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GCSE Geography > River management > Flashcards

River management Flashcards

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1
Q

Define precipitation

A

Moisture falling from the atmosphere as rain, hail, sleet or snow

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2
Q

Define discharge

A

The quantity of water that passes a given point on a stream or river bank - within a given period of time

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3
Q

More precipitation = More ____

A

More precipitation = More discharge

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4
Q

What is a hydrograph

A

A hydrograph shows how a river responds to a rainfall event.

This helps us to understand discharge patterns of a particular drainage basin

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5
Q

What two graphs are hydrographs made up of

A

Bar chart = Rainfall

Line graph = Discharge

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6
Q

Features of a hydrograph

A

Peak rainfall
Lag time
Rising Limb
Peak discharge
Falling limb
Base flow (normal flow)

x - axis - time (days and hours)
y- axis - discharge in cumecs

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7
Q

What is peak discharge

A

The highest discharge in a given period of time

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8
Q

What is lag time

A

The delay between peak rainfall and peak discharge

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9
Q

What is rising limb

A

The increase in river discharge as rainwater flows into the river

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10
Q

Falling limb -

A

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

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11
Q

What is the base flow

A

The normal flow of a river when its level is being sustained by groundwater

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12
Q

Label a hydrograph

https://www.jkgeography.com/uploads/1/0/8/4/108433405/screen-shot-2018-01-21-at-16-34-56_orig.png

A

https://www.jkgeography.com/uploads/1/0/8/4/108433405/screen-shot-2018-01-21-at-16-24-02_orig.png

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13
Q

Two types of hydrographs

A

‘Slow response’ hydrograph
‘Flashy response’ hydrograph

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14
Q

Explain the features of a slow response hydrograph

A

Slow response = slow flow

Small amount of rainfall in a prolonged amount of time

There is a less steep rising limb as water is taking longer to enter the river channel

The lag time is long as the water is taking a long time to enter the river channel - the peak discharge is lower as water is lost to infiltration and interception

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15
Q

Conditions that would result in a slow hydrograph

A

Areas with permeable materials, vegetation, gently sloping land, unsaturated soil, good drainage

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16
Q

Describe the features of a flashy response hydrograph

A

flashy response aka storm hydrograph = quick flow

Large amount of rainfall in a short period of time

The rising limb is steep because rainfall has occurred in conditions that have caused a lot of surface run off (when the water flows on the surface instead of permeating in the ground). All rainwater rushes to the river at once

The lag time is short as water gets into the channel quickly due to a lot of surface runoff - therefore the time between rainfall and entering the river is short

The peak discharge is also high as the water has gotten into the river quickly and less water is lost -
High peak discharge as there’s lots of water

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17
Q

Conditions which may result in a flashy hydrograph

A

Prolonged rainfall, which results in saturated soil. Therefore more surface runoff -

Clay soil so water cannot infiltrate

Steep valley/hill so water runs down faster - reducing lag time

Little vegetation leads to more surface runoff (less interception)

Urban area with lots of impermeable materials

Poorly farmed land = increased surface runoff

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18
Q

What is flashy response

A

flashy response hydrograph is associated with sudden flooding called ‘flash floods’

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19
Q

What is a slow response

A

normal rainfall event (low flood risk)

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20
Q

State the physical and human factors that affect flood risk

A

Physical
Precipitation (Heavy rainfall, prolonged rainfall)
Geology (rock type)
Relief (changes in land height)

Human - land use

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21
Q

What is flooding

A

Flooding occurs when a river’s level rises so much that it spills over its banks

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22
Q

What does a shorter lag time result in

A

Shorter lag time = peak discharge is higher = flooding is more LIKELY TO OCCUR

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23
Q

Explain how heavy rainfall affects flood risk

A

Heavy rainfall means that water arrives too quickly to infiltrate, so there’s a lot of surface runoff, which increases the discharge (into river channels)

24
Q

Explain how geology affects flood risk

A

Clay soils and some rocks e.g. granite and shale, are impermeable (they don’t allow infiltration), so surface runoff is increased (into river channels)

25
Q

Explain how prolonged rainfall affects flood risk

A

Prolonged rainfall can saturate the soil
Any further rainfall can’t infiltrate, increasing surface runoff into river channels

26
Q

Explain how relief affects 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

27
Q

Explain how land use affects flood risk

A

Buildings are often made from impermeable materials (e.g. concrete) and surrounded by rounds made from impermeable surfaces (e.g. tarmac), increasing surface runoff

Man-made drains then quickly transport runoff to rivers, increasing discharge

Trees intercept rainwater on their leaves, which then evaporates.
Trees also take up and store water from the ground. This means that curing down trees increases the volume of water that enters the river channel

28
Q

State some types of different management strategies (FOR FLOODING)

A

Hard engineering
Soft engineering

29
Q

What is hard engineering

A

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

30
Q

Examples of hard engineering

A

dams and reservoirs,
straightening, embankments, flood relief
channels

31
Q

Explain the method of dams and reservoirs

A

Dams are barriers built across the rivers, usually in the upper course

A reservoir (artificial lake) is formed behind the dam

32
Q

Adv. of dams and reservoirs

A

Reservoirs store water (e.g. after heavy rain), control water flow and prevent flood downstream

They can also be used to generate hydroelectric power (HEP)

33
Q

Disadv of dams and reservoirs

A

Dams are very expensive to build. Creating a reservoir can flood existing settlements

Material is deposited in the reservoir, not along the river’s course, so farmland downstream can become less fertile.

34
Q

What is channel straightening

A

Meanders are removed by building straighter, artificial channels

35
Q

Benefits of channel straightening

A

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

36
Q

Disadvantages of channel straightening

A

Flooding may happen downstream instead.

Faster-moving water may cause more erosion downstream

37
Q

What are embankments

A

Embankments are raised walls built along the river banks

38
Q

Adv. of embankments

A

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

39
Q

Disadvantages to embankments

A

They are quite expensive

there is a risk of sever flooding, if the water rises above the level of the embankments or if they break

40
Q

What are flood relief channels

A

Channels that are built to divert water around built-up areas or to divert excess water if the river level gets too high

41
Q

Advantages of flood relief channels

A

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

42
Q

Disadvantages of flood relief channels

A

There will be increased discharge where the relief channel rejoins the river (or joins another river), which could cause flooding in that area

43
Q

What is soft engineering

A

Soft engineering is schemes set up using knowledge of a river and its processes to reduce the effects of flooding

44
Q

What is flood warnings and preparation

A

The Environmental Agency issues flood warnings through various media (e.g. TV, radio, internet)

Buildings are modified to minimise flood damage.

Residents can prepare sandbags and flood boards prior to floods

45
Q

Advantages/benefits to flood warnings and preparations

A

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

This reduces the impact of flooding

46
Q

Disadv. to flood warnings and preparation

A

Warnings don’t prevent floods
People may not have access to the warnings

Modifying buildings is expensive

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

47
Q

What is flood plain zoning

A

Flood plain zoning are restrictions that prevents building on parts of a flood plain that are likely to be affected by a flood

48
Q

Adv of flood plain zoning

A

Flood risk is reduced since fewer impermeable surfaces are created (e.g. roads)

The impact of flooding is also reduced as there are no buildings to damage

49
Q

Disadvantages of flood plain zoning

A

The expansion of an urban area is limited if there aren’t any other suitable building sites

It can’t help in areas with existing buildings

50
Q

What are planting trees

A

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

51
Q

Adv. of planting trees

A

Discharge and flood risk decrease
This is because planting trees in the river valley increases the interception of rainwater (and lag time increases)

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

52
Q

Disadv. of planting trees

A

Less land is available for farming

53
Q

What is river restoration

A

River restoration is making the river more natural. For example by removing man-made levees, so that the flood plain can flood more naturally

54
Q

Adv. of river restoration

A

Discharge is reduced so there’s is less is less risk of flooding downstream

Little maintenance is needed and there are better habitats for wildlife

55
Q

Disadv. of river restoration

A

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

GCSE Geography (31 decks)

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