1. Coastal Process Description
The greater the difference in air
pressure, the greater the wind
Wind energy
speed leading to greater wind
energy and the larger the waves.
Factors affecting
The greater the fetch or distance
size of waves
Fetch over which the wind blows over
the sea, the larger the waves.
Other Tsunamis, sea traffic can cause
factors the waves to be larger.
1. As a wave approaches the
coast, the height between the
crest of the waves and the
seabed decrease.
2. More friction is exerted and
more energy is dissipated.
3. Speed of waves (in front)
Swash - decrease but speed of waves (be-
hind) are at same speed.
Erosion 4. This pushes the front wave
forward, forcing it to rise.
5. As height of wave increases,
its gradient becomes steeper.
6. It will then collapse and break
onto the beach as swash.
1. Due to gravity, water that has
crashed onto the coast returns
Backwash -
back to the sea perpendicularly
to the coast.
Swash > Backwash
Occurs at gentle coasts.
Constructive
Erosion < Deposition, period is
large, 6-7 waves/min.
Types of waves
Swash < Backwash
Occurs at steep coasts.
Destructive
Erosion > Deposition, period is
small, 10-14 waves/min.

2. Coastal Process Description
Waves tend to approach
the coast at an angle,
depending on prevailing
wind direction.
Swash carries sediments
up on-to the coast at that
angle.
Backwash carries
sediments back to the
sea at a right angle due
Transportation Longshore drift - to gravity.
This motion is repeated
as a zig-zag movement
of sediments along the
coast.
The movement of
sediments parallel to
the coast is known as
longshore drift, which
may be expedited by
longshore currents.
Constructive waves
carry out more
deposition than erosion.
Deposition - - Shallow seabed
increases friction and
wave has less energy
hence it has a weak
backwash.

3. Formation of headlands and bays
Some coasts are made of alternate strips of hard and resistant rocks and less resistant rocks. They
are arranged at right angles to the coast. Due to the different resistance, different rates of erosion
will occur where the less resistant rock is eroded more than the resistant rock. This will form
indented coasts with headlands and bays.
WAVE REFRACTION:
Waves that usually approach the shore in a parallel manner are now refracted or bent as they
approach a headland. Due to the uneven depth of the sea floor, waves bend and and their energy
is distributed unevenly along the shore line.
Formation of beaches
As a result of wave refraction, waves approach the shallow sea in front of the headlands first. As
energy tends to concentrate and strike at the headlands rather than the bays, erosion takes place at
the protruding headlands. Along the bays, waves are diverged and their energy spread out and
weaken. Deposition of sediments thus happen along bays and over time, sandy beaches are
formed.
Formation of cliffs and shore platforms
Repeated poundings of waves against a rocky surface undercuts it. Through erosional processes
such as hydraulic action and abrasion, rocks are weakened. Lines of weaknesses are formed in the
rock face. Over time, the waves will erode the coasts to cut a notch along the lines of weaknesses.
The notch may be further deepened inwards to form a cave. The overhanging part of the notch or
cave eventually collapses with repeated poundings of the waves. As the process continues, an
overhanging cliff is formed. This overhanging cliff will soon collapse and the materials would be
deposited at the foot of the cliff.

4. Some of the materials may be washed away but some of them are picked up by the waves and are
thrown against the base of the cliff resulting in further erosion which causes the cliff to retreat
further inland. A gently-sloping platform called the shore platform appears at the base where the
cliff use to be.
Formation of spits
Longshore currents transport sediments parallel to the coast. When longshore currents encounter
a bay or a bend in the coast with shallow sheltered water, they lose their energy. Materials are
deposited in the direction of the longshore drift. Over time, the accumulation of materials will
appear above the surface forming a narrow, long ridge of sand called a spit where one end is
attached to a mainland while the other extend seawards, it may curve due to changes in wind
direction.
Formation of tombolos
As it extends seawards, it might join up with another offshore island, forming a tombolo. A
tombolo may also join 2 islands.

5. Type of
Method Description + - Example
method
Concrete, Absorbs Very expen- The world’s
rocks or wood energy so that sive to largest seawall
walls built in coast is not construct and in Japan
front of a cliff eroded away, maintain, costing $1.5 bil
or along the protected from LDCs cannot to construct but
Seawalls
coast to absorb strong waves. afford such it failed to
energy protection. protect the
nuclear plants
from the 2011
tsunami.
Granite struc- Deposition Very little of In Singapore,
tures built occurs in the the coast is they are built
parallel to the shallow and protected along ECP as
Breakwaters coast to create calm water, hence there well as Siloso
a zone of forming would be more Beach, Sentosa
shallow and beaches. erosion than and each costs
Hard calm water. deposition. S$1 mil.
Low wall built Allows On the other
at right angles transported side of the
to the coast to materials to groyne, beach
prevent accumulate on is not repleni-
Groynes materials from side of groyne shed and it -
being transp- facing LSD. continues to be
orted away by eroded away.
LSD.
Wire cages Absorbs Rusts easily
containing energy so that and hence the
small rocks to coast is not rocks will fall
Gabions -
form wall. eroded away, out and it will
protected from not work.
strong waves.
Adding large Ensures that Very expen- Cost of beach
amounts of beach is not sive as beach
nourishment to
sand to an eroded away quality sand is
replenish 24km
eroded beach. completely very expensive
of Miami
When LSD, until there is no and replenish-
Beach Beach, USA
Soft transports sand sand left in ing sand must
nourishment costed US$64
away, people some parts of be done every
mil.
bring in sand the beach. 10 years.
from other
places to
replace it.

6. Mangroves Reduces Young mang- Malaysia
have prop or erosion hence roves are very launched a
kneed roots protecting the fragile and project to line
that anchor coast from requires co- 4800km of its
the trees firm- excessive operation of coastline with
Planting ly in the mud- erosion. local people in mangroves
mangroves dy soil, roots the area (eg. after realising
also bind the farmers not to that it protect-
loose soil. let goats feed) ed them during
the 2004
Indian Ocean
Tsunami.
A ridge of Acts as barr- Dunes are
sand piled up iers along fragile and
by wind on the coast to protect vehicular or
Stabilising coast that is human human move-
-
coastal dunes stabilised by properties ment on it may
vegetation (eg. against erosion cause it to will
spinifex, and flooding. not be allowed.
marram)
No building of Safe for Opposed by In England,
Soft new proper- people as they people who there is a
ties in places do not have to invested on
‘green line
known to be at worry about coastal
policy’ that
risk of coastal their houses properties (eg.
does not allow
erosion. being affected beach resort
Relocation of buildings to be
by coastal owners)
property built beyond
erosion.
the line.
Properties
behind the line
is not protected
or insured.
Coral reefs are Reduces speed Human
Malaysia has
masses of of waves appr- activities like
banned fishing
rock-like oaching coast dynamite fish-
in certain
substances hence most of ing, sand min-
areas, built
called corals the energy ing and land
Growth of waste water
growing in would have reclamation
coral reefs treatment
shallow seas. been lost. destroys coral
facilities to
reefs.
encourage
growth of coral
reefs.