreen/2604660469/in/set-72157601099643403/ - slide 13
picture
http://www.flickr.com/photos/hairy_rob/1320672526/ - slide 15 picture
http://www.flickr.com/photos/norfolkodyssey/1847335412/ - slide 15 picture
http://www.flickr.com/photos/algreen/2605488738/ - slide 16
http://www.flickr.com/photos/algreen/2604659969/in/set-72157601099643403/ - slide 18
http://www.flickr.com/photos/woolyman/2576853677/ - slide 20 picture
http://www.flickr.com/photos/25420869@N08/2427290163/ - slide 22 picture
http://www.flickr.com/photos/18748521@N00/2811963136/ - slide 23 picture
http://www.flickr.com/photos/25420869@N08/247288359/ - slide 24 picture
http://www.flickr.com/photos/16328806@N03/2521807985/ - slide 27 picture