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Geography > River Landscapes in the UK > Flashcards

River Landscapes in the UK Flashcards

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1
Q

What is the gradient like in the upper course?

A

Steep

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2
Q

What is the gradient like in the middle course?

A

Medium

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3
Q

What is the gradient like in the lower course?

A

Gentle

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4
Q

What is the valley [2] and channel shape [2] like in the upper course?

A
  1. V-shaped valley, steep sides
  2. Narrow, shallow channel
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5
Q

What is the valley [1] and channel shape [2] like in the middle course?

A
  1. Gentle sloping valley sides
  2. Wider, deeper channel
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6
Q

What is the valley [2] and channel shape [2] like in the lower course?

A
  1. Very wide, almost flat valley
  2. Very wide, deep channel
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7
Q

What does vertical erosion do?

A

Deepens the river valley and channel, making it v-shaped

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8
Q

Where is lateral erosion dominant?

A

Upper course

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9
Q

How does vertical erosion occur?

A

High turbulence causes the rough, angular particles to be scraped along the river bed, causing intense downwards erosion

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10
Q

What does lateral erosion do?

A

Widens the river valley and channel

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11
Q

Where is lateral erosion dominant?

A

Middle and lower course

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12
Q

What is hydraulic action?

A

The force of the river water colliding with rocks breaks rock particles away from the river channel

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13
Q

What is abrasion?

A

Eroded rocks picked up by the river scrape and rub against the channel, wearing it away

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14
Q

What is attrition?

A

Eroded material is picked up by the river, crash into each other and break into smaller fragments. Their edges also get rounded off as they rub together

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15
Q

What is solution?

A

River water dissolves some types of rock e.g. chalk and limestone

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16
Q

Why do rivers slow down and deposit material? [4]

A
  1. Volume of water falls
  2. Amount of eroded material increases
  3. Water is shallower
  4. River reaches its mouth
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17
Q

Explain how waterfalls are formed [4]

A
  1. Waterfalls form where a river flows over an area of hard rock followed by an area of softer rock
  2. The softer rock is eroded (by hydraulic action and abrasion) more than the hard rock, creating a step in the river
  3. As the water flows over the step it erodes more and more of the softer rock
  4. A steep drop is eventually created, which is called a waterfall
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18
Q

Explain how a waterfall leads to a plunge pool and gorge [6]

A
  1. The hard rock is eventually undercut by erosion
  2. It becomes unsupported and collapses
  3. The collapsed rock is swirled around at the foot of the waterfall, where it erodes the softer rock by abrasion
  4. This creates a deep plunge pool
  5. Over time, more undercutting causes more collapses and the waterfall retreats
  6. This leaves a steep-sided gorge
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19
Q

Explain how interlocking spurs are formed [4]

A
  1. In the upper course of a river, most of the erosion is vertically downwards
  2. This creates steep-sided, v-shaped valleys
  3. The rivers lack the power to erode laterally, so they have to wind around the high hillsides
  4. The hillsides that interlock with each other as the river winds around them are called interlocking spurs
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20
Q

Explain how meanders are formed [4]

A
  1. The current is faster on the outside of the bend because the river channel is deeper (less friction)
  2. So more erosion takes place on the outside bend, forming river cliffs
  3. The current is slower on the inside of the bend because the river channel is shallower (more friction)
  4. So eroded material is deposited on the inside of the bend, forming slip-off slopes
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21
Q

Explain how meanders lead to ox-bow lakes [6]

A
  1. Erosion causes the outside bends to get closer
  2. Until there’s only a small bit of land left between the bends
  3. The river breaks through this land (usually in a flood)
  4. The river flows along the shortest course
  5. Deposition eventually cuts off the meander
  6. Forming an ox-bow lake
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22
Q

How do flood plains build up?

A

When rivers flood, the water slows down, loses energy and deposits the material it’s transporting. This builds up the flood plain

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23
Q

Explain how levees are formed [3]

A
  1. During a flood, eroded material is deposited over the whole flood plain
  2. The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down and loses energy
  3. Over time, the deposited material builds up, creating levees along the edges
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24
Q

Explain how estuaries are formed [4]

A
  1. When water floods over the bank of rivers, it carries silt and sand onto the valley floor
  2. As the tide reaches its highest point, the water moves slowly and has little energy so it deposits sediment
  3. Over time, more mud builds up, creating mud flats
  4. At low tide, these wide, muddy banks are exposed
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25
Q

How does heavy rainfall affect flood risk? [3]

A
  1. Water arrives too quickly to infiltrate
  2. So there is lots of surface runoff
  3. This increases discharge
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26
Q

How does prolonged rainfall affect flood risk? [4]

A
  1. Soil becomes saturated
  2. Further rainfall can’t infiltrate
  3. So runoff is increased
  4. And discharge increases
27
Q

How does geology affect flood risk? [2]

A
  1. Clay soils and other rocks are impermeable
  2. So runoff is increased
28
Q

How does relief affect flood risk? [3]

A
  1. If a river is in a steep-sided valley, water will reach the river channel quicker
  2. This is because it can flow faster down the steep slopes
  3. This increases discharge
29
Q

How does land use affect flood risk (buildings)? [4]

A
  1. Buildings are often made from impermeable materials and surrounded by roads made from impermeable surfaces
  2. This increases surface runoff
  3. Man-made drains then quickly transport runoff to rivers
  4. This increases discharge
30
Q

How does land use affect flood risk (deforestation)? [3]

A
  1. Trees intercept rainwater on their leaves, which then evaporates
  2. Trees also take up a store water from the ground
  3. Therefore, cutting down trees increases the volume of water that enters the river channel
31
Q

What is discharge?

A

The volume of river water flowing per second

32
Q

What is peak discharge?

A

The highest discharge in the period of time you’re looking at

33
Q

What is lag time?

A

The delay between peak rainfall and peak discharge

34
Q

What is rising limb?

A

The increase in river discharge as rainwater flows into a river

35
Q

What is falling limb?

A

The decrease in river discharge as the river returns to its normal level

36
Q

Why does lag time occur on a hydrograph?

A

Most rainwater doesn’t land directly in the river channel. It flows to the channel as surface runoff or through the ground by infiltartion

37
Q

What does a hydrograph show?

A

Shows how the discharge at a certain point in a river changes over time in relation to rainfall

38
Q

What are dams [1] and reservoirs [1]?

A
  1. Dams are barriers built across rivers, usually in the upper course
  2. A reservoir is an artificial lake that is formed behind a dam
39
Q

Benefits of dams [2]

A
  1. Store water, control water flow and prevent flooding downstream
  2. Can also be used to generate hydroelectric power
40
Q

Disadvantages of dams [3]

A
  1. Very expensive to build
  2. Settlements have to be flooded to create a resevoir
  3. Material is deposited in the reservoir, not along the river’s course, so farmland downstream can become less fertile
41
Q

What is channel straightening?

A

Meanders are removed by building straighter, artificial channels

42
Q

Benefits of channel straightening

A

Water leaves the area more quickly rather than building up, so flood risk is lower

43
Q

Disadvantages of channel straightening [2]

A
  1. Flooding may happen downstream instead
  2. Fast-moving water may cause more erosion downstream
44
Q

What are embankments?

A

Raised walls that are built along river banks

45
Q

Benefits of embankments

A

The river can hold more water, so floods are less frequent

46
Q

Disadvantages of embankments [2]

A
  1. Expensive
  2. Risk of severe flooding if they break
47
Q

What are flood relief channels? [2]

A
  1. Channels built to divert water around built-up areas
  2. Channels built to divert excess water if the river gets too high
48
Q

Benefits of flood relief channels

A

Gates on the channels mean that the release of water can be controlled, reducing flood risk

49
Q

Disadvantages of flood relief channels

A

Will be an increased discharge where the relief channel rejoins the river, which could cause flooding in that area

50
Q

Who issues flood warnings [1] and via what [1]?

A
  1. The Environment Agency
  2. TV, radio, social media
51
Q

Benefits of flood warnings [2]

A
  1. Warnings give people time to move possessions upstairs and evacuate
  2. This reduces the impact of flooding
52
Q

Disadvantages of flood warnings [2]

A
  1. Warnings don’t prevent floods
  2. People may not have access to warnings
53
Q

How can people prepare for floods (buildings)? [2]

A
  1. Sandbags
  2. Flood boards
54
Q

Benefits of preparing for floods

A

Reduces the impact of flooding on homes and businesses

55
Q

Disadvantages of preparing for floods

A

Preparation doesn’t guarantee safety from a flood and it could give people a flase sense of security

56
Q

What is flood plane zoning?

A

Restrictions prevent building on parts of a flood plain that are likely to be affected by a flood

57
Q

Benefits of flood plain zoning [2]

A
  1. Flood risk is reduced - fewer impermeable surfaces created
  2. Impact of flooding is reduced - no buildings to damage
58
Q

Disadvantages of flood plain zoning [2]

A
  1. Expansion of urban areas is limited if there aren’t any other suitable building sites
  2. Can’t help areas with existing buildings
59
Q

What does planting trees involve?

A

Planting trees in the river valley to increase interception of rainwater (and lag time)

60
Q

Benefits of planting trees [3]

A
  1. Discharge and flood risk decrease
  2. Vegetation reduces soil erosion
  3. Vegetation provides habitats for wildlife
61
Q

Disadvantages of planting trees

A

Less land available for farming

62
Q

What does river restoration involve?

A

Making the river more natural (e.g. by removing man-made levees) to allow the flood plain to flood naturally

63
Q

Benefits of river restoration [3]

A
  1. Discharge is reduced, so there’s less risk of flooding downstream
  2. Little maintenance is needed
  3. Better habitats for wildlife
64
Q

Disadvantages of river restoration

A

Local flood risk can increase

Geography (7 decks)

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