2. Learning Objectives
• Demonstrate an understanding of wave
refraction
• Develop an awareness of littoral cells and
different types of sediment
• Demonstrate a knowledge of coastal
processes including erosion
• Evaluate the concepts behind mass
movement
3. Wave Refraction
• As waves leave deep water they become
affected by frictional drag as they come
into contact with the seabed
4. Sediment Sources
• Erosion of the cliffs can provide direct
sediment input
• currents bring in material from the sea bed
• Rivers bring sediment downstream
• There are several methods by which
sediment can reach the sea
5. What happens to sediment
• Sediment is either stored as a depositional
landform
• As a nearshore feature such a bank or
offshore bar.
• Alternatively it is transported as a
throughput and become outputs from the
system being deposited either in deeper
water or away from the coastal area in
question.
6. Types of Sediment
• Clastic and Biogenic sediment
• Clastic sediments are from rock
weathering and erosion
• Biogenic sediments are the shells and
skeletons of marine organisms
7. Sediment Transport and
Deposition
• What do you think is the main agent of
moving sediment and depositation?
• Waves, currents, tides and wind move
sediment from source areas and deposit it
in the form of coastal land forms
• These exist in a state of “Dynamic
Equilibrium”
8. Sediment Cells/ Littoral Cells
• These depositional landforms (such as
beaches, sand dunes, salt marshes and
mudflats) act as a dynamic sediment store
and sediments are transported onshore,
offshore, and alongshore to create them.
• These stores in turn provide sediment for
stores further down the coast.
• The next slide explains this
11. Definitions
• The movement of sand and shingle in the nearshore zone
by longshore drift (littoral drift) has been found to occur in
discrete, functionally separate sediment cells.
• There are 11around England and Wales. Smaller ones are
within these.
• The main cells are defined as a length of coastline and its
associated nearshore area within which the movement of
coarse sediment (sand and shingle) is largely self
contained.
• Interruptions to movement of sand and shingle within one
cell should not affect beaches in an adjacent sediment Cell
12. Transport
• As the particles are moved they become
rounded by Attrition.
• Larger sediment is deposited during high
energy and form beaches whilst some are
also carried in suspension in areas of
reduced energy
• Adjustments to these dynamic
environments happen continuously to
maintain the flux
13. Coastal Processes
• Now for the fun bit
• Coastlines differ due to differing erosion
• Coastal Erosion is the wearing away of the
land by the sea.
• Different types of rocks wear away at
different speeds and in different ways.
14. Types of erosion
• Hydraulic Action. This is the force of
water hitting the cliff and squeezing air into
the cracks in the rock
• Abrasion. This is the force of the bits of
rock carried in the water blasting into the
cliff.
• Attrition. This is the process of rocks
hitting each other and breaking into
smaller rocks
• Corrosion. This is a chemical reaction
between the sea water and the minerals in
the rocks
15. The secret art
of Coastal kung fu!
• Hydraulic Action: make punching movements with hand-
demonstrates force of water hitting cliff.
• Abrasion: make a throwing gesture with hands like you are
throwing dealing cards very rapidly
• Attrition: make 2 fists, and then bring them towards each
other, hitting each other, then open hand to resemble a stone
breaking.
• Corrosion: have arms out stretched in front of you, waving
fingers, and moving arms downwards. Sound effect of
something dissolving is needed.
• Solution: Put arms out in front of you waving fingers and
moving down.
16. Please Don’t be embarrassed
• Oh OK be embarrassed then
• Here we go:
18. Soil Creep
• Slow less than 1cm a year
• Caused by raindrop impacts
• Wet periods add moisture to soil which
swells and expands then falls down slope
• Freeze thaw
19. Solifluction
• Occurs mainly in colder areas, where freeze and then thaw
creates movement due to lack of percolation
20. Earth flows and Mudflows, slides
slumps and Rockfalls
• Faster movements
• Occur on steep slopes
• Found often on unconsolidated slopes
• Can be large or small
21. Other Mass Movement Reasons
• Students are to write short paragraphs on
the following separate into physical and
human causes
• Runoff
• Marine Erosion
• Waves and Beaches
• Geology
• Human Activity
• Sea walls and Coastal Defences
• Land reclamation
• Development
22. Learning Objectives
Demonstrate an understanding of wave
refraction
Develop an awareness of littoral cells and
different types of sediment
Demonstrate a knowledge of coastal
processes including erosion
Evaluate the concepts behind mass
movement
