Case study of Typhoon Nargis.( This question shows how the topic of river, coast and natural vegetation can be combined together with development))

Figure 1A
Source:. www.acc-tv.com/images/wjla/news/envna_myanmarcyclone


On 2 May 2008 tropical cyclone Nargis hit the coast of Myanmar and devastated large parts of the low-lying Irrawaddy delta. Winds exceeding 190 kilometres per hour ripped through the Myanmar’s biggest city Yangon for more than ten hours. Homes were flattened, more sturdy structures damaged, trees uprooted and power lines downed. In rural parts of the country up to 95 per cent of homes were wiped off the face of the earth. There was an estimated loss of
146 000 lives.

Figure 1B
Source: www.ifrc.org

1. Figure 1A is a map showing the path of Cyclone Nargis which caused a natural disaster in Myanmar on 2 May 2008. Figure 1B is a short write–up on the aftermath of Cyclone Nargis on the southern coastal areas of Myanmar.


a) (i) Name the natural disaster related to tropical cyclone Nargis that happened to Myanmar.[1]

(ii) What evidence from Figure 1B suggest that the destruction caused by nature, Cyclone Nargis, was severe? [5]

(iii)Suggest 3 other natural causes that could have contributed to the severity of the natural disaster .[3]

b)What are some human activities that are likely to have contributed to the severity of the destruction brought about by Cyclone Nargis. Support your answer with examples.[8]


Suggested Answers
a(i) Name the natural disaster related to tropical cyclone Nargis that happened to Myanmar.[1]

Natural Disaster related to Cyclone Nargis or any tropical storm is FLOOD. ( 1)


(ii) What evidence from Figure 1B suggest that the destruction caused by nature, Cyclone Nargis, was severe? [5]

Evidence from write up pointing to the severity of destruction

· Estimate loss of lives was 146 000

· Flooding of large part of low lying Irrawady delta caused by strong wind pushing the waves inland making the floods more severe because Cyclone Nargis would have deposited a lot of rainwater as all tropical storms do.

· Strong wind tore away homes in Yangon the capital city.

· Rural area 95 % of homes ripped off- millions of people loss their homes

· Trees uprooted showing the strength of the storm

· Power lines fallen could have caused death by electrification of people in the vicinity .

[must infer that large number of people died. Must infer that urban areas tend to have more people of which Yangon is one of the places that the cyclone Nargis Swept through dumping lots of Rainfall..


(iii)Suggest 3 other natural causes that could have contributed to the severity of the natural disaster .[3]

· Melting of snow from the Himalayan mountains caused River Irrawady to swell and flood the banks.

· The floodplains of Irrawady delta are too low-lying resulting in floods whenever there is heavy rain .

· Rivers channel bed has become shallow due to heavy silting.

· Storm surge resulting from the strong storm winds .


b)What are some human activities that are likely to have contributed to the severity of the destruction brought about by Cyclone Nargis. Support your answer with examples.[8]

Clearing of forests

· Satellite pictures of Irrawaddy delta shows that deforestation on a large scale has caused heavy silting of River Irrawaddy and the extension of the delta further out into the Bay of Bengal .(1)

-Deforestation Increase surface runoff when less trees intercept the rainwater in tropical climate. (1)

--Heavy silting of river bed is the result of increased rate of erosion on bare slopes after deforestation. There are no roots to bind the soil on slopes. (1)

-Silting of river beds would mean the riverbed is shallow and hence has less capacity to discharge water into the sea giving rise to flooding when there is a storm surge (1) when strong wind pushes the sea water in inland through the delta region causing severe flooding

· Rapid growth in population and the fertile alluvial soil of Irrawaddy delta have attracted many poor people to settle in the delta region to practice subsistence farming. A delta being flat would have spurred growth of transportation resulting in large migration of people (1) to the delta region.
So when the tropical storm hit the area, more people are
affected as compared to a smaller population.(1)

· Urban development

Myanmar being an LDC would mean there is rapid urbanization because of rural-urban migration.
More roads and concrete pavement would be constructed to cater to heavy human traffic. (1)

Concrete pavement increases surface run off (1) resulting in rainwater flowing into the river channel quicker than a forested area. Result is severe flooding in urban areas

· Enhanced greenhouse effect

-Global warming has increased the intensity of tropical storms in recent years resulting in greater destruction e.g Katrina of 2005 hit Florida and New Orleans in USA.
So is the intensity of Nargis…the most powerful Tropical storm that Myanmar has ever recorded.(1)

-Increased atmospheric temperature has caused greater rate of melting of snow in the Himalayas (1)which is the source of Irrawaddy River. The greater melting of snow means more water in river channel. When the greater volume of water in the channel meets with the storm surge, there is a double whammy. Flooding will be very severe.

Award marks for efforts in explaining processes involved e.g deforestation and erosion, increased surface runoff and silting of rivers.

Award marks for candidate who show application of knowledge of rapid snow melting due to global warming and silting plus the dumping of rain by the storm that have contributed to the severity of storm- a case of nature and man creating this horrendous event.


c) Evaluate the effectiveness of management strategies that can reduce the negative impact of floods.[8]

Strategies in reducing negative impact of floods.

1.Building artificial levées and dykes
Walls of sand, stone and concrete are built along river banks to increase the capacity of the river to hold water.

2.Construction of dams
Dams control the amount of water flowing into the rivers, using gates to hold back or release water.

3.Building control
Maps showing flood-prone areas provide information for developers to ensure that floods would not affect the buildings they construct.

4.Watershed management
Programmes can be implemented to manage the entire watershed by conserving vegetation cover or re-planting trees so as to reduce surface run-off.

5.Flood insurance
Residents in flood-prone areas can have their property insured against flood, so that they can afford to repair their property if floods occur.

6.Monitoring and education
Scientists can use modern technology to monitor weather patterns and warn of floods in advance.
Citizens can be educated on how to react when floods occur.

7.Post-flood management measures
Plans can be made by authorities to evacuate victims when floods occur.
Foreign aid may also be offered to help flood victims.

Level 1 (0-3m)
States/ describes the measures of flood control
Provides no/ brief examples with little details of how effective those measures are in flood control

Level 2 (4-6m)

Candidate gave his judgement statement such as ‘to a certain extent’ and gave reason(s) why he said so.
Provides explanations with 2 details but provides one –sided e.g only hardwares like building of dams, dykes, artificial levees and did not give the software measures like educating people on deforestation impact and what to do in a flood.
Citing of examples like Singapore River that had undergone resectioning to deepen and widen the river channel to increase its capacity to discharge storm water.

Level 3 (7-8m)
Judgement statement and indicating how some strategies are more feasible in Less Developed Countries because of lack of funds to construct or maintain the hardwares like construction of dykes, dams

Provide more than 3 measures and weigh the feasibility of each measure especially in the context of LDCs.

Application of knowledge of how corruption of govt officials can derail flood management by diverting funds meant for such flood management into their own pocket
how poverty can make buying of flood insurance a non feasible measure e.g in LDCS like Myanmar.

Worksheet on River and Coast ( Combination of River and Coasttopic)

1 a. Figure 1A is a graph showing surface runoff into a river channel from an urban area and a forested area.

a(i)Describe the differences in the surface runoff into the river channel from the urban and the forested areas. [4]

(ii)Explain why there is a difference in the surface runoff into the river channel. [6]

b. Account for the different characteristics of a river in its upper and lower course. [7]

Suggested Answers

a(i)Describe the differences in the surface runoff into the river channel from the urban and the forested areas. [4]

Urban area
Description of graph
· The graph shows that the surface runoff into river channel for urban areas is much higher than the runoff in forested areas. (1)
· The graph also shows a shorter time taken for the peak shown representing the discharge into the river channel (1) from the urban areas.

Forested area
Description of graph
· The graph shows that less water is discharged into the river channel from forested area(1)
· The graph also shows the rainwater takes a longer time to reach its peak in the river channel(1)


(ii)Explain why there is a difference in the surface runoff into the river channel. [6]

Urban Area

Explanation of graph

· In an urban area, there will be very high surface runoff and little infiltration into the asphalt and concrete surfaces

· Rain which falls immediately gets channelled into drains and from there into the river. (1)

· There is no interception or absorption because of asphalt and concrete ground (1).

· Rapid rise of water in river channel soon after the rain will likely cause floods.

Rural Area

· Less concrete and more natural vegetation to intercept rain resulting in less surface runoff immediately after the rain.(1)

· Percolation of rainwater into the ground which acts like a sponge would mean water will travel underground and fill up the water table before excess water finds its way back into the river channel somewhere further downstream.

This explains why the forested areas have less surface runoff that goes into the river channel which will cause flood.

b. Account for the different characteristics of a river in its upper and lower course. [7]









1 m for each pairing of description

1 m for each pairing of description

Explanation for the shape and other characteristics

Upper course
· In the upper section of the river, the river water is moving very fast because
· the gradient is steep.(1)
· The rocks that the river carries are very potent in eroding the bed of the river because they act as tools to help chisel the sides and bed of the river .
· More vertical erosion takes place resulting in (1)
· a steep-sided V shape valley and gorges and waterfalls

Lower course
· In the lower section of the river, the river valley acquires a wide V shape because

· the river is moving slowly due to loss of gradient, increase in load in channel and consequent loss of energy

· so more lateral erosion occurs resulting in a broad channel and

· deposition of fine river alluvium takes place resulting in formation of floodplains after several episodes of flooding.Max of 4m—any plausible explanation

Figure 1B shows one coastal management strategy.

Identify the coastal management strategy shown in Figure 1B.
Evaluate the effectiveness of several strategies in coastal protection.

Candidates may include the following :

Groynes
· Constructed at right angles to the coast to encourage deposition of materials transported by longshore drift

· Materials are deposited on the side of the groynes facing longshore drift

· However, groynes deprive the coast further down from receiving fresh supply of materials and hence aggravate erosion of the coast on the opposite side of the groyne that does not face the oncoming longshore drift i.e the downdrift side.

· Need to build a series of groynes to protect the entire stretch of the coast

· Short term protection.

Breakwaters
· Waves are made to break offshore at a distance from the coast causing destructive waves to lose energy

· Create a zone of quiet waters between the breakwaters and the coast

· Waves may deposit sediments to create a beach Over time, they serve to extend the coast seawards in the form of a beach.

· Breakwaters only encourage deposition along the part of the coast that is protected.

· The other parts of the coast that is left unprotected will
deprives the coast further down from receiving fresh
supply of materials

· Need to build a series of breakwaters to protect the entire stretch of coast

Seawalls.

· A seawall is usually made of concrete which absorbs the energy of the waves and protects the coast against strong waves.

· Does not guard against backwash, resulting in base of seawalls being eroded away. Seawalls can collapse over time.

· It is costly to build and maintain a seawall.

Soft engineering
· Plant mangroves along shore. Protect the coast against erosion by strong waves and winds. Roots of mangrove bind loose soil

· Prop roots trap sediments and reduce coastal erosion

· Increased sediment buildup may result in shallower coast – affect port activities

· However, coasts with destructive waves do not support mangroves.

· Planting of marran grass along the beach may help to trap sand .

· However all forms of soft engineering would still require human cooperation in the form of limiting human activities in order for nature to take root.

Candidates at each level will show the following characteristics:

Level 1 (0-3m)

May not refer to a measure or be vague in expression
No place reference or very general references to location
No mention of effectiveness, or simple statements only eg. “it worked”, “it was a lot better”

Level 2 (4-6m)

One or more measures considered

Allow assessment of measures
Brief statements of effectiveness, ‘it stopped erosion taking place,’ or ‘erosion occur less often’

Level 3 (7-8m)

Several measures considered in detail. Both hard and soft engineering methods discussed.

Clear statements of judgement such as ‘ high/ low degree of effectiveness ‘

1(a) Using well-labelled diagrams only, explain how a waterfall and plunge pool is formed. [6]




(b) In managing river discharge, many countries have built dams, like the one in Fig. 1. Discuss the threats they pose to the human and physical environment
in employing such methods. [6]






(c) With reference to Fig. 2B which shows a sketch of the photo in Fig. 2A, explain how features Y and Z are formed by marine processes.[5]



(d) Study Fig. 2B, identify and evaluate suitable measures at the respective
places to protect tourists’ beach at X and the area at Z. [8]








Suggested answers


1 (a) Using well-labelled diagrams only, explain how a waterfall and plungepool is formed. [6]

Diagrams- 2m…..

4-5 diagram s— must show development of waterfall and the deepening of plunge pool

DRAW DIAGS

Waterfall
-sill, More Resistant rocks
-Less Resistant rocks lies downstream
-as river flows downstream
-dominant erosional processes- abrasion
-pebbles and rocks chiseled into the bed of the river
-causes the Less Resistant to erode more than the More Resistant
-changes in gradient of river channel
-steeper after prolong erosion, river flows over the steeper gradient that develop on the river bed
-As the water plunges over the steep gradient formed to the river bed below
-A waterfall is formed
-the sheer force of the water plunging [hydraulic action] over a steep gradient
-and the grinding action from eroded rocks and pebbles that are carried by the river
-leads to the formation of a plunge pool
-abrasion- widens and deepens the pool
-hydraulic action-deepens also
-so at base of waterfall a deep plunge pool forms

(b) In managing river discharge, many countries have built dams, like the one in Fig. 2. Discuss the threats they pose to the human and physical environment in employing such methods. [6]

Human environment

· Financial costs that must be incurred in
o construction of those structure.
o Maintenance of these structures, if not
· Poor maintenance will lead to cracks, which will lead to degeneration due to heavy rainfall and so structures will give way which will lead to the flooding of the lower course of the river
· Recent Earthquake in China, close to 300 dams inspected had cracks
o Huge financial strain to repair all affected dams.
o Dams collapsed, massive number of human deaths, destruction of settlements, farms downstream
· Sediments trapped behind dams
o Decrease in depth, leading to smaller capaityc of reservoir and river.
o Increase chance of flooding during heavy rainfall upstream
· Less food for riverine ecosystem
o Decrease in amount fish, shellfish etc
o Affect fishermen and farmers

Physical ENVIRONMENT
· Downstream deprived of sediments ,and less opportunity for flooding
· Formation of Depositional features such as floodplain, delta would be affected
· Decrease fertility of soil as there is less alluvium
· River dynamics after dam as the downstream is changed
· River has less sediments, therefore greater energy to erode

(c) With reference to Fig. 2b which shows a sketch of the photo in Fig. 2a, explain how features Y and Z are formed by marine processes? [5]

Z - Headland
Y - Bay

· alternating resistant and less resistant rocks
· Adjacent to the coast
· Less Resistant rocks - most erosion which gives rise to bays
· leaving more Resistant rock outcrops as headlands
· now as headlands receives highest energy waves – refraction
· so vulnerable to erosion more than the sheltered bays because wave energy dissipated at the bays which experience low energy waves- accumulation of sand
·
(d) Study Fig. 3b, identify and evaluate suitable measures to protect tourists’ beach at X and the area at Z. [8]

L1 0-3
Describes the suitable measures of breakwater, groynes and beach nourishment.

L2 4-6
Describe effectiveness OR ineffectiveness of 1 measure
Describe effectiveness OR ineffectiveness of 2 measures structures
Assess 3 effectiveness OR 3 ineffectiveness of 3 measures
OR
Assess all effectiveness AND ineffectiveness 3 measures with no refernce to
corresponding places—max 4

L3 7-8
Assess all effectiveness AND ineffectiveness of 1 measure and briefly for 2nd .
Assess all effectiveness AND ineffectiveness of 2 measures and briefly for 3rd
structure.
Assess all effectiveness AND ineffectiveness 3 measures

At Z…. Breakwater
- an artificial reef mage of cement or rocks
- built // to coast at some distance from the sea
- just in front of the headland

Function/Advantages
• Break force of waves at some distance from coast
• Creating a zone of quiet water, energy, deposition of materials behind break-water is slack

Disadvantages
1. costly to build and maintain
2. costly US$1m
3. breakwater can be unsightly, spoil scenery of beach. adds to the cost.


At X… Groynes and beach nourishment

Groynes
• Built perpendicular to coast

Function/advantages
• Stop movement of material from coast
• Interrupts Long Shore Drift
• Deposition on side of groyne facing Long Shore Drift -updrift side
• Widens the beach

BUT/disadvatages

• Erosion on the other side-downdrift side
Without regular maintenance of groyne systems they degrade and can become dysfunctional
· Spoils the natural beauty of the area
Tourists activities can be disrupted as this is a tourist beach


Beach nourishment

Advantages
• Simply means sand / beach replenishment
• i.e. rebuilding beaches
• Instant beaches
• Overnight beach

Disadvantages
• Very nice in the beginning
• Very expensive too
• US$1m to 6m per mile
• Temporary measure
• Erodes 10 time faster than natural beach
Lifespan of 10 years to 2 months

1. (a) Figure 1 shows an aerial view of a river. Name and describe the features labelled “X” and “Y”. [2]




(b) Figure 2 shows sketch diagrams of the formation of a river landform Z in the upper course of a river. Identify the river landform Z and describe how the feature is formed. [6]








(c) Describe the problem faced by people living near floodplains and suggest why they do not want to move away. [3]


(d) Name three coastal features that are formed by the erosion of large waves. [3]



(e) Spits and Tombolos (Figure 3) are depositional features found in certain coastal areas with low energy waves.




Describe and explain how they are formed. [5]





(f) To what extent are hard engineering methods such as seawalls and groynes useful in preventing wave erosion along the coasts? [6] (Refer to the notes on beach management that I have posted earlier on)

Suggested answers

1. (a) Figure 1 shows an aerial view of a river.
Name the features labelled “X” and “Y”. [2]
X = Ox bow lake, Y = Meander

(b) Figure 2 shows sketch diagrams of the formation of a river landform Z in the upper course of a river.
Identify the river landform Z and describe how the feature is formed. [6]

1. River landform Z is a waterfall.
2. A river flows across rocks of different resistance.
3. The river erodes the less resistant rock more rapidly
4. And this causes a change in the gradient of the river course.
5. Over time the river plunges from a great height
6. To hit the river bed below with tremendous force.
7. Repeated pounding of the river bed may leave a depression at the base of the waterfall (creating a plunge pool)

(c) Describe the problem faced by people living near floodplains and suggest why they do not want to move. [3]
1. They face the problems of flooding when the river overflows.
2. They do not want to move as the soil is very fertile / good for growing crops
3. This fertility is renewed every year when the river floods.

(d) Name three coastal features that are formed by the erosion of large waves.
[3]
Any 3 of the following:
Arch, stack, stump, cliffs, headlands, bays and wave-cut platforms

(e) Spits and Tombolos (Figure 3) are depositional features found in certain coastal areas with low energy waves.
Describe and explain how they are formed. [5]
1. A spit is formed when longshore currents encounter a bay or a bend in the coast with shallow sheltered water
2. And materials they carry will be deposited,
3. Resulting in a long narrow ridge of sand with one end attached to the mainland over time.
4. Tombolos are created when spits continue to extend seaward and
5. Sediments accumulate between the mainland and an island to join them together.




(f) To what extent are hard engineering methods such as seawalls and groynes useful in preventing wave erosion along the coasts? [6]


Level 1

No supported usefulness or using simple statement.
Eg. Hard engineering methods are useful.

Award 1m for the above and an additional mark for any supporting details.

Level 2

Describes one or more hard enginnering coastal protection scheme(s).
Brief statements of usefulness.

Eg.
Ø To protect a coast from erosion, people have built seawalls in front of a cliff or along the coast.
Ø A sea wall is usually made of concrete, which absorbs the energy of the waves and protects the coast against strong waves, especially during storms.
Ø Therefore, it stops the waves from rushing onto the beach and successfully helps to prevent wave erosion.

Award 3m for describe one method and an additional mark for any further supporting details to explain its usefulness.

Level 3

L2 + Explains the usefulness AND non usefulness of the coastal protection methods.
Clear statements of degree of effectiveness.

Eg.
Ø To protect a coast from erosion, people have built seawalls in front of a cliff or along the coast.
Ø A seawall is usually made of concrete, which absorbs the energy of the waves and protects the coast against strong waves, especially during storms.
Ø Therefore, it stops the waves from rushing onto the beach and successfully helps to prevent wave erosion.
Ø However, a seawall may not protect a coast from erosion in the long run.
Ø As waves break against the seawall, the energy from the waves is redirected downwards, to the base of the seawall, resulting in a strong backwash.
Ø The backwash wears away the base of the seawall, causing it to weaken and eventually collapse.

Award 5m for a description of a coastal protection method and an explanation of the effectiveness and ineffectiveness in implementing the method and an additional mark for any further supporting details/explanations of other methods to a maximum of 6m.

Coastal Management Techniques

The traditional 'hard' defence is the sea wall.
In the past sea walls were vertical and deflected the energy of the waves away from the coast.
In doing so, however, they suffered a lot of expensive damage in a short period of time.

Modern sea walls have a slope and curved top which breaks up the energy of the wave and prevents water going over the top of the wall during heavy storms. Sea walls are very expensive (£2000-£5000 per metre) but should last 20-30 years.




A breakwater is often used to protect a harbour but may be used to protect a stretch of coastline. They are usually made of concrete or blocks of stone but recent cheaper alternative suggestions have included oil drums and used tyres. They have to be strong enough to take the full force of the waves. Since they have to be built in deep water they are, like sea walls, expensive to build.

The best form of natural defence is a beach which efficiently absorbs the energy of the waves. Along many coasts, however, longshore drift causes the beach to thin out in places and erosion of the land behind becomes a problem. Groynes are designed to slow down longshore drift and build up the beach. They are usually made of tropical hardwoods which are more resistant to marine borers and erosion. A few are made of concrete, steel or in more recent times large rocks. They are built at right angles to the shore and spaced about 50-100 metres apart. Groynes may have a life of 15-20 years but often have to be replaced rather than repaired.






A cheaper alternative to sea walls is the revetment (about £1200 per metre). This is a sloping feature which breaks up or absorbs the energy of the waves but may let water and sediment pass through. The older wooden revetment consists of posts fixed into the beach with wooden slats between. Modern revetments have concrete or shaped blocks of stone laid on top of a layer of finer material. Rock armour or riprap consists of layers of very hard rock with the largest, often weighing several tonnes, on the top. Riprap has the advantage of good permeability plus it looks more natural.


The gabion is a metal cage filled with rocks, about 1 metre by 1 metre square. They are stacked to form a simple wall. They are used to protect a cliff or area in the short term only, since they are easily damaged by powerful storm waves and the cages tend to rust quite quickly. Gabions have the advantage of ease of use and are relatively cheap but their life span is short.


Where longshore drift is a serious problem and the supply of beach material is poor, it may be necessary to supplement the natural system by adding lorry loads of sand and shingle to the beach. The natural processes will then spread the material along the coast to help build up the natural defences. This is called beach nourishment. Sometimes dredgers may be anchored offshore and the sediment sprayed on to the beach using high pressure hoses.

Application on Coastal management

Now that you have read the post on coastal management, look at the following pictures.

This set was taken at Changi Ferry Point where we take a bum boat to Pulau Ubin



What are these structure called?

Why are they built?

Recap
The traditional 'hard' defence is the sea wall.
Sea walls were vertical and deflected the energy of the waves away from the coast.

In doing so, however, they suffered a lot of expensive damage in a short period of time.

Sea walls are very expensive but should last 20-30 years.

Do you think this kind of protection is effective?

This set of pictures were taken at the Singapore Sailing Centre

What is this structure called?


Close up view of the structure.


Another view of the structure











Recap
A breakwater is often used to protect a harbour but may be used to protect a stretch of coastline.

They are usually made of concrete or blocks of stone but recent cheaper alternative suggestions have included oil drums and used tyres.

They have to be strong enough to take the full force of the waves.

Since they have to be built in deep water they are, like sea walls, expensive to build.

Access the effectiveness of using breakwater as a form of coastal management.




This set of pictures were taken when I went for the Sce 2 Camp at the camp cantre in East Coast.

What are these structure call?


This is how they are made at the beach.

Notice how a simpel chicken wire mash is made into a box?


Rocks are then filled up and place at the beeach where protection are needed.







Recap
The gabion is a metal cage filled with rocks, about 1 metre by 1 metre square.

They are stacked to form a simple wall.

They are used to protect a cliff or area in the short term only, since they are easily damaged by powerful storm waves and the cages tend to rust quite quickly.

Gabions have the advantage of ease of use and are relatively cheap but their life span is short.

Why do you think we use the gabions instead of sea wall and breakwater here?

Questions on River and Coast

1. (a) Study Figure 1 below which shows a section of coastline in Australia.

Figure 1

(i) Identify the two coastal landforms labelled X and Y in Figure 1. [2]

(ii) With the help of well-labelled diagrams, describe how the landforms above are formed. [6]

(b) Suggest why some parts of a coastline are always hit by powerful waves and how these coasts are able to withstand such powerful waves. [5]

(c) Using Figures 2 and 3, identify Structures A and B and describe how the structures can protect the coast from erosion. [6]
Fig 2

Fig 3

(d) The construction of seawalls is a common coastal protection scheme used by many countries to protect their coastal areas. Discuss the advantages and disadvantages of using a seawall to prevent coastal erosion [6]

Suggested Answers

1. (a) Study Figure 1 below which shows a section of coastline in Australia.
(i) Identify the two coastal landforms labelled X and Y in Figure 1.
X = Headland
Y = Bay

(ii) With the help of well-labelled diagrams, describe how the landforms above are formed. [6]

1. coasts are made up of rocks with different resistance to erosion
2. less resistant rocks are eroded faster than more resistant rocks
3. different rates of erosion produces an uneven coastline
4. less resistant areas of rocks curve inwards as they get eroded away, forming bays
5. areas made of more resistant rocks will protrude out from the coastline, forming headlands
*Award a max of 3m for answers without diagrams.

(b) Suggest why some parts of a coastline are always hit by powerful waves and how these coasts are able to withstand such powerful waves.

1. if the coast faces a very long fetch or a large expanse of ocean, there will be powerful waves.
2. they are able to withstand powerful waves because they are made of hard resistant rocks eg. Granite.
3. it will take a long time to erode such resistant igneous rocks.
4. if the coast is sheltered, there will be few lines of weaknesses.
5. when seawalls and breakwaters are built, wave erosion is reduced too. If there are no strong prevailing winds, wave erosion is reduced too.

(c) Using Figures 2 and 3, identify Structures A and B and describe how the structures can protect the coast from erosion. [6]

1. structure A is a breakwater
2. it is built parallel to the coast but at some distance away to break the force of the incoming waves
3. it creates a zone of sheltered water behind it so that beaches can build up behind it

4. structure B is an artificial coral reef
5. they protect beaches by reducing the speed of the waves approaching the coast
6. thus, by the time the waves reach the shore, most of their energy would have been lost

(d) The construction of seawalls is a common coastal protection scheme used by many countries to protect their coastal areas. Discuss the advantages and disadvantages of using a seawall to prevent coastal erosion. [6]

Level 1 (states advantages and/or disadvantage ) 1-2m
- a seawall is strong and can last long
- it is expensive to construct and maintain

Level 2 (describe one or two advantages OR one or two disadvantages) 3-4m
- a seawall is usually made of granite and is strong enough to protect the coast against strong waves
- as it absorbs the energy of the waves.

Level 3 (describes at least two advantages AND disadvantages) 5-6m
- a seawall is a short-term solution
- as waves break against the seawall, the energy from the waves is redirected downwards at the base of the seawall
- it causes the seawall to weaken and eventually collapse
- it needs careful maintenance and regular repair
- it is expensive to build

Some pictures of sea wall around the world

Question on River and Coast

1. (a) Study the Zambezi River found on the topographical map of Victoria Falls, Zimbabwe (1:25 000) carefully. (apologies for not providing maps)

(i) Identify two major river features shown on the map. (2)
(ii) Using evidence only from the map, explain two important uses of the river to the people living around it. [4]

(b) Figure 1 below shows a sketch of a river valley.

Source:http://www.geographyalltheway.com/ib_geography/ib_drainage_basins/imagesetc/river_profile.jpg
Figure 1

Using the sketch and studies you have made, describe the shape of the river channel and its gradient in the upper and lower course. [4]

(c) Briefly explain how the presence of vegetation affects the volume of water in a river and how roughness of a river channel affects the speed of the river. [6]

(d) (i) Name three measures that may be used in the management of river channels to reduce the problems of flooding. [3]

(ii) Discuss the effectiveness of the measures named in (c)(i) in the control of floods. [6]

Suggest Answer

1. (a) Study the Zambezi River found on the topographical map of Victoria Falls, Zimbabwe (1:25 000) carefully.
(i) Identify two major river features shown on the map. [2]

1. rapids (7613)
2. meanders (7912)
3. waterfall - Rainbow Falls (7918)
4. gorges - Second Gorge (eg 7817 )

(ii) Using evidence only from the map, explain two important uses of the river to the people living around it. [4]

1. tourist attraction
2. eg hotels along the river, network of transport; presence of town/city Victoria Falls Waterfall
3. recreational activities
4. eg chalets along the coast
5. domestic or commercial use
6. eg presence of pump houses (GS7718) to pump water from the river

(b) Figure 1 below shows a sketch of a river valley.
Using the sketch and studies you have made, describe the shape of the river channel and its gradient in the upper and lower course. [4]

1. In the upper course, the river channel tends to be narrow and deep
2. While the gradient is steep
3. In the lower course, the river channel tends to be wide and shallow
4. While the gradient is gentle

(c) Briefly explain how the presence of vegetation affects the volume of water in a river and how roughness of a river channel affects the speed of the river. [6]
Answers that only explain one factor are to be awarded a max of 3m.

Presence of vegetation
1. The presence of thick vegetation in a drainage basin will result in less surface runoff.
2. The vegetation cover intercepts much of the rain that falls and allows some of it to infiltrate into the soil.
3. The increase in infiltration of water also results in a longer lag time for the water to reach the river channel so the volume will be lower.
4. In contrast, in a drainage basin with little or no vegetation, a greater amount of surface runoff occurs as there is no interception of rain and little infiltration into the ground.
5. Therefore, rivers in drainage basins with little or no vegetation cover experience a more rapid increase in the water level.


Roughness of a river channel
6. Increased channel roughness increases the amount of resistance in the river.
7. More energy will be used to overcome the resistance and added friction.
8. The effect is a slowdown in the flow of water.
9. Little obstacles or low channel roughness will have lesser amount of resistance in the river.
10. River flow will be faster as lesser energy is used to overcome the minimal friction by the obstacles.

(d) (i) Name three measures that may be used in the management of river channels to reduce the problems of flooding. [3]

Any 3 of the following:

1. River channelisation / Re-alignment
2. River re-sectioning
3. Bank protection
4. Planting Mangroves
5. Stabilising sand dunes
6. Growing corals

(ii) Discuss the effectiveness of the measures named in (c)(i) in the control of floods. [6]

Level 1 (describe one or two measures, no comment on whether they are effective or not ) 1-2m

- rivers can be deepened using re-sectioning or building bank protection.

Level 2 (describe one or two measures and briefly explain how effective they are in reducing floods) 3-4m

- re-sectioning is done by deepening a river using dredging.
- this is done to prevent the river water from reaching flood height and are generally effective.

Level 3 (describe two or three measures and explain effectiveness clearly with reference to positive and negative effects) 5-6m

- re-alignment helps to straighten the river channel
- it increases the speed of flow which will prevent the water from ever reaching flood height.
- it is an effective long-term measure.
- however, a lot of resources and manpower are required to carry them out.

Question on River and Coast

1(a) The diagram shows differences in the speed of flow of water in a river channel along a straight part of a river’s course (Click to see a bigger picture)

(i) Describe and explain the differences in the speed of flow

A) from the river bank to the middle of the river channel at the surface (from X to Y) [5]

B) from the surface of the river channel to the river bed near the middle of the river (from Y to Z) [4]

(ii) Explain how the speed of flow in a meander channel might differ from that shown in the diagram above and state the resulting features at the meander sides. [6]

(ii) Explain how the speed of flow in a meander channel might differ from that shown in the diagram above and state the resulting features at the meander sides. [6]

1b. Figs A and B show a section of coastline before coastal defences were built and after coastal defences were built.

(i) Describe the coastal section shown in Fig A and explain how it was affected by natural processes. [4]

(ii) Evaluate the success of the coastal defences shown along this section of the coastline as shown in Fig B. [6]

Suggested Answers

Suggested Answers

1(a) The diagram shows differences in the speed of flow of water in a river channel along a straight part of a river’s course.

(i) Describe and explain the differences in the speed of flow

A) from the river bank to the middle of the river channel at the surface (from X to Y) [5]

1. the speed of flow is slowest at the river bank (X)
2. because of friction with the sides
3. the speed of flow becomes faster towards the

middle of the channel (Y)
4. because the channel at the centre is deep
5. so there is less friction

B) from the surface of the river channel to the river bed near the middle of the river (from Y to Z) [4]

1. at Y, which is near the surface of the middle of the
channel, the river flow is fastest
2. as there is no friction
3. on approaching the river bed at Z, the river speed
slows down
4. because there is increasing friction with the river bed

(ii) Explain how the speed of flow in a meander channel might differ from that shown in the diagram above and state the resulting features at the meander sides. [6]

1. in a meander channel, the river bends
2. as the river water flows downstream and round a bend, the
force and hence speed of flow is greatest at the concave
bank (outer bank)
3. this will give rise to river cliffs
4. the force of water is furthest from the convex bank so the
speed of flow is slowest at the convex bank (inner bank)
5. this will give rise to slip-off slopes
6. hence the fastest flow is at the concave bank of a
meander and not in the centre as shown in the diagram above

(b) Figs A and B show a section of coastline before coastal defences were built and after coastal defences were built.

(i) Describe the coastal section shown in Fig A and explain how it was affected by natural processes. [4]

1. in fig A, a landslip has taken place
2. this is because the land has poor drainage due to the layer
of clay
3. the water cannot drain through the layer of clay and so
collects in the soil
4. eventually the weight of the water-logged soil causes it to
slump down

(ii) Evaluate the success of the coastal defences shown along this section of the coastline as shown in Fig B. [6]

Level 1 (briefly describes at least two measures taken without evaluation) 1-2m

- drain is constructed at the point where the layer of clay starts
- steel barrier is placed mid-way up the cliff
- trench filled with rocks is carved out at the foot of the cliff
- concrete posts are placed at the foot of the cliff
- wooden barriers (groynes) are laid at the shoreline

Level 2 (describes at least two in greater detail and attempts to evaluate) 3-4m

- drain is constructed at the point where the layer of clay starts so that it can drain off the water and the soil will not be water-logged
- steel barrier is placed mid-way up the cliff to hold the land back and prevent it from slipping
- trench filled with rocks is carved out at the foot of the cliff so that even if the land slips, the trench will contain it and the rocks will prevent the soil from slipping further (rocks provide resistance)
- concrete posts placed at the foot of the hill hold the soil in place as the posts have to be driven into the soil so they are a stabilizing force
- wooden barriers (groynes) laid at the shoreline slow down erosion from longshore drift so the soil at the bottom of the cliff is not washed away and this will prevent weakening of the base of the cliff

Level 3 (considers broader picture) 5-6m

- the coastal defences are strong and should hold the cliff in place
- but if rainfall is too heavy, there might be some landslip still as gravel and sand are small and loosely-held so they may just be washed down the cliff face, thus causing erosion and slumping