2.2: Rivers (Paper 1 and 2)

Question 1

Explain the characteristics of a river upstream: (3)

Answer 1

• Width is lower upstream (1)
• Speed of water flow is lower upstream (1)
• Depth is lower upstream (1)

Question 2

Explain the characteristics of a river downstream: (3)

Answer 2

• Width is higher downstream (1)
• Speed of water flow is higher downstream (1)
• Depth is higher downstream (1)

Question 3

Explain the characteristics of drainage basins: (3)

Answer 3

• Watershed: A ridge or other line of separation between 2 river systems. (1)
• Tributary: A stream or river which joins a larger river. (1)
• Confluence: The point at which 2 rivers meet. (1)

Question 4

Explain the processes which operate in a drainage basin: (10)

• Interception (1)
• Infiltration (2)
• Through flow (1)
• Groundwater flow (2)
• Evaporation (1)
• Overland flow (3)

Answer 4

• Interception: The precipitation that is collected and stored by vegetation (1)
• Infiltration: The movement of water into the soil. (1) The rate at which water enters the soil depends on the intensity of the rainfall, the permeability of the soil and the extent to which it is already saturated with water. (1)
• Throughflow: The downslope movement of water in the subsoil (1)
• Groundwater flow: The movement f water from land to river through rock. (1) It is the slowest form of such water movement an accounts for the constant flow of water in rivers during times of low rainfall. (1)
• Evaporation: The process in whih a liquid turns to a vapour. (1)
• Overland flow: Overland movement of water after a rainfall. (1) It is the fastest way in which water reaches a river. (1) The amount of overland runoff increases with heavy and prolonged rainfall, steep gradients, lack of vegetation cover and saturated or frozen soil. (1)

Question 5

Explain the erosional processes in a river: (6)

• Hydraulic Action (1)
• Abrasion (1)
• Attrition (2)
• Solution (2)

Answer 5

Hydraulic Action: The force of air and water on the sides of rivers and in cracks. (1)

Abrasion: The wearing away of the bed and bank by the load carried by a river. (1)

• Attrition: The wearing away of the load carried by a river. (1) It creates smaller, rounder particles. (1)
• Solution: The removal of chemical ions, especially calcium which cause rocks to dissolve. (1) The chemical load is carried dissolved in the water. (1)

Question 6

Explain the transportation processes in a river: (5)

• Suspension: (1)
• Saltation: (1)
• Solution: (2)
• Traction: (1)

Answer 6

• Suspension: Small partiles are held up by turbulent flow in the river. (1)
• Saltation: Heavier particles are bounced or bumped along the bed of the river. (1)
• Solution: When materials are dissolved in the river water
• Traction: The heaviest material are dragged or rolled along the bed of a river. (1)

Question 7

Explain why deposition occurs in a river: (4)

Answer 7

• Reduced discharge due to a lack of precipitation or abstraction upstream. (1)
• Decreased gradient. (1)
• Slower flow on the inside of a river bend or where the river is shallower. (1)
• When the river enters a sea/ocean or lake. (1)

Question 8

Explain the characteristics of a long profile:

Answer 8

• The source is usually in an upland area. (1)
• The upper course of the river includes areas which are steep with uneven surfaces. (1)
• In the middle course the gradient decreases. (1)
• In the lower section the gradient decreases
  further until it becomes almost flat. (1)

Question 9

Explain the characteristics: of the upper course of a river: (8)

Answer 9

• Shallow (1)
• Steep valley sides (1)
• Narrow (1)
• Low velocity (1)
• Large bedload (1)
• Rough channel bed (1)
• High levels of friction (1)
• Vertical erosion (1)

Question 10

Explain the characteristics of the middle course of a river: (8)

Answer 10

• Deeper than upper course channel (1)
• Gentle valley sides (1)
• Wider than upper course channel (1)
• Greater velocity than upper course channel (1)
• Material in river decreases in size (1)
• Smoother channel bed (1)
• Lower levels of friction than upper course channel. (1)
• Lateral erosion (1)

Question 11

Explain the characteristics of the lower course of a river: (8)

Answer 11

• Deeper than middle course channel. (1)
• Flat floodplains. (1)
• Wider than middle course channel. (1)
• Greater velocity than the middle course channel (apart from as the river enters the mouth) (1)
• Material carried mainly sediment and alluvium. (1)
• Smooth channel bed. (1)
• Lowest friction. (1)
• Deposition is dominant. (1)

Question 12

Explain how a waterfall is formed: (5)

Answer 12

• Hydraulic action and abrasion are the main erosional processes. (1)
• The soft rock erodes quicker, undercutting the hard rock and creating a plunge pool. (1)
• This leads to the development of an overhang of hard rock which eventually over time, collapses. (1)
• The overhang falls into the plunge pool increasing abrasion and making the plunge pool deeper. (1)
• The process then begins again and the waterfall retreats upstream leaving a steep sided gorge. (1)

Question 13

Explain how a pothole is formed: (3)

Answer 13

• River water is swirled in irregularities in the river bed creating vertical eddies. (1)
• Rocks get swept into the small depressions and abrade the hollow. (1)
• The processes continues deepening and enlarging the pothole. (1)

Question 14

Explain how meanders are formed: (6)

Answer 14

• As the water travels through the meander, it travels faster on the outside bend creating erosion through abrasion and hydraulic action. (1)
• This undercuts the river bank and forms a river cliff. (1)
• The water travels slower on the inside bend causing deposition to create a slip-off slope. (1)
• This whole process continues overtime, the deposition on the inside bend and erosion on the outside bend encourage the bend in the river to be more extreme. (1)
• The rivers current will begin to laterally erode the neck of a meander. (1)
• The meanders neck becomes smaller and narrower overtime. (1)

Question 15

Explain how an oxbow lake is formed: (5)

Answer 15

• Continued erosion causes the river to cut through the neck of the meander completely creating a short-cut for the river current. (1)
• Material will then be deposited at the side of the river bank where the former river channel current cut through. (1)
• A new channel becomes more established, due to deposition, so the previous channel begins to dry up. (1)
• The new channel becomes more established, due to deposition, so the previous channel begins to dry up. (1)
• Marsh plants colonizes the former meander. (1)

Question 16

Explain how a delta is formed: (2)

Answer 16

• The water descends from the river and flows down. When it comes to contact with the lake/sea it will lose energy and deposits its material there. (1)
• However, the water wants to escape and drain as fast as possible into the sea or like, this from distributaries to drain the water as fast as it can. (1)

Question 17

Explain how a levee forms: (4)

Answer 17

• During a flood when the water level rises above the banks, the area directly on either side of the bank is the first area where they are going to be exposed to additional friction. (1)
• Large storms and silt are first deposited on the banks due to loss of energy in the river. (1)
• The sediment builds up on the river bank and forms an elevated section on either side. (1)
• This increases the rivers carrying capacity. (1)

Question 18

Explain how a floodplain is formed. (4)

Answer 18

• Floodplains form when there is a flood. (1)
• During a flood, the water deposits heavy material closer to the river which forms levees. (1)
• The smaller sediment is deposited next to the levee in layers. (1)
• This creates a flat floodplain which is fertile due to alluvium. (1)

Question 19

Explain the causes of river flooding: (2)

Answer 19

• If there is a period of heavy, torrential rain leading to high levels of overland flow because the water cannot infiltrate. (1)
• A prolonged period of steady rain which means that the ground becomes saturated leading to high levels of overland flow because the water cannot infiltrate. (1)

Question 20

Explain the effects of bank erosion: (3)

Answer 20

• Houses and infanstructure on river banks are at risk of collapsing due to hydraulic action and abrasion. (1)
• Families will be displaced. (1)
• Loss of farmland and transport routes. (1)

Question 21

Explain the opportunities presented by living near a river: (6)

Answer 21

• A source of drinking water (1)
• Fertile silt for agriculture (1)
• A line of communications and navigation (1)
• A source of power (1)
• Fishing (1)
• Recreation (1)

Question 22

Explain the opportunities presented by living on a floodplain: (4)

Answer 22

• Open space (1)
• Habitat for wildlife (1)
• Fertile land for agriculture
• Opportunities for fishing, hiking and biking. (1)

Question 23

Explain the opportunities presented by living near a delta:

Answer 23

• Fertile land for farming (1)
• Plenty of water for fishing (1)
• Abundant drinking water (1)
• Tourism opportunities. (1)
• Good transport links and trade routes. (1)

Question 24

Explain what can be done to manage the impacts of flooding: (11)

Answer 24

• Building dams or reservoirs to hold back excess water. (1)
• Raising the banks of rivers. (1)
• Dredging the river channel so that it can hold more water. (1)
• Diverting streams and creating new flood relief channels. (1)
• Using sandbags to prevent water getting into houses. (1)
• Building houses on stilts so that water can pass underneath. (1)
• Land use planning: build only on land that is free from flooding. (1)
• Afforestation to increase interception and reduce overland flow. (1)
• Have insurance cover for vulnerable areas and communities. (1)
• Improved forecasting and warning of floods. (1)
• River restoration and allowing rivers to flood naturally. (1)

Question 25

Define the term drainage basin: (1)

Answer 25

The area of land drained by a river and its tributaries. (1)