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.