Coastal Processes, Patterns and
Landforms
Objectives
• Discuss the processes of coastal erosion, transportation and
deposition.
• Understand the formation of coastal landforms and identify these
on diagrams, maps and photographs.
• Describe how human activities can affect natural coastal
processes.
• Discuss and describe the threats to the coastline and the
methods used to protect it.
• Explain how changes in sea levels affect coastal landforms.
Activity
• Mind map everything you remember about
the coast!
Waves
• Two types of waves – Constructive and Destructive
• The size of the wave is influenced by the fetch. The
distance a wave has to travel before it reaches land.
• When waves break water rushes up the beach called
the swash. When the water goes back to the sea its
called backwash.
Destructive Waves
• (i) the strength and speed of the wind – when the
wind is fast, more energy is transferred and therefore
the bigger the wave is produced.
• (ii) the duration of the wind –when the wind
remains strong over long periods- the longer the
wind blows, the more energy is transferred to the
wave
• Destructive waves = erosion
• The backwash digs into the land removing large
quantities of rock, sand and earth.
Destructive waves

Weak swash

Strong back wash

Operate during storm conditions

Erosion
Constructive Waves
• Powerful swash that can carry debris up the
beach but have little energy left in the
backwash to drag the debris away again.
• Constructive waves = deposition
Constructive waves

Strong swash

Weak backwash

Make storm beaches

Deposition
Wave Refraction
• Wave refraction is the bending of the waves.
• The waves approaching the coast are straight.
Friction with the sea bed causes part of the
wave near the headland to slow down while
the rest of the wave continues at the same
speed.
• The difference in speed makes the wave curve
towards the headland.
Coastal Erosion
• Processes
• Landforms (Essay Questions)
• Identifying on OS and Aerial Photograph
Sea Erosion

http://www.bbc.co.uk/schools/gcsebitesiz
e/geography/coasts/coastal_processes_re
v3.shtml
Can any one guess what the processes of
sea erosion are?
Hint: very similar to river erosion.
Processes of Coastal Erosion
1)
2)
3)
4)
5)
Hydraulic Action
Compression
Abrasion
Attrition
Solution
Hydraulic Action
• When strong waves crash against the coast
they break rocks off the cliff face.
Compression
• Air Compression – The waves trap air in crack
in the rocks. As the waves retreat the trapped
air expand quickly and can crack the rock.
Abrasion
• This is erosion caused by small rocks carried in
the sea water hitting against the coastline.
p99
*Very similar to Hydraulic Action.
Difference = water contains suspended rock
material.
Attrition
• Erosion caused by the small stones hitting
each other breaking themselves into smaller
pieces.
Solution
• Salts in the sea water dissolve rock by
chemical means. Chalk and limestone coasts
are most easily eroded this way.
Activity
• Write the processes of erosion into your
copies. Learn for homework.
Examples of coastal landforms formed by
erosion and deposition
Landforms of Sea Erosion
•
Like rivers, the sea creates many features or
landforms as a result of erosion. These include,
1. Cliffs and blowholes.
2. Bays and Headlands
3. Sea caves, sea arch, sea stack, sea stump
Each of these will be a long answer essay. You will also
be required to recognise these on a map/photo and
diagram.
The Sea/ The Coast
• Cliff – close contour lines at the edge of the
land near water.
How are cliffs and wave-cut platforms formed?
Cliffs and Wave-cut platforms
The waves attack the base of the cliff through the processes of abrasion, compression,
hydraulic action and attrition.
Over time the cliff will be undercut and a wave-cut notch is formed.
Eventually the cliff becomes unstable and collapses. Further cliff retreat will form a wavecut platform.
Blowhole

This is a passage that
links the roof of a cave to
the cliff top.

Air trapped by waves
erodes away the rock.

This continues to create a
tunnel called a blowhole.
http://www.youtube.com/w
atch?v=bWC_g2XfuQU
Activity
• Read the formation of a cliff in your groups.
Hightlight the important information.
• Homework: Write out a sample answer of a
cliff and wavecut platform. Use F.E.E.D
• Name the feature, example, explain and
diagram.
Sea Cave, Sea Arch, Sea Stack

http://www.boardworks.co.uk/media/2132
de4b/ALevel%20Geography%20Sample/2
_9_stacks_stumps_animation.swf
Sea Caves, Sea Archs, Sea Stacks
• As the water smashes up against the headland
rock, the erosion process begins.
• Waves chisel away at the rock and over time a
cave is formed.
• The cave will give way and the water will drill
its way on through the back of the cave, thus
creating an arch.
• Overtime the arch collapses to reveal one
large stack of rock. This is the sea stack.
Sea Stacks
Sea Caves, Arches, Stacks and Stumps.
• Stack little islands – green with blue outline.
• Stumps underwater, smaller, grey.
*Difficult to see an arch or cave.
For Homework
• Write out sample answers on Sea cave, arch
and stacks using the FEED principal.
• F = State the Feature
• E = Explanation/Formation
• E = Examples
• D = Labelled Diagram
Bays and Headlands
http://www.youtube.com/watch?v=C_4DEkz9CCU
• In your groups read how bays and headlands
are formed. Highlight the important parts.
For Homework
• Write out sample answer on Cliffs and Sea
Stacks using the FEED principal.
• F = State the Feature
• E = Explanation/Formation
• E = Examples
• D = Labelled Diagram
Deposition
Constructive Waves
• Powerful swash that can carry debris up the
beach but have little energy left in the
backwash to drag the debris away again.
• Constructive waves = deposition
Before we talk about deposition we have to
mention how the eroded material is carried
along the coast.
• What do you remember about longshore drift??
• Movement of material along the coast.
• Occurs because the coastline is irregular and waves do
not break parallel to the coast (wave refraction).
• Swash moves material to the shore at an angle and the
backwash pulls the sediment back out to sea at a right
angle.

http://www.youtube.com/watch?v=U9EhV
a4MmEs
Longshore Drift

http://www.youtube.com/watch?v=rCpZYlPqn6E
Activity:
Read your book - page 55.
Draw the diagram no.6 on page 55 of your
book.
Longshore Drift
• http://www.youtube.com/watch?v=U9EhVa4
MmEs&feature=related
• Activity: Using the above information and
notes in your book. Summarise longshore drift
into your copies
Landforms of coastal deposition
1)
Beaches
2)
Sand Spits, Sand Bar and Lagoon
3)
Tombolos
Beaches form in sheltered environments, such as
bays. When the swash is stronger than the
backwash, deposition occurs.
Beach
• Can be seen on an OS map – coloured yellow at the coast
• Beaches have other landforms such as Berms, Cusps and Runnels
and Ridges.
• Berms: are long steps or terraces which form on shingle beaches
when constructive waves push beach sediment into long low
ridges. They mark the junction between the backshore and
foreshore.
• Cusps: Crescent shaped hollows formed where shingle changes to
sand. Generally occur on pebble beaches
• Runnels and Ridges: Runnels are wide depressions in the sand of
the foreshore. Ridges are gentle rises in it. Formed by the action of
constructive waves.
Activity
• Read the notes in book about the formation of
a beach.
• Complete a sample answer into your copies
using F.E.E.D and remember at least 13 SRPS.
Sand Spit
• A long deposit of sand attached to the land at one
end.
• Example: Portmarnock and North Bull Island in
Dublin.
• Created when the process of longshore drift is
interrupted in some way either by a change in the
shape of the coast or by human activity such as
building a sea wall .
• They are commonly found attached to the headland.
Sand Bar and Lagoon
• When a spit grows and reaches out to the
other side the spit is called a sand bar.
• If it cuts water off from the sea a lake is
formed called a lagoon.
Tombolo
• When a spit grows out into the ocean and
joins to an island its called a tombolo.
Homework
• Write out the sample answer for sea spit,
baymouth bar, lagoon and tombolo.
• Use the F.E.E.D principle and remember 15
SRPS!
Human Interaction with the Coast
•
•
•
•
•
•
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•
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Fences
Mats
Beach nourishment
Groynes
Sea walls
Rock armour
Revetments
Breakwaters
Gabions
Coastal Defence
•
When managing the coastline there are two main
options:
1. HARD
This is where man made coastal defence structures
are used to reflect large amounts of wave energy
and hence protect the coastline.
Sea Walls, Rock Armour, Breakwaters and Gambions
SOFT ENGINEERING
2.This is where beaches or naturally formed
materials are used to control / re-direct
erosion processes. Designed to encourage
beaches and dunes to form or get bigger
Fences in sand dunes, mats, Beach nourishment
and groynes
HARD COASTAL PROTECTION
METHODS
1. Sea Wall
Sea walls
Re-Curved Sea Wall
• - concrete wall which is curved on the underside to
deflect the power of the waves
• these can be very expensive and the deflected waves
can scour material at the base of the wall causing
them to become undermined
these are however a very effective means of
preventing erosion and they reflect rather than
absorb wave energy.
2. ROCK ARMOUR
Boulders
Rock Armour
• large boulders on the beach absorb wave energy and break
the power of the waves
• - although movement of the boulders is expensive this can be
a much cheaper method than some other solutions
• - the boulders can however be undermined easily by waves
washing away sand and shingle beneath them. They also can
be quite ugly, changing the appearance of a coastline.
4. Gabions
Gabions
• these cages of boulders are built into cliff
faces to protect the cliff from the force of the
waves;
- they are cheaper than sea walls and can be
very effective where severe erosion is a
problem
- they are however visually intrusive
5. Revetments
Revetments
• these wooden structures break the force of waves
and beach material builds up behind them
- they are cheap and effective at breaking waves
- as well as being visually intrusive however they do
need replacing more frequently than most other
defence methods.
Breakwaters
• Concrete walls built some distance offshore to
reduce the force of the waves.
Soft Engineering Techniques
Soft Engineering Techniques
• Soft engineering includes beach replenishment in
which beach material is added to provide a "natural
solution". Environmentally this is a preferred option
as it maintains the beauty of the landscape and
avoids visual intrusion, however it can be expensive
to maintain as longshore drift continues to move
beach material down the coast and therefore regular
replenishment is required.
• Sand Dunes and salt marshes can also be encouraged
to act as natural barriers to the waves.
Fences and Mats
• Encourage build up of wind blown sand in
dunes
• Mats are placed in front of dunes. They trap
sand and encourage plant growth
Groynes
Groynes
3. Groynes
• these structures (usually either wooden or
steel) are designed to top longshore drift and
therefore act to build up and anchor beach
material, protecting the base of cliffs.
Groynes
• they are effective at reducing erosion in the area
they are constructed in by causing significant build
up of beach material
- groynes may however starve areas further down
the coast of material by stopping longshore drift,
resulting in an increase in erosion in these areas
Case Study of Human Interaction
• Read the handout of human interaction in
Courtown north beach Co. Wexford.
Isostatic and Eustatic Processes
• Isostatic processes involve adjustments to the
balance between land and the sea.
• The balance may change over time.
Did you know that in some coastal areas
beaches and cliffs can be seen above the
present sea level.
Two processes occur which lead to changes in land and
sea level
Keywords
•
•
•
•
Eustatic/ eustacy
Submerged coastlines
Isostatic/ isostacy
Emerged coastlines
Eustatic changes/ Eustacy
• Sea levels rise or fall
• During an ice age sea level drops because rain and
river water is locked away in the ice sheets and do not
reach the sea.
• When the ice melts large volumes of meltwater flow
into the sea and cause a global rise in sea levels.
• Submerged coastlines when the coastal areas are
drowned by the water.
Isostatic Change/ Isostacy
• Land rises or falls
• The earth’s crust floats on the liquid mantle.
The weight of huge ice sheets on the land can
cause the earth’s crust to push into the
mantle.
• This is like a plastic duck floating in water.
When you push down on the duck the duck
will go underneath the water.
• When the ice melted the weight was removed
from the earth and the crust returns to its
original level raising the land out of the sea.
• These are all local actions. The local change in
sea level is called isostatic sea level chanage.
• Coastal area that are raised from the sea by
isostacy are known as emerged coastlines.
Landforms of Submergence
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•
•
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Rias
Fjords
Fjards – submerged glacial lowlands
Dalmatian Coasts – submerged valleys
running parallel to the coast
Rias
Rias are submerged river valleys. The lowest part of the
river’s course and the floodplains alongside the river may
be completely drowned, but the higher land remains
exposed, e.g. Kingsbridge Estuary, Devon
• In cross section the ria has relatively shallow
water becoming increasingly deep towards the
centre. The exposed valley sides are quite
gently sloping.
• In long section rias are quite even with a
smooth profile and water of uniform depth.
• In plan view they tend to be winding,
reflecting the original route of the river and
its valley.
Fjords
Fjords are submerged glacial valleys. They have steep,
cliff-like valley sides and the water is uniformly deep
(often 1000m in depth). These were formed when glaciers
eroded below sea-level. When the ice melted the valleys
were flooded, e.g. Milford Sound fjord, New Zealand
• The u-shaped cross-section reflects the
original shape of the glacial valley.
• Unlike rias, fjords are not deepest at their
mouths, but have a shallow section at the
seaward end known as the threshold.
• Fjords have much straighter routes, due to
the erosive power of the glacier.
Landforms of Emergence
• Raised Beaches
• Abandoned Coastlines
Raised Beaches
Raised beaches, e.g. Little Gruinard, Ullapool are areas of
former wave-cut platforms and their beaches which are
left at a higher level than the present coastline.
Abandoned cliffs, caves and stacks can also be found.
Exam Questions
•
•
•
•
•
Have to recognise all landforms on OS maps
Landforms of erosion
Landforms of deposition
Human interaction with the coast
Changes in sea level
End of Chapter Assessment
• Traffic light the learning objectives at the start
of the chapter
• Make sure all essay questions are up to date.