CHAPTER 1
COASTS
Should Coastal
Environments Matter?
CHECK-IN: Surfing a monster wave
CHECK-IN: What are the characteristics of a
coastal environment?
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2
3
4
CHAPTER 1 COASTS
Should Coastal Environments Matter?
In this Chapter, you will explore three key
questions:
1.How and why are coastal environments
different and dynamic?
2.Why are coastal areas valuable?
3.How can we manage coastal areas in a
sustainable manner?
CHAPTER 1 COASTS
Should Coastal Environments Matter?
Gateway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently
a. What is a coastal environment? (zones)
CHAPTER 1 COASTS
Should Coastal Environments Matter?
Gateway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently
b. What is the difference between coastal
environment?
What are the differences in the characteristics of the following coastal environments?
Lulworth Cove, Britain
Waikiki Beach, Hawaii
Cape Kumukahi, Hawaii
Bunaken, Indonesia
CHAPTER 1 COASTS
Should Coastal Environments Matter?
Gateway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently
c. What factors lead to the differences and
dynamism of coastal environments?
•
•
•
•
•
Waves
Tides and sea level changes
Currents
Geology (rock composition)
Types of ecosystems (e.g. mangroves and coral
reefs)
• Human activities (e.g. trading, fishing, recreation)
c. What factors lead to the differences and
dynamism of coastal environments?
Tombolo
c. What factors lead to the differences and
dynamism of coastal environments?
Spit
c. What factors lead to the differences and
dynamism of coastal environments?
Beach
c. What factors lead to the differences and
dynamism of coastal environments?
Cliffs
c. What factors lead to the differences and
dynamism of coastal environments?
• Waves
- Wind energy transferred to
water
- Blowing across surface of seas
and oceans
Affects: the power of waves to
erode landforms
• Tides and sea level changes
- Rise/fall in sea level
- Caused by gravitational pull of moon and Sun on Earth
Affects: transportation of sediments (depositional landforms)
and erosion
c. What factors lead to the differences and
dynamism of coastal environments?
• Currents
- Large scale continuous movement of water in seas and oceans
- Driven by prevailing wind in one direction
Affects: sediment distribution and erosion
• Geology (rock
composition)
- Composition: more/less
resistant rocks; hard/soft rock
- Composition: layered structure
Affects: rate/speed of erosion
c. What factors lead to the differences and
dynamism of coastal environments?
• Types of ecosystems
- Natural barriers
- Corals: Slow down speed of waves
- Mangroves: trap sediments and
reduce coastal erosion
Affects: impact of waves on
coasts
• Human activities
- Built-up area along coastline
- Pollution of coastal environment
Affects: condition of coastal environment
Chapter 1 COASTS
Should Coastal Environments Matter?
Gateway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently
d. How do coastal processes differ?
Wave action
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3
How would you describe the waves?
2
4
d. How do coastal processes differ?
Wave action
Parts of a wave
d. How do coastal processes differ?
Why do waves curl?
1.What do the photographs definitely tell me?
2.What can I infer from the photographs?
3.What do the photographs not tell me? What further questions do I need to ask?
Photograph A
Photograph B1
Photograph B2
d. How do coastal processes differ?
Why do waves curl?
d. How do coastal processes differ?
Match the diagrams to the factors affecting wave energy
A
B
C
D
Factors
Fetch (distance the
wave travels)
Duration of wind
1
Wind speed
Wind strength
3
2
4
d. How do coastal processes differ?
Wave action
•
•
•
•
•
•
•
Swash
Backwash
Two wave types: Constructive & destructive
Erosion
Transport
Deposition
Wave refraction
d. How do coastal processes differ?
Wave type
• Constructive
– dominant process: swash carries sediments onto beach at an oblique angle)
• Destructive
– dominant process: backwash carries sediments away from beach into ocean at
a right angle due to gravity)
NOTE: A Swash and Backwash occurs for every wave that comes onto the
shore)
d. How do coastal processes differ?
Wave type
Constructive waves
Destructive waves
Gradient
Low
High
Energy environment
Low
High
Wave height
Low
High
Wave length
Long
Short
Wave frequency
6–8 per minute
10–14 per minute
Swash vs backwash
Swash more powerful than
backwash
Backwash more powerful
than swash
Breakers
Swells and spilling breakers
Plunging and surging
breakers
Occurs on
Gentle coastal slope and
sheltered coast
Steep coastal slope and open
coast
Prominent process
Deposition
Erosion
d. How do coastal processes differ?
Wave action
Wave refraction
d. How do coastal processes differ?
Wave action
• Wave refraction (approaching a coast)
- The process by which waves change direction when they approach
a coast
- Occurs only when there is friction between water and seabed
- Change in wave speed
- Waves converge on headlands and diverge on bays
- When waves converge – increased wave height and greater
erosive energy
- When waves diverge – decreased wave height and lower erosive
energy
- Uneven impact on shoreline
d. How do coastal processes differ?
Wave action
• Coastal erosion
Focus on: Cause (wave action, rock particle
movement) & Effect (outcome of wave action with
rock particles)
a.
b.
c.
d.
Hydraulic action
Abrasion or corrasion
Attrition
Solution or corrosion
d. How do coastal processes differ?
d. How do coastal processes differ?
Cliff undercut by coastal abrasion
d. How do coastal processes differ?
Rocks rounded by attrition
d. How do coastal processes differ?
Wave Action
•
Sediment Transport
– Longshore drift and longshore currents
Recap:
• Currents
- Large scale movement of water in oceans
- Driven by prevailing wind in one direction
Affects: sediment distribution and erosion
d. How do coastal processes differ?
Wave action
•
Sediment transport
– Longshore drift and longshore currents
d. How do coastal processes differ?
Wave action
• Sediment transport
-
Longshore currents and longshore drift
Longshore currents:
•
•
Flows parallel to coast, forms when waves approach coasts at an
angle
Resultant zigzag movement of sediments known as beach drift:
1.
2.
Carried up the beach at an oblique angle through swash due to wind direction
Carried perpendicularly down the beach through backwash due to gravity
d. How do coastal processes differ?
Wave action
Longshore drift:
• A result of both longshore currents and beach drift
• Sediments are deposited when they meet an obstruction. These
sediments are transported by both longshore current and beach drift,
which produces longshore drift.
• Determined by direction of wind
d. How do coastal processes differ?
Wave action
• Sediment deposition
-
-
What are some reasons for the
man being unable to carry the
boxes properly?
What should the man do if the
boxes are too much and too
heavy?
d. How do coastal processes differ?
Wave action
• Sediment deposition
- What are some reasons for the wave being unable to
carry the sediments?
- What should the wave ‘do’ if the sediments are too
much and too heavy/large?
d. How do coastal processes differ?
Wave action
•
Sediment deposition
Sediment texture
Very fine
Sediment type
Sediment size
Clay
less than 0.0039 mm
Silt
0.0039 mm to 0.0625 mm
Fine sand
0.125 mm to 0.25 mm
Medium sand
0.25 mm to 0.5 mm
Coarse sand
0.5 mm to 1 mm
Very coarse sand
1 mm to 2 mm
Pebble
2 mm to 64 mm
Cobble
64 mm to 256 mm
Boulder
more than 256 mm
Chapter 1 COASTS
Should Coastal Environments Matter?
Gateway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently
e. How do coastal processes shape coastal landforms
differently
Coastal features/landforms: Process leads to an
outcome/characteristic of landform
•Cliffs and shore platforms
•Headlands and bays
•Caves, arches and stacks
•Beaches
•Spits and tombolos
e. How do coastal processes shape coastal
landforms differently
Coastal features/landforms: Process leads to an
outcome/characteristic of landform
•Cliffs and shore platforms
-
Hydraulic action
-
Erosion by waves
-
Enlarged joints
-
Notch
-
Cliff collapse and cliff
retreat
-
Gently-sloping platform at
cliff base
e. How do coastal processes shape coastal
landforms differently
Coastal features/landforms: process leads to an
outcome/characteristic of landform
• Headlands and bays
-
Different rates of
erosion on rocks of
different resistance
-
Bays (wide indented
inlets in the coastline)
-
Headlands (rocks
which extend into
sea)
e. How do coastal processes shape coastal
landforms differently
Coastal features/landforms: process leads to an
outcome/characteristic of landform
• Caves, arches and stacks
-
Further erosion of
headlands (abrasion and
hydraulic action)
-
‘Hollowing’ by wave action
-
Roof of cave collapses
-
Lines of weaknesses
-
Cave
-
Stack (pillar of rock)
e. How do coastal processes shape coastal
landforms differently
Coastal features/landforms: process leads to an
outcome/characteristic of landform
• Beaches
-
Deposition of different
sized particles
-
Erosion by strong waves
-
Zone of deposition
-
Made of loose sand, gravel
and pebbles
-
Gentle gradient (fine
grains)
-
Steep gradient (coarse
grains)
e. How do coastal processes shape coastal
landforms differently
Coastal features/landforms: process leads to an
outcome/characteristic of landform
• Spits and Tombolos
-
Longshore drift
-
Deposition and
transportation
-
Continued longshore
drift even though
coastline changes
abruptly
-
Accumulated materials
-
Spits/tombolos
CHAPTER 1 COASTS
Should Coastal Environments Matter?
Gatway 1: How and why are coastal
environments different and dynamic?
a.
b.
c.
d.
e.
What is a coastal environment? (zones)
What are the differences within coastal environments?
What factors lead to the difference and dynamism in
coastal environments?
How do coastal processes differ?
How do coastal processes shape coastal landforms
differently