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Geography > Rivers > Flashcards

Rivers Flashcards

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1
Q

What is weathering?

A

Weathering is the breakdown and decay of rock by natural processes.

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2
Q

Name the three types of weathering.

A
  1. Physical (freeze thaw)
    2.Chemical (acid rain)
  2. Biological
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3
Q

What is freeze thaw?

A

Freeze thaw is when water enters crack and the water freezes expanding the crack eventually causing rocks to break into smaller pieces

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4
Q

What is acid rain?

A

All rain is slightly acidic

  • If the air is polluted it makes the rain more acidic
  • The acid rain reacts with weaker minerals causing it to dissolve or decay
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5
Q

What is biological weathering?

A

When roots grow into cracks of rocks causing rocks to split apart.

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6
Q

What is mass movement?

A

The downslope movement of material due to gravity.

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7
Q

Name 2 types of mass movement.

A
  1. Soil creep

2.Slumping

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8
Q

What is soil creep?

A

Where individual particles of soil move slowly down a slope due to gravity and collect at the bottom of valley sides.

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9
Q

What is slumping?

A

When bottom of valley side is eroded by a river.

  • The material becomes steeper.

-The material above slides downwards rotating as it does so.

-Often triggered by periods of heavy rain.

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10
Q

Name 3 MAIN processes that affect a rivers landscape.

A
  1. Weathering
  2. Mass movement
  3. River erosion
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11
Q

Name the 4 types of erosion.

A
  1. Hydraulic action
    2.Abrasion
    3.Solution
    4.Attrition
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12
Q

What is hydraulic action?

A

When the sheer force of water hits the river bed, and banks, wearing them away.

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13
Q

What is abrasion?

A

This is caused by material carried in the river rubbing against the bed and banks of the channel, wearing them away.

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14
Q

What is solution?

A

River water is slightly acidic so it can dissolve some rocks and minerals in contact with the river.

  • Limestone and chalk mostly affected
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15
Q

What is attrition?

A

Sediment particles carried in the river collide with each other

  • This causes the edges to be knocked off. The continued collision of particles in the river causes them to become rounder and smaller downstream.
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16
Q

What are the 4 types of deposition?

A
  1. Traction
  2. Saltation
  3. Suspension
  4. Solution
17
Q

What is traction?

A

Stones roll along the river bed in the direction of the rivers flow.

18
Q

What is saltation?

A

Particles the size of sand grains bounce over each other along the river bed.

19
Q

What is suspension?

A

The water flow carries silt and clay sized particles.

20
Q

What is solution?

A

The river water dissolves some minerals.

21
Q

What are interlocking spurs?

A
  • Near the source
  • Spurs are left interlocking with those from one side of the valley overlapping with the spurs from the other side.
22
Q

How is a waterfall formed?

A
  • When a more hard rock lies over soft rock.

-. River erodes soft rock causing gradually undercutting the hard rock.

  • Continued erosion of soft rock causes an overhang of hard rock
  • Eventually hard rock cant support its weight and collapses due to gravity.

-Erosion of water and large boulders leads to the erosion of the river bed and forms a plunge pool.

  • As soft rock continues to erode the hard rock collapses, a steep sided gorge is formed.
23
Q

What are meanders?

A

Meanders are bends in a river course, commonly found on a river’s flood plain.

24
Q

How are meanders formed?

A
  • As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
  • The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
25
Q

How is an oxbow lake formed?

A
  • Neck becomes narrower. Eventually the river will erode through the neck.

-Water flows through the straight route of the eroded neck.

-Deposition at the neck seals of the bend

  • Gradually begins to dry forming an oxbow lake
26
Q

What are flood plains?

A

Flood plains is the flat area of land either side of a river especially in its lower course.

27
Q

How is a flood plain formed?

A

-It is formed by lateral erosion on the outside bends of meanders.

-Meaning they migrate across the valley floor and can erode valley sides so they become wide and flat.

28
Q

What are Levees?

A

Natural embankments of sediment formed along the banks of rivers that carry a large load and occasionally flood.

29
Q

How are Levees formed?

A

-When it floods, water and sediments come out of the channel as the river overflows its banks.

-River loses velocity and energy and deposits larger and heavy sediments on the banks.

-Repeated flooding causes banks to get higher forming Levees.

30
Q

What are Deltas?

A

When a river reaches another body of water, like an ocean, it loses velocity and deposits sediment.

If the river deposits sediments fast than it can be eroded.

Sediments build up in layers in a fan shaped Deltas.

31
Q

What is a hydrograph?

A

A hydrograph is a way of showing how a river responds to a rainfall event.

32
Q

Why is flood risk in the UK increasing?

A

Increasing population - more people are affected by flooding.

Changes to land use - urbanisation creates more impermeable surfaces and increases surface runoff rates.

Changes to weather patterns - linked to climate change.

33
Q

What are the advantages are disadvantages for having Embankments (Hard Engineering)

Embankments - high banks built on or near river banks

A

Advantages - They stop water from spreading to areas where it can cause problems, for example settlements.

Disadvantages- Flood water may go over the top then get trapped behind them.

They can burst under pressure

34
Q

What are the advantages and disadvantages of flood walls (Hard Engineering)

Flood walls - artificial barriers designed to raise the height of the river banks to hold more water.

A

Advantages - They prevent water from spreading to areas of high impact like housing.

Disadvantages - Expensive to build. They help flood water flow quickly past.

They dont look natural

35
Q

What are the advantages and disadvantages of Demountable flood barriers (Hard engineering)

Demountable flood barriers - a temporary structure that is only installed when needed.

A

Advantages - They can be put up and taken down in areas where flood walls could look ugly.

Disadvantages - Can only be used in the specific location it has been set to be deployed

Risk defence might not be installed in time

36
Q

What are the advantages or disadvantages of flood barriers (Hard engineering)

Flood barriers - floodgates built near the river mouth to prevent storm surge or spring tide from blooding area behind the barrier.

A

Advantages - The gates can be closed when a high tide or surge is forecast.

They are able to protect large areas in storm surge conditions.

Disadvantages - Construction costs are high and need regular maintenance.

37
Q

What are the advantages and disadvantages of flood plain retention (Soft Engineering)

Flood plain retention - strategies to maintain and restore the rivers original land.

A

Advantages - Allowing rivers to flood helps slow flood waters down and recover river’s natural sedimentation processes.

Disadvantage - allowing land to flood may mean a change of land use for example change in farm land.

38
Q

What are the advantages or disadvantages of River restoration (Soft engineering)

River restoration - Using a variety of strategies to restore the river’s original course.

A

Advantages - Allows rivers to flood but slows them down. Natural rivers are more attractive for recreation and create natural habitats.

Disadvantages - Some flood banks often still are needed.

Changes in land use may bring some disadvantage.

Geography (7 decks)

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