Upper Sec Physical Geog

1. PAYA LEBAR METHODIST GIRLS’ SCHOOL (SECONDARY)
Sec 3 Express Pure Geography
Coasts
Geographer: ________________________( ) Date: _______________
Class: ___________
DYNAMIC
NATURE
of
coastal
environments
[tb
pg
6]:
 Coastal
environments
change
over
time
(constantly
changing).
 Coastal
environments
vary
from
place
to
place.
Coastal
environments
are
dynamic
and
ever-­‐changing
due
to
the
following
FACTORS
AFFECTING
COASTS*
[tb
pg
7-­‐8]:
Natural
factors
1.
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.
2.
Tides
and
sea
level
change
• 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
that
are
not
subjected
to
wave
action
at
low
tides.
3.
Currents
• Currents
are
flows
of
water
that
move
horizontally
or
vertically
in
a
certain
direction.
• Driven
largely
by
prevailing
winds,
ocean
currents
distribute
large
amounts
of
energy
and
shape
the
coast
through
processes
of
coastal
erosion,
sediment
transport
and
deposition.
4.
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
to
wave
attack
and
erosion.
5.
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.
Human
activities
Building
port
facilities
• For
livelihood
and
trading
purposes.
Building
marinas
• Docks
or
yachts
for
recreational
activities.
Tourists
• Tourists
dumping
waste
also
cause
pollution
on
beach
environments.

2. FACTORS
AFFECTING
SIZE
&
WAVE
ENERGY
(generation
of
sea
waves)
[tb
pg
10]:
1.
Wind
speed
• The
faster
the
wind
blows,
the
greater
the
wind
energy
possessed
by
the
waves.
2.
Duration
of
wind
• The
longer
the
wind
blows,
the
larger
the
waves
become.
3.
Fetch*
• The
longer
the
fetch,
the
bigger
the
waves.
Waves:
Waves
are
generated
when
kinetic
energy
is
transferred
from
wind
to
the
water
surface.
(a)
Waves
in
the
OPEN
OCEAN
[tb
pg
11]
(b)
Waves
NEAR
THE
COASTLINE
[tb
pg
11-­‐12]
• Low
wave
height
• Wave
height
increases
• Long
wave
length
• Wave
length
decreases
In
theory,
water
particles
move
in
an
orbit
motion.
• However
in
reality,
water
particles
do
not
make
full
orbits,
thus
objects
move
slightly
forward
in
the
ocean.
As
waves
enter
shallow
water,
they
slow
down,
grow
taller
and
change
shape:
• (1)
At
a
depth
of
half
its
wavelength,
the
rounded
waves
start
to
rise
as
the
waves
interact
with
the
seabed.
• (2)
As
we
go
nearer
the
coastline,
the
base
of
the
wave
experiences
friction
with
the
shallow
seabed.
• Friction
causes
the
base
of
the
wave
to
lose
energy,
and
thus
the
base
of
the
wave
slows
down.
• (3)
The
waves
that
are
slowing
down
are
being
pushed
forward
by
the
waves
behind
them
which
are
moving
faster.

the
waves
in
front
is
thus
forced
to
rise
(steepness
increase).
• (4)
When
the
wave
becomes
too
steep,
it
eventually
collapses
and
breaks
onto
the
beach.
• When
waves
break,
they
release
energy
on
the
coast,
breaking
down
rocks
along
the
coastline
into
smaller
particles.

These
smaller
particles
are
then
subjected
to
coastal
processes
(erosion,
deposition,
transport),
and
are
moved
to
other
parts
of
the
coast.
How
do
waves
affect
coastal
areas?
Process
which
occur
WHEN
WAVES
BREAK
[tb
pg
12]:
(i)
Swash
(ii)
Backwash
• When
waves
break,
water
rushes
up
the
beach.
• This
forward
movement
of
a
wave
onto
the
beach
is
known
as
swash.
• Swash
brings
beach
materials
up
the
beach,
thus
the
beach
gets
built
up
via
the
process
of
sediment
deposition.
• 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.
• Backwash
removes
materials
from
the
beach.

3. How
do
waves
affect
coastal
areas?
(cont’d)
Distinguish
between
DIFFERENT
TYPES
OF
WAVES
and
their
associated
coastal
environments
[tb
pg
12-­‐13]:

Constructive
waves
(spilling/swell)

Destructive
waves
(surging/plunging)
• Constructive
waves
are
low-­‐energy
waves
where
the
swash
is
stronger
than
the
backwash.
• Constructive
waves
break
far
from
the
shore.
• Destructive
waves
are
large,
high-­‐energy
waves
where
the
backwash
is
stronger
than
the
swash.
• High-­‐energy
waves
are
associated
with
storms.
• Strong
swash
deposits
a
lot
of
sediments/material
onto
the
beach.
• Backwash
is
weak
as
the
wave
has
spent
most
of
its
energy
overcoming
friction
with
the
shallow
seabed.

Little
beach
materials
are
removed.
• Thus,
coast
is
built
up
by
deposition
of
sediments.
• The
strong
backwash
transports
rocks
and
beach
material
away
from
the
beach
efficiently.
• The
weak
swash
deposits
lesser
material
than
what
is
being
transported
away.
• Thus,
the
strong
backwash
erodes
coasts
by
removing
beach
materials.
Wave
environments:
• Low
energy
environment
• Low
gradient
(gentle
sloping
beach)
Wave
environments:
• High
energy
environment
• Steep
gradient
(usually
on
a
steep
slope
that
causes
the
waves
to
break)
WAVE
REFRACTION*
[tb
pg
13]:
At
headlands
At
bays
• Waves
tend
to
converge
as
they
approach
headlands.
• Wave
refraction
causes
a
concentration
of
energy
at
the
headlands.
• Greater
erosive
energy
at
headlands
• Increased
wave
height
• Waves
tend
to
diverge
as
they
approach
bays.
• Wave
refraction
causes
energy
to
spread
out
in
the
bays,
leading
to
deposition.
• Reduced
erosive
energy
in
the
bays
• Decreased
wave
height
Different
COASTAL
PROCESSES:

4. Different
COASTAL
PROCESSES
(cont’d)
:
(a)
Coastal
EROSION
[tb
pg
15]:
Process
which
results
in
removal
of
materials
from
a
coast.
 Corrasion
/Abrasion
• The
waves
throw
rock
particles
at
the
coast
and
these
rock
particles
knock
and
scrape
against
the
coastal
cliffs,
eroding
the
cliff
face
away.
 Attrition
• Rocks
and
pebbles
collide
with
each
other,
breaking
down
into
smaller
and
more
rounded
pieces.
 Solution
/
Corrosion
• Acids
contained
in
seawater
will
slowly
dissolve
rock
minerals
(eg.
limestone
rocks
are
easily
dissolved
by
carbonic
acid).
 Hydraulic
action
• The
force
of
the
waves
compresses
the
air
found
in
cracks
in
the
rocks,
creating
tremendous
pressure
along
the
joints
of
surrounding
rocks.
• Eventually,
the
rocks
are
forced
apart.
(b)
Sediment
DEPOSITION
[tb
pg
18]:
Process
which
results
in
materials
being
added
to
a
coast.
 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.
 Depends
on
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.
 Depends
on
location
and
type
of
coast:
• Deposition
occurs
on
gently
sloping
beaches
and
sheltered
coasts.
(c)
Sediment
TRANSPORTATION*
[tb
pg
16]:
Process
where
materials
are
moved
along
the
coast.
 Sediments
are
transported
along
coasts
through
two
related
processes:
• (i)
Beach
Drift
− As
waves
approach
the
coast
at
an
angle,
sediments
move
up
the
beach
at
an
angle
as
swash
(AB).
− It
then
moves
perpendicularly
down
the
beach
(BC)
as
backwash.
• (ii)
Longshore
Currents
− As
waves
approach
the
coast
at
an
angle,
they
generate
longshore
currents
in
the
nearshore
zone,
thus
moving
and
transporting
materials
along
the
shore.
− These
currents
flows
parallel
to
the
coast.
 The
processes
of
beach
drift
and
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.

5.
Definitions*:
Coast
A
zone
where
the
land
meets
and
interacts
with
the
sea.
Fetch
The
distance
over
which
winds
blows
across
open
water
to
form
waves
Wave
refraction
The
process
by
which
waves
change
direction
as
they
approach
the
coast.
Different
coastal
environments
give
rise
to
a
variety
of
COASTAL
LANDFORMS
[tb
pg
20-­‐28]:
• Describe
and
explain
the
formation
of
the
different
coastal
landforms.
• Identify
coastal
landforms
and
features
shown
in
photographs
and
maps.

7. How
can
coastal
areas
be
managed?
• Coastal
areas
should
be
managed
in
a
sustainable
manner:
• Sustainable
means
that
development
should
not
compromise
the
quality
of
the
environment
for
present
and
future
generations.
• Measures
should
be
put
in
place
so
that
little
or
no
deterioration
should
occur
after
beach
restoration.
Management
of
coastal
areas:
• Limit
damaging
activities
• Protect
coastal
resources
• Restrict
development
in
areas
prone
to
natural
hazards
(eg
tsunamis
and
flooding)
COASTAL
PROTECTION
MEASURES:
(a)
Soft
engineering
(b)
Hard
engineering
• Involves
protecting
the
coast
using
natural
processes.
• Involves
the
construction
of
physical
structures
to
protect
coast
against
the
erosive
power
of
waves.
• Evaluate
the
effectiveness
of
coastal
protection
measures.
• Able
to
identify
engineering
measures
adopted
to
mitigate
coastal
erosion
shown
in
photographs
and
sketches.
• A
case
study
of
Singapore.