River Flow and Landforms Flashcards Preview

Physical Geography A-level > River Flow and Landforms > Flashcards

Flashcards in River Flow and Landforms Deck (28)
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1
Q

Three main types of flow:

A
  • laminar
  • turbulent
  • helicoidal
2
Q

Laminar flow is the flow of water in…

A

sheets, parallel to the channel bed, with no uniform velocity. A smooth and straight and shallow channel is needed. Usually in the lower course of the river.

3
Q

Turbulent flow occurs where…

A

there are high velocities and eddies caused by alternating pools and riffles.

4
Q

Bed roughness also increases…

A

the turbulence, e.g. mountain streams have more than alluvial channels.

5
Q

Turbulent flow is associated with…

A

hydraulic action as turbulences cause variations in pressure within the water.

6
Q

Helicoidal flow is created by…

A

horizontal turbulence, creating a corkscrewing motion. It is associated with meandering river channel.

7
Q

The erosion and deposition by helicoidal flow…

A

creates meanders. Thalweg travels from the outside bank to the outside of the meander.

8
Q

Sinuosity is…

A

the length of a stream channel expressed as a ratio of the valley length.

9
Q

Low sinuosity has value…

A

1 which is straight.

10
Q

Straight channels have sinuosity less than…

A

1.5

11
Q

Meandering channels have greater than…

A

1.5

12
Q

The braided channel is…

A

divided by islands or bars. Islands are vegetated and long-lived bars unvegetated and less stable.

13
Q

Braiding occurs when a stream does not have…

A

the capacity to transport its load in a single channel, the discharge varies and the banks are easily erodible.

14
Q

Meanders are formed because the river tries to achieve…

A

an equilibrium, so energy is equally distributed.

15
Q

River cliffs are…

A

created on the outside of the meander.

16
Q

The meanders may migrate…

A

downstream or laterally(sideways) and erode the floodplain.

17
Q

Incised meanders are meanders that are…

A

well developed on horizontally bedded rocks and forms when a river cuts through alluvium and into the underlying bedrock.

18
Q

Intrenched meanders are…

A

symmetrical and occur when down-cutting is fast enough to offset the lateral erosion.

19
Q

Ingrown meander is a result of…

A

lateral migration. They are asymmetric in cross-section.

20
Q

Variation in the cross-

A

section of the river causes variation in erosion and deposition. Rise to river cliffs on the outside and point bars on the inner bank.

21
Q

Pools and riffles are formed by…

A

turbulence.

22
Q

Eddies(viri) cause deposition of…

A

coarse sediment forming riffles and fine fine sediment forming pools.

23
Q

Riffles have…

A

stepper gradient than pools and are located where the river velocity is reduced midstream, in between pools.

24
Q

Levees and floodplain forms where…

A

the river exceeds its banks regularly.

25
Q

The alluvium is carried further and deposited on…

A

on the flood plain.

26
Q

Terraces are formed as…

A

the old floodplains are eroded.

27
Q

River bluffs are the edges of…

A

terrace and it is a line of relatively steep slopes.

28
Q

Two types of incised meanders:

A
  • entrenched

- ingrown