The document discusses coastal environments and processes. It begins by defining a coast and describing the different zones and landforms that make up coasts, such as beaches, headlands, and cliffs. It then explains how coasts are dynamic environments that change over time due to various natural processes and forces, including waves, tides, currents, geology, and ecosystems. Specific coastal erosional processes like corrasion, attrition, solution, and hydraulic action are also outlined.

1. CHAPTER 7:
COASTS
Jurassic Coast

2. Balos Lagoon, Crete, Greece

3. Island in Krabi, Thailand

4. British Isles

5. Tropea, Calabria, Southern Italy

6. Coastal
Environments
Definition of coast
Why and how are they
different and dynamic?
La Grotta Cove, Corfu Island, Greece

7. What is a coast?
— A coast is a zone where the land meets and interacts
with the sea (waves and tides).
— The coast is divided into various zones. The outline of a
coast (coastline) is usually seen at the mean sea level.
Low-­‐%de
Low-­‐%de
5

8. What is a coast?
— A coast may be made up of landforms
(such as beaches, headlands and cliffs) as
different factors and processes interact
with each other.
Cliffed (Bunda cliff
coastline in Australia)
Sandy beach (Cala Binimel-La in
Menorca, Spain)
Headland (Durdle Door in
Dorset, England)

9. Dynamic nature of coasts
— Coastal environments are
ever-changing.
— Coastal environments
vary from place to place.
Durdle Door (a natural limestone arch
near Lulworth in Dorset, England)
Lulworth Cove (cove, formed as a
result of wave diffraction, in Dorset,
southern England)
Before the collapse in 2002
8 Apostles (in Australia)
After the collapse in 2012
6

10. Factors affecting coasts
— Natural processes
— Waves –
— When wind blow across the sea surface, energy is
transferred to the water.
— The wind energy possessed by the waves will affect
how it approaches and interact with the coast when
it hits the land.
7

11. Factors affecting coasts
— Natural processes
— Waves
— Tides and sea level changes –
— The daily rise and fall in the sea level affects process such
as coastal erosion, sediment transport and deposition.
— During high tides, waves have a higher capacity
to erode and transport more sediments away from
large parts of the coasts.
— They are also able to reach further inland which are
not subjected to wave action at low tides.
7

12. Factors affecting coasts
— Natural processes
— Waves
— Tides and sea level changes
— Currents –
— Driven largely by prevailing winds, ocean
currents currents distribute large amounts of energy
and shapes the coast through processes of coastal
erosion, sediment transport and deposition.
— Currents are flows of water that move horizontally or
vertically in a certain direction.
7

13. This high area can only be reached
and eroded during high tide.
Currents as agents of erosion:
— There are different types of currents.
— Eg.Tidal currents: currents affected by tides.
— The coast experiences a high tide or a low tide every 12 hours.
— They affect the part of the coast that can be reached by the
waves.
High
Tide
Low
Tide

14. Factors affecting coasts
— Natural processes
— Waves
— Tides and sea level changes
— Currents
— Geology –
— Rock composition determines rock hardness and their resistance
to erosion, thus affecting the rate of change along coasts.
— More resistant rocks (eg. granite and basalt) erode slower
than less resistant rocks (eg. limestone and shale) which are
more susceptible wave attack and erosion.
7

15. Factors affecting coasts
— Natural processes
— Waves
— Tides and sea level changes
— Currents
— Geology
— Ecosystem type –
— Coastal ecosystems affect the rate of change of coastal
environments by reducing the impacts of waves on coasts.
— Coral reefs act as natural barriers that slow down the speed and
impacts of waves on the coastline.
— Mangroves trap sediments with their aerial roots, reducing
coastal erosion, and even extending the coastline seaward.
8
Bora Bora,
French Polynesia

16. Factors affecting coasts
— Human Activities
— Building port facilities for livelihood and trading purposes.
— Building marinas (dock for boats/yachts) for recreational activities.
— Tourists dumping waste also cause pollution on beach
environments.
Coastal
Modifica-on
(Burt
Palm
Island,
Dubai)
8

17. Berlenga Island, Peniche, Portugal

18. Bondi Beach, Sydney, Australia

19. Hotel Hospes Maricel,
Mallorca, Spain
Ithaca island, Greece

20. Sea Waves
How are waves generated?
What factors influence them?
What are the different
types of waves?

21. Waves
— Waves develop when the energy from wind blowing
across seas is transferred to the water surface.
— The direction of wind affects the movement of waves.
— Onshore winds push waves towards the coast,
resulting in waves crashing onto the shore.
— Waves are also agents of erosion:
àWhether waves can erode a coast depends on the
amount of energy they possess.
àThe larger the waves, the more energy they possess,
and hence their eroding ability increases.
9

22. Wave terminology
— Various parts of a wave:
— Crest – highest part of a wave
9

23. Wave terminology
— Various parts of a wave:
— Crest
— Trough – lowest part of a wave
9

24. Wave terminology
— Various parts of a wave:
— Crest
— Trough
— Wave length –
horizontal distance from
crest to crest /
trough to trough
9

25. Wave terminology
— Various parts of a wave:
— Crest
— Trough
— Wave length
— Wave height – vertical
distance between crest
and trough
9

26. Wave terminology
— Various parts of a wave:
— Crest
— Trough
— Wave length
— Wave height
— Wave frequency –
number of wave crest
that passes a fixed point
9

27. Factors affecting size of waves
— Wave energy:
— Wind is air moving from a region of high pressure to a
region of low pressure.
— Greater difference in pressures
à greater the wind speed à higher wind energy
à formation of large waves.
— The amount of wave energy is seen from wave steepness
and wave period.
— The higher the wave energy, the steeper the wave and
short the wave period.
10

28. Factors affecting size and wave energy
— Wind speed – the faster the wind blows, the greater the
wind energy possessed by the waves.
— Duration of wind – the longer the wind blows, the
larger the waves become.
— Fetch (the distance over which winds blows across open water to
form waves) – the longer the fetch, the bigger the waves.
10

29. Factors affecting size and wave energy
— Natural events (such as tsunamis)
— Human events (such as sea traffic)
Taken at Ao Nang,
Krabi Province,
Thailand, during the
2004 Indian Ocean
earthquake and
tsunami in Thailand

30. Waves in the open ocean
— Long wave length
— Low wave height
— Water particles in the open ocean move in an orbit,
whose motion decreases with depth.
11

31. Waves close to the coastline
— As waves enter shallow water, they slow down,
grow taller and change shape.
— (1)At a depth of half its wave length, the rounded
waves start to rise as the waves interact with the sea bed.
11

32. Breaking
waves
Waves feel bottom
and steepen
Deep water waves
not affected by bottom
— (2)As we go nearer the coastline, the base of the wave
experiences friction with the shallow sea bed.
— Friction causes the base of the wave to lose energy,
and thus the base slows down.
Waves close to the coastline 11

33. Waves close to the coastline
— (3)The back of wave moves faster than the front
à it keeps pushing it forward
à the wave is forced to rise (steepness increase).
— (4)When the wave becomes too steep, it eventually
collapses
and breaks
onto the
beach.
11

34. Waves close to the coastline
— When waves break, they release energy on the coast,
breaking down rocks along the coastline into smaller
particles.
— àThese particles
are then subjected
to coastal processes
(erosion, deposition,
transport), and are
moved to other
parts of the coast.
12

35. — Nearer the coastline:
àWave height increases – WHY?
àWave length decreases
Waves close to the coastline – Recap
Approaching shallow water, wavelength decreases, wave height
increases

36. — When waves break,
water rushes up the beach.
— This forward movement of
a wave onto the beach is
known as swash.
— à Swash brings materials
(sediments) onto the beach.
Swash and Backwash
Swash
12

37. — As swash moves up the coast,
wave energy is gradually lost
as gravity causes the wave to
be pulled back into the sea.
— This backward movement
of the wave into the sea is
called a backwash.
— à Backwash moves materials
away from the beach.
Swash and Backwash
Backwash
12

38. Identify the crest, swash and backwash of the wave.
swash
backwash

39. Types of waves: Constructive Wave J
— Aka swells and spilling breakers.
— Constructive waves are low-energy waves where
the swash is stronger than the backwash.
— Constructive waves break far from the shore.
— Strong swash pushes material up the beach.
— Backwash is weak as the wave has spent most of its
energy overcoming friction with the shallow seabed.
— When the backwash returns to the sea, some
sediments are left on the coast (ie. deposited).
12

40. — Strong swash deposits sediments on the coast
+ weak backwash removes little materials
à builds up coast by deposition of sediments
à commonly forms sandy beaches
— This usually
occurs on a
gently sloping
beach.
Types of waves: Constructive Wave J
12

41. — Aka plunging and surging breakers.
— Destructive waves are large/high-energy waves
where the backwash is stronger than the swash.
— High energy waves are associated with storms.
— The strong backwash transports rocks and beach
material away from the beach efficiently.
— The weak swash deposits lesser material than what is
transported away.
Types of waves: Destructive Wave L
12

42. — Strong backwash erode coasts
+ weak swash deposits little material
à does not build beaches effectively.
— Occurs where there
is usually a steep
slope that causes
the waves to break.
Types of waves: Destructive Wave L
12

43. — Low gradient, low energy
— Small waves, low wave height
— Long wave length
— Wave frequency: 6-8 per min
— Swash > backwash
— Gentle coastal slope
— Deposition
— High gradient, high energy
— Large waves, high wave height
— Short wave length
— Wave frequency: 10-14 per min
— Backwash > swash
— Steep coastal slope
— Erosion
Types of waves: a comparison 13

44. — The process by which waves change direction as they approach the
coast.
Wave refraction
Waves tend to
converge as
they approach
headlands.
• Increased wave height
• Greater erosive energy
• Energy concentrates on
the headland à erosion
13

45. — The process by which waves change direction as they approach the
coast.
Wave refraction
Waves tend to
diverge as
they approach
bays.
• Decreased wave height
• Reduced erosive energy
• Energy spreads out à deposition in bays
13

46. Zakynthos, Greece

47. Coastal Processes
These processes operate
at varying degrees,
causing changes to
coastal landforms and
features over time.
Point Udall, St. Croix, USVI - the eastern
most point in U.S. territories

48. Coastal Processes
— (a) Coastal EROSION
à Process which results in removal of materials* from
a coast.
— (b) Sediment DEPOSITION
à Process which results in materials* being added to a
coast.
— (c) Sediment TRANSPORTATION
à Process where materials* are moved along the coast.
*Materials are for example sand and sediments.
15

49. (a) Coastal Erosional Processes: CASH
— Corrasion /Abrasion
— The waves throw rock particles at the coast
when the waves break on the cliff face.
— These rock particles knock and scrape against the
coastal cliffs.
— This breaks of pieces of rocks from the cliff, slowly
eroding it away.
15

50. (a) Coastal Erosional Processes: CASH
— Attrition
— Rocks and pebbles collide with each other
as they are carried by waves.
— They break down into smaller pieces,
becoming smoother, smaller and rounded over
time.
15

51. (a) Coastal Erosional Processes: CASH
— Solution / Corrosion
— Acids contained in sea water will slowly dissolve
minerals in certain types of rocks (eg. limestone
rocks are easily dissolved by carbonic acid).
— When rock minerals undergo solution, they become
weaker and more susceptible to disintegration.
15

52. (a) Coastal Erosional Processes: CASH
— Hydraulic action
— The force of the waves compresses the air found in
cracks in the rocks.
— Overtime, this creates tremendous pressure along the
joints of surrounding rocks.
— The air then expands explosively, forcing out pieces
of rocks, thus breaking them into smaller pieces.
One or more of these erosional process may take place
simultaneously at any one coastal location. 15

53. (b) Sediment Deposition
— Depends on sediment size:
— The laying down of sediments along the coast
occurs when waves are no longer able to carry
the sediments (eg. when wave energy decreases).
— Large and heavy sediments are laid down/
deposited first.
Silt
18

54. (b) Sediment Deposition
— Depends on sediment size:
— What do you think is the sequence of deposition?
— Which will be deposited first and which will be last?
Silt
18

55. (b) Sediment Deposition
— Wave size and energy:
— Small or low-energy waves (caused by weak
winds/short fetch) have a stronger swash than
backwash.
— Stronger swash piles/deposits more material on
the shore than it takes away during the backwash.
— àWhen the backwash returns to the sea, some
sediments are left behind on the coast.
18

56. (b) Sediment Deposition
— Depends on location and type of coast:
— Deposition occurs on gently sloping beaches and sheltered
coasts.
— Deposition predominates as the backwash is weak
because wave has spent energy overcoming friction with
shallow seabed. Watermouth Valley, Ilfraco, UK
(a coastal campsite)
18

57. — Sediments are transported along coasts through two
related processes:
(i) Beach Drift
— Sediments move up
the beach at an angle
as swash (AàB).
— It then moves
perpendicularly
down the beach
(BàC) as backwash.
(c) SedimentTransport – (i) Beach Drift 16

58. (c) SedimentTransport – (ii) Longshore Currents
— Sediments are transported along coasts through two
related processes:
(ii) Longshore Currents
— As waves approach the
coast at an angle, they
generate LS currents in
the nearshore zone,
moving and transporting
materials along the shore.
— These currents flows
parallel to the coast.
16

59. — The processes of (i) beach drift and
(ii) longshore currents work together to produce a
sediment movement called Longshore Drift.
— Longshore Drift is most rapid
when waves approach a
straight coast at
40o – 50o.
(c) SedimentTransport – Longshore Drift 16

60. (c) SedimentTransport – Longshore Drift 16
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61. (c) SedimentTransport – Longshore Drift 16
Beach
Drift
Longshore
Currents
Swash
and
Backwash
Zig-­‐zag
movement
Parallel
to
coast
40o
–
50o