Rivers

Question 1

Abrasion (or corrasion)

Answer 1

The wearing away of the bed and bank by the load carried by the river.

Question 2

Attrition

Answer 2

The wearing away of the load carried by a river, which creates smaller, rounder particles.

Question 3

Hydraulic action

Answer 3

The force of air and water on the sides of rivers and in cracks.

Question 4

Solution (or corrosion - not be confused with corrasion)

Answer 4

The removal of chemical ions, especially calcium, which causes rocks to dissolve.

Question 5

Suspension

Answer 5

Small particles are held up by turbulent flow in the river.

Question 6

Saltation

Answer 6

Heavier particles are bounced or bumped along the bed of the river.

Question 7

Solution

Answer 7

The chemical load is dissolved in the water.

Question 8

Traction

Answer 8

The heaviest material is dragged or rolled along the bed of the river.

Question 9

Flotation

Answer 9

Leaves and twigs are carried on the surface of the water.

Question 10

Deposition

Answer 10

The river deposits it’s load, heavier particles first, and then smaller, lighter ones later.

Features of deposition include: deltas, levees, slip-off slopes (point bars), oxbow lakes, braided channels and floodplains.

Question 11

Oxbow lake

Answer 11

A meander that is closed off by deposition to form a oxbow lake.

Question 12

Floodplain

Answer 12

An area covered by water when a river floods.

Question 13

Levees

Answer 13

Raised river banks at the edge of a river.

Question 14

Delta

Answer 14

A flat, low-lying deposit of sediment that is found at a river’s mouth.

Question 15

Braided channels

Answer 15

Multi-channels

Question 16

What are some physical causes of floods?

Answer 16

Climatological:
- rain
- ice melt
- snow melt
Part-climatological
- coastal storm surges 
- estuarine interactions between stream flow and tidal    conditions
Other:
- earthquake
- landslide
- dam failure

Question 17

What are some human-related causes of flood/intensifying?

Answer 17

• more rapid discharge in urban area due to impermeable surface and increased number of drainage channels
• urbanisation and urban growth (increase in impermeable surfaces)
• floodplain developments (increasing risk of damage)
• bridges, dams, obstructions
• changes in vegetation cover, e.g. agriculture
• river engineering works, e.g. levees
• human-induced induced climate change