Rivers Flashcards

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1
Q

What is the course of a river?

A

The downhill flow of the river

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2
Q

What are the characteristics of the Upper Course?

A

Steep, V shaped Valley, Deep channel, Narrow Channel

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3
Q

What are the characteristics of the Upper Course?

A

Medium Gradient, Sloping Sides, Widening deepening channel

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4
Q

What are the characteristics of the Lower Course?

A

Wide channel, flat valley, deep channel

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5
Q

What is vertical erosion?

A

Deepens the valley and channel, scraping angular erosion

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6
Q

What is lateral erosion?

A

Widens the valley and channel, forms meanders

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7
Q

What is Hydraulic Action?

A

The force of the river colliding with rocks to break them

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8
Q

What is Abrasion?

A

Eroded rocks are picked up by the river and scrape against the channel

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9
Q

What is attrition?

A

Rocks crash into eachother, shattering into smaller fragments, the rocks round off

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10
Q

What is solution?

A

When rock is dissolved by river water

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11
Q

What is Traction?

A

When large boulders are forced across the river bed by water

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12
Q

What is saltation?

A

Pebbles are bounced off the river bed

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13
Q

What is suspension?

A

When small particles are suspended in water and carried by it

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14
Q

What is solution?

A

When materials are dissolved in water

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15
Q

What factors cause deposition?

A
  • Water losing energy
  • The volume of water falls
  • There’s more eroded material and the water can’t carry it
  • The water gets shallower
  • The river reaches its mouth
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16
Q

How is a waterfall formed?

A
  • Water flows over hard and soft rock
  • Soft rock erodes by abrasion
  • Creates a step
  • Water flows over the step
  • The waterfall undercuts the area under the step
  • This causes the step to collapse
  • The step falls and is swirled under the waterfall
  • This erodes into a plunge pool
  • Repeat! Causing Retreat
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17
Q

How do meanders form?

A

Faster currents on the outer bend, erode the outside bend

Small River Cliffs form at the bends

Since current is stronger inside, material is deposited on the outside of the bend

A slip off slope makes the inside bend shallower and the outside deeper

18
Q

How are oxbow lakes formed?

A

Meanders continue to widen

The neck gets closer and closer until it breaks through

The river takes the shortest course and doesn’t carry sediment into the meander because there’s not enough energy

Deposition occurs and closes off the meander

19
Q

What are levees?

A

Natural embankments along the edges

20
Q

Why do we get levees?

A

The river floods and rises over the channel

The heaviest material is deposited at the edges of the channel

Deposited Material creates levels

21
Q

What is a Floodplain?

A

The valley floor around the sides of a river where flooding occasionally occurs\

Material builds up here due to deposition

22
Q

What are the 4 types of Soft Engineering?

A
  • Warnings
  • Zoning
  • Tree Planting
  • River Restoration
23
Q

What do Warnings do?

A

Alerts through TV, Radio and Mobile Phones

24
Q

Warnings: Negatives

A

Doesn’t prevent flooding, may give a false sense of security

25
Q

Warnings: Positive

A

Allow for planning and preparedness, moving possessions etc.

26
Q

What is flood plain zoning?

A

Refraining from building on parts of a flood plain

27
Q

Zoning: Positives

A

Fewer impermeable surfaces are created

No Buildings to damage

28
Q

Zoning: Negatives

A

Not helpful in already developed areas.

Limited expansion of urban areas

29
Q

What is tree planting?

A

Increasing interception and lag time

30
Q

Tree Planting: Benefits

A

Discharge and flood risk decrease

31
Q

Tree Planting: Negatives

A

Reduces land that can be used for agriculture

32
Q

What is river restoration?

A

Making the river more natural, allowing the floodplain to flood naturally

33
Q

Restoration: Positiives

A

Less Maintainance required

Less risk of flooding downstream

34
Q

Restoration: Negatives

A

Local flood risk increases

35
Q

What are the 4 Hard engineering tactics?

A

Dams and Reservoirs
Channel Straightening
Embankments
Flood Relief Channels

36
Q

What are Dams?

A

Artificial lakes form behind a large dam in the upper course

37
Q

What is channel straightening?

A

Meanders are removed, making channels straighter

38
Q

What are the positives and negatives of channel straightening?

A

P: Water leaves the area quickly

N: Faster moving water may cause erosion downstream.

39
Q

What are Embankments?

A

Raised walls along river banks

40
Q

What are Embankment Positives and Negatives?

A

P: The river can hold more water

N: Severe flooding may occur if the embankments break

41
Q

What are flood relief channels?

A

Channels are built to divert water around built up areas to divert water

42
Q

What are flood relief channels positives and negatives?

A

P: The release of water can be controlled

N: Increased discharge occurs where the channels meet the river, causing flooding