25
Sec 3 Geography Test
Topic: Coast
Name: _________________________(
Class: Sec 3 ______
)
Date: _____________
Parent’s signature: __________
Write your answers on the writing papers provided.
1a. Study Fig 1A. Describe and explain how the beach materials are sorted out
from the water’s edge towards the land.
[4]
Fig 1A
•
The finer materials are deposited at the water’s edge while the coarser ones
are located further up the beach. [Must have this point – describing beach
materials]
•
•
•
Beach is a depositional coastal feature formed by constructive waves
When the swash is stronger than the backwash, coarser materials are carried
further up the beach.
The backwash, being weaker, could only carry finer materials which are
lighter down to the water edge.
1
1b. Study Fig 1B.
Fig 1B
(i) Identify and describe the coastal feature labelled as Y.
•
•
A tombolo (or peninsula)
is a ridge of sand joining the mainland to an island.
(ii) Explain how feature Y could be formed.
•
•
•
•
•
•
[6]
A tombolo is formed by longshore drift.
Longshore drift does not change direction when the coastline bends
abruptly.
Instead, the longshore drift will continue to transport material in its original
direction for some distance.
The material is transported by longshore drift into the sea.
When the deposits are thick enough to rise above the water, they form a
long, narrow, low-lying extension to the land, called a spit.
When a spit increased in length until it joined a nearby island, a tombolo is
formed.
1c. Distinguish between constructive and destructive waves.
[2]
[5]
Constructive waves are small, low waves while destructive waves are
large, high waves.
Constructive waves have longer wave length than destructive waves.
Constructive waves have smaller wave height than destructive waves.
2
Constructive waves hare a less frequent wave period of 6-8 waves
breaking in a minute while destructive waves have a more frequent wave
period of 10-14 waves breaking in a minute.
Constructive waves are common on a gentle coastal slope while
destructive waves are common on a steep coastal slope.
Constructive waves spill over when breaking while destructive waves
plunge over when breaking.
Constructive waves have more powerful swash than backwash while
destructive waves have more powerful backwash than swash
Constructive waves build up coast by deposition while destructive waves
erode coast.
[Any 5 pts]
1d. Using examples, evaluate the success of both hard and soft engineering
measures taken to protect coastlines from erosion.
[8]
Seawalls made of rocks or concrete – do protect features such as roads and
buildings but may need repairing due to constant erosion – as the waves
deflected by the seawall is redirectly downwards to the base, resulting in
erosion of the base of the seawall and eventually the collapse of the seawall.
E.g Changi beach, Singapore
Breakwaters built offshore – take away energy from coast and protect
marinas and harbours. Cost of building breakwaters is expensive and does
not provide protection of the entire coast as areas not protected by
breakwaters will still be eroded. E.g East Coast Park, Singapore
Groynes are usually wooden structure built at right angles to the coast.
Effective in reducing sediments being carried away by longshore drift but
sand may have to be leveled out at regular intervals and unless a series of
groynes are built, beach further down the coast may still be eroded. Building
a series of groynes cause the coastline to be unslightly. E.g Sussex, UK.
Gabions – wire cages containing small rocks and function as a wall to protect
the coast. Wires rust easily and powerful waves during storm could destroy
the gabions easily
Beach nourishment is sand brought in from other areas – does add to the
beach but needs replacing as it is removed by longshore drift. E.g Miami
Beach in USA. But it usually lasts around 10 years only and it needs regular
maintenance and replenishment. Purchasing high quality beach sand is
expensive.
Planting vegetation such as marram grass – that has extensive roots and
holds sand together in an effort to stabilize sand dunes– sand dunes help to
act as a barrier and absorb the impact of waves. Difficult to stabilize sand
dunes if coastal areas are used as recreational development.
Planting mangroves – absorb the impact of waves too. Roots of mangroves
hold sand particles together to prevent erosion. E.g Malaysia’s mangrove
3
planting project to protect 4800 km of its coastline. Local people who lives in
coastal areas need to support mangrove planting exercise.
Encouraging growth of coral reefs – helps to slow down the approaching
waves, reducing wave energy before it reach the coast, thus reducing
erosion. E.g Malaysia. Coral reefs can only thrive in clear waters and water
pollution in many coastal areas discouraged the growth of coral reefs.
Level 1 (0-3 marks)
Names of measures only
No indications of success of measures to protect coasts
No examples given
Level 2 (4-6 marks)
Details of measures
Simple indication of success – ‘measures are successful in preventing coastal
erosion
At least one general example – in Singapore
Level 3 (7-8 marks)
Details of measures; must have at least 2 hard and 2 soft engineering
measures
Specific indication of success, e.g ‘prevent longshore drift from removing
sediments away’
At least one specific example of named measure – breakwaters at East Coast
Park, Singapore
Clear indication of how measures used were successful in named area(s) and
how measures used were less successful in named area(s).
4
25
Sec 3 Geography Test
Topic: Coast
Name: _________________________(
Class: Sec 3 ______
)
Date: _____________
Parent’s signature: __________
Write your answers on the writing papers provided.
1a. Study Fig 1A. Describe and explain how the beach materials are sorted out
from the water’s edge towards the land.
[4]
Fig 1A
•
The finer materials are deposited at the water’s edge while the coarser ones
are located further up the beach. [Must have this point – describing beach
materials]
•
•
•
Beach is a depositional coastal feature formed by constructive waves
When the swash is stronger than the backwash, coarser materials are carried
further up the beach.
The backwash, being weaker, could only carry finer materials which are
lighter down to the water edge.
5
1b. Study Fig 1B.
Fig 1B
(i) Identify and describe the coastal feature labelled as Z.
[3]
Wave-cut platforms
are gentle-sloping coastal land with a cliff behind.
It is strewn with rock debris from the receding cliff.
6
(ii) With the aid of well-labelled diagrams, explain how feature Z could be
formed.
[7]
Diagram – 2 marks
• Notch, cave, collapsed cliff, wave-cut platform
Waves erode, especially along lines of weakness in the rock face to form
a notch.
The notch is undercut and enlarged to form a cave.
When erosion causes the roof of the cave to lose support, it collapses and
a cliff is formed.
Further undercutting at the base of the cliff forms an overhanging portion
which eventually collapses.
As the steep cliff retreats inland, a gently-sloping land stretching out
towards the sea from the base of the cliff, called a wave-cut platform (or
shore-platform) is formed.
1c. Explain the factors which encourage coastal erosion.
[3]
Types of waves – destructive waves tend to erode coastal land as their
backwash is more powerful.
• Position of coast - Exposed coast such as headlands are more prone to be
eroded.
• Nature of rocks – less resistant rocks and rocks with more lines of weakness
are more easily eroded.
• Climate - Strong prevailing onshore winds (winds which blows from the sea)
encourages erosion. Strong winds result in more destructive waves being
formed.
[Any 3 pts]
•
1d. Using examples, evaluate the success of both hard and soft engineering
measures taken to protect coastlines from erosion.
[8]
7