Rivers

Question 1

What the some types of river erosion?

Answer 1

Hydraulic action, abrasion, attrition, solution.

Question 2

What are some types of river transportation?

Answer 2

Traction, saltation, suspension, solution.

Question 3

What factors lead to deposition?

Answer 3

Shallow water, at the rivers mouth, when the volume of water decreases.

Question 4

What are some main features of the upper course?

Answer 4

Source, v-shaped valleys, tributaries, waterfalls.

Question 5

What are some main features of the middle course?

Answer 5

Meanders, ox-bow lakes.

Question 6

What are some main features of the lower course?

Answer 6

Flood plains, levées, deltas, mouth.

Question 7

How is a waterfall formed? (4 steps)

Answer 7

• When a river flows over two different types of rock, it will erode the softer one quicker
• Water is now falling from a height, and erodes deeper.
• Abrasion continues to undercut the hard rock, leaving it unsupported until eventually it breaks off.
• This process will be repeated, causing the waterfall to retreat.

Question 8

How is a v-shaped valley formed? (4 steps)

Answer 8

• The river downcuts into the land due to abrasion.
• The banks are weathered by freeze-thaw weathering.
• Weathered material falls into the channel due to gravity.
• This leaves a v-shaped valley with steep sides and no floodplain.

Question 9

How is a meander formed? (4 steps)

Answer 9

• In the middle course, lateral erosion occurs.
• The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy, forming a river cliff.
• On the inside of the bend, deposition occurs.
• This causes the meander to migrate over time.

Question 10

How is an ox-now lake formed? (5 steps)

Answer 10

• The flow is quicker on the outside of the meander causing erosion.
• The flow is slower on the inside causing deposition.
• Over time, this causes the neck of land between the meanders become closer.
• In times of heavy flow due to flooding, the river has the energy to break its banks and flow over the neck of land, finding the straightest route.
• The flow in the meander loop is now very slow, causing deposition, which cuts off the loop, creating an ox-bow lake.

Question 11

How are floodplains formed? (2 steps)

Answer 11

• When a river floods, it deposits the material it is carrying due to reduced speed.
• Floodplains are these depositions of very fertile soil on either side of the river.

Question 12

How are levées formed? (2 steps)

Answer 12

• When the river floods, the biggest, most coarse material is deposited the closest to the river banks.
• Over time, after repeated flooding, these levees are built up.