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Geography > Rivers 2 > Flashcards

Rivers 2 Flashcards

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1
Q

What can we use to show the relationship between precipitation and discharge?

A

Hydrographs

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2
Q

Discharge

A

the volume of river water flowing per second, measured in cumecs

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3
Q

Why is discharge not measured from 0?

A

Due to base flow

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4
Q

Peak discharge

A

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

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5
Q

Lag time

A

The delay between peak rainfall and peak discharge

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6
Q

Why does lag time happen?

A

Most rainfall doesn’t land directly in a river channel.

It either flows quickly overland (surface runoff) or soaks into the ground (infiltration) .

It then flows slowly underground to the river channel.

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7
Q

Rising limb

A

The increase in river discharge as rainwater flows into the river.

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8
Q

Falling limb

A

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

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9
Q

On a map, a v- shape where contour lines cross the river points where?

A

Uphill to the river’s source.

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10
Q

What are the three main factors that affect flood risk?

A

-precipitation
-geology
-land use

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11
Q

When does flooding occur?

A

When a river exceeds its maximum capacity (‘bank full’)

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12
Q

A shorter lag time means…

A

…peak discharge is higher and flooding is more likely to occur.

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13
Q

Physical factors affecting flood risk

A

-Heavy rainfall
-prolonged rainfall
-geology
-relief

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14
Q

How does heavy rainfall affect flood risk?

A

Heavy rainfall means that water arrives too quickly to infiltrate the ground.

This means an increase in surface runoff, increasing discharge.

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15
Q

How does prolonged rainfall increase flood risk?

A

Prolonged rainfall saturates the soil.

This means that any further rainfall can’t infiltrate.

This means an increase in surface runoff, increasing discharge.

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16
Q

How does geology increase flood risk?

A

Clay soils and some rocks e.g. granite are impermeable.

This means an increase in surface runoff, increasing discharge.

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17
Q

How does relief of the land increase flood risk ?

A

If a river is in a steep sided valley, water will reach the river channel quicker because it can flow faster down the steep slopes.

This rapidly increases discharge.

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18
Q

Relief

A

Changes in land height.

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19
Q

Human factors affecting flood risk

A

-land use
-(man-made drains)
-(removing trees)

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20
Q

How does land use increase flood risk?

A

Buildings are made from impermeable materials (like concrete).

They are often surrounded by roads made from impermeable surfaces (like tarmac).

This means that water cannot infiltrate the ground easily.

This means an increase in surface runoff, increasing discharge.

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21
Q

How do man-made drains increase flood risk?

A

They quickly transport surface runoff to rivers, increasing discharge.

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22
Q

How does removing trees increase flood risk?

A

Trees intercept rainwater on their leaves, which then evaporates.

Trees also take up and store water from the ground.

This means that cutting down trees increases the volume of water that enters the river channel.

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23
Q

Hard engineering

A

Man-made structures built to control the flow of rivers and reduce flooding.

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24
Q

Soft engineering

A

Schemes set up using knowledge of a river and its processes to reduce the risk of flooding.

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25
Q

What is evidence for an upper course waterfall on a map?

A

-The symbol for a cliff (black, blocky lines)

-Close contour lines

-A narrow valley floor

-A narrow river (thin blue line)

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26
Q

What indicates a river is on steep land on a map?

A

If it crosses a lot of contour lines in a short distance.

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27
Q

Lower course evidence on a map.

A

-Nearby land is low (less than 15m)

-The river doesn’t cross any contour lines

-The river meanders across a large flat area (this is the flood plain)

-The river’s wide (a thick blue line)

-Large meanders

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28
Q

If a river doesn’t cross any contour lines, what does this indicate?

A

That it’s very gently sloping.

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29
Q

Hard engineering strategies used to reduce the risk of flooding.

A

-Dams and reservoirs
-Channel straightening
-Embankments
-Flood relief channels

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30
Q

Dams and reservoirs

A

Dams are barriers built across rivers (usually in the upper course).

A reservoir is built behind the dam.

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31
Q

Dams and reservoirs benefits

A

Reservoirs store excess water (e.g. after heavy rainfall).

This means that water flow can be controlled, which prevents flooding downstream.

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32
Q

Dams and reservoirs disadvantages/costs.

(apart from that dams are expensive to build)

A

Material is deposited in the reservoir rather than further along a river’s course.

This means that farmland downstream can become less fertile.

Also, creating a reservoir can flood existing settlements.

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33
Q

Channel straightening.

A

The removal of meanders by building straighter, artificial river channels.

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34
Q

Channel straightening benefits.

A

Water leaves the area more quickly which lowers flood risk.

35
Q

Channel straightening disadvantages/costs.

A

Faster moving water may cause more erosion downstream.

36
Q

Embankments

A

Raised walls built along river banks.

37
Q

Embankments benefits.

A

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

38
Q

Embankments disadvantages/costs.

A

There is a risk of severe flooding if the water rises above the level of the embankments, or if they break.

39
Q

Flood relief channels.

A

Channels built to divert water around built-up areas.

They can also be built to divert excess water if river levels get too high.

40
Q

Flood relief channels benefits

A

Gates can be placed on the channels.

This means that the release of water can be controlled, reducing flood risk.

41
Q

Flood relief channels disadvantages/costs.

A

There will be increased discharge where the relief channel re-joins the river, which could cause flooding in that area.

42
Q

Soft engineering strategies used to reduce the risk of flooding.

A

-Flood warnings and preparation
-Flood plain zoning
-Planting trees
-River restoration

43
Q

What do soft engineering strategies work with?

A

The river’s natural processes.

So, they tend to be more environmentally friendly than hard engineering strategies.

44
Q

Flood warnings

A

The environmental agency can issue flood warnings through various media e.g. TV, radio

44
Q

Flood preparation

A

Buildings are modified to minimise flood damage.

Residents can prepare sand bags and flood boards prior to floods.

45
Q

Flood warnings benefits

A

Warnings give people time to move possessions upstairs, or put sandbags in place, for example.

This reduces the impact of flooding.

People can also evacuate if needed.

46
Q

Flood warnings disadvantages/costs

A

Warnings don’t prevent floods.

People may not have access to warnings.

47
Q

Flood preparation disadvantages/costs

A

Modifying buildings is expensive.

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

48
Q

Flood plain zoning

A

Flood plain zoning can be used to place restrictions on building in certain areas that are at risk of flooding.

49
Q

Flood plain zoning benefits.

A

Fewer impermeable surfaces are created (like tarmac) which reduces the risk of flooding.

The impact of flooding is also reduced as there are no buildings to be damaged.

50
Q

Flood plain zoning disadvantages/costs

A

Limits the expansion of urban areas (particularly if there aren’t any other building sites nearby) and it can’t help in areas with existing buildings.

51
Q

Planting trees.

A

Planting trees in the river valley increases the interception of rainwater (and lag time).

52
Q

Planting trees benefits

A

Discharge and flood risk decrease.

Vegetation reduces soil erosion in the valley and provides wildlife habitats.

53
Q

Planting trees disadvantages/costs.

A

Less land is available for farming.

54
Q

River restoration

A

The process of making a river more natural e.g. by removing man-made levees.

This enables the natural flooding of a flood plain.

55
Q

River restoration benefits

A

-Discharge is reduced.

This means that there is less risk of flooding downstream.

-Little maintenance is needed.

-There are better wildlife habitats

56
Q

River restoration disadvantages/costs.

A

Local flood risk can increase, especially if nothing is done to prevent major flooding.

57
Q

What is our example of a UK flood management scheme?

A

The Somerset Levels and Moors action plan.

(details on extreme weather flashcards).

58
Q

How much has the river Parret and Tone’s capacity increased by since regular dredging started in 2014?

A

40%

59
Q

How many km of river planned to be dredged? (Parret and Tone)

A

8km

60
Q

Why was ‘The Somerset Levels and Moors action plan’ required?

A

The Somerset levels and the Somerset moors form an extensive area of floodplains and marsh.

The area is drained by several rivers, most notably the Parret and the Brue.

Flooding has occurred here naturally for centuries.

As these areas have been developed for farming and settlements, many people are now at risk from extreme flood events.

After extreme flooding in December 2013 to February 2014, something had to be done.

Estimates suggest that 10% of the area was underwater when the flooding was greatest.

61
Q

Social issues of the flood scheme (negative)

A

-Construction may disrupt resident’s lives

-Compulsory purchase orders were sent out to landowners whose land was needed to widen the river channels. Some people did not want to sell their land.

62
Q

How might construction disrupt resident’s lives?

A

e.g. due to noise pollution and large vehicles blocking roads.

63
Q

Social issues of the flood scheme (positive)

A

-Residents will feel more confident that their homes won’t flood.

64
Q

Economic issues of the flood scheme

A

-The scheme is expected to cost around £100 million in total.

-Homes and businesses in Somerset will be better protected, so there’s less risk of expensive damage to property, loss of stock, and rising insurance costs.

65
Q

Environmental issues of the scheme.

A

Will create more hectares of new riverside habitats, improving the areas biodiversity.

Many trees removed (over 500). They will be- replanted, but will take years to grow back. The same goes for rare grassland species.

66
Q

What is our example of a river valley in the UK (to identify its major landforms of erosion and deposition)?

A

The River Tees

67
Q

Describe the location of the River Tees

A

The River Tees is located in North-East England, and flows 137km east from its source in the Pennine hills to its mouth on the North Sea coast.

68
Q

Source of the River Tees

A

North Pennines, in the moorlands of Cumbria.

Land is marshy as annual rainfall here is high and the ‘moorland sponge’ is unable to hold it all.

600m above sea level.

69
Q

Upper course The River Tees

A

-The river flows over hard, impermeable rocks.

-Vertical erosion has formed v-shaped valleys.

-The river channel winds between interlocking spurs.

70
Q

What does Cow Green reservoir control? (upper course)

A

How much water flows downstream.

71
Q

High Force waterfall

A

-The UK’s largest waterfall

-Formed by differential erosion

-Less resistant limestone is eroded more quickly than more resistant dolerite

-By hydraulic action and abrasion

-Upper course of the river tees

72
Q

Middle course River Tees

A

Lateral erosion overtakes vertical erosion in the middle course, evident by winding meanders.

Barnard Castle is located here.

73
Q

Areas in the lower course of the River Tees (east to west)

A

Darlington
Yarm
Middlesborough

74
Q

What is located between Darlington and Yarm?

A

Sockburn meander

75
Q

Meanders in the lower course of The River Tees are…

… have formed in some areas.

A

much larger

ox-bow lakes

76
Q

Evidence of past flooding can be seen where?

A

The lower course of the river Tees, in naturally formed levees.

77
Q

Yarm

A

Here, there is an artificial river channel:

The location of both industry and urban settlements.

78
Q

What kinds of industry are located at Yarm?

A

-NS oil terminals
-Petrol chemical works
-A nuclear power station
-An iron and steel works

79
Q

Why is there a boom in industry at the artificial part of the Tees through Yarm?

A

There is more space, more water, and easier access to the sea.

80
Q

Mouth of the River Tees

A

A large estuary with mudflats and sandbanks.

Located at the North Sea.

81
Q

Describe what the bedload is like in the upper course of the River Tees.

A

-Angular
-The river is powerful so can carry large fragments of rock.

82
Q

Describe what the bedload is like in the middle course of the River Tees.

A

-Rounded by attrition as its been transported down the river

(Rocks chipping away at each other due to the velocity of the water).

83
Q

Describe what the bedload is like in the lower course of the River Tees (at the mouth)

A

-Small because the river only has energy to carry and deposit the finest material

-‘Estuary mud’

Geography (18 decks)

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