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Geography > Rivers > Flashcards

Rivers Flashcards

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1
Q

What is mechanical weathering (freeze thaw)?

A

When water freezes it expands by 10% causing the break down of the rock.

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2
Q

What is chemical weathering (acid rain)?

A

Rainwater is slightly acidic. When rain falls on Rock, a weak chemical reaction takes place causing the rock to weaken and breakdown

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3
Q

What is biological weathering?

A

Actions of plants and animals causing the rocks to breakdown. e.g. Tree roots can widen cracks in the rocks causing them to breakdown.

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4
Q

What is abrasion?

A

When fragments of rock are picked up by the waves and thrown against river bank causing pieces of rock to fall off

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5
Q

Whats hydraulic action?

A

When the water crashes against the river bed and Bank and the weight of water causes the breakdown of rock. Air is also compressed into cracks causing pressure to build up and break down rock.

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6
Q

What is attrition?

A

Rocks and pebbles carried by the water are reduced in size as they collide against each other and the river bed/bank

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7
Q

What is solution?

A

Chemical action on rocks by river water. It is most effective on limestone rocks.

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8
Q

What are the types of erosion?

A

Abrasion, hydraulic action, attrition and solution

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9
Q

Whats soil Creep?

A

Where individual particles of soil move slowly down a slope

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10
Q

Whats sliding?

A

Where material moves rapidly downslope in one go, e.g. in a landslide. In a Slump, material often rotates as it moves

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11
Q

What is flows?

A

Where masses of soil or rock, usually mixed with water, flow like liquid downhill

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12
Q

What are the types of mass movement?

A

Soil creep, sliding and flows

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13
Q

Whats deposition?

A

Deposition occurs when there is not enough energy to carry eroded material any further. As a river discharge and velocity reduce, the heaviest material us deposited e.g. After flooding

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14
Q

Whats traction?

A

Large boulders/stones roll along the bed

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15
Q

Whats saltation?

A

Smaller stones are bounced along the river bed

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16
Q

Whats suspension?

A

Silt and clay sized particles are carried along within the water flow

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17
Q

Whats solution?

A

Some minerals dissolve in the water and are carried along in the water flow

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18
Q

What is the gradient like along the river?

A

Upper course: steep
Middle course: less steep
Lower course: shallow

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19
Q

Whats the discharge like along the river?

A

Upper course: low
Middle course: high
Lower course: very high

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20
Q

Whats the depth like along the river?

A

Upper course: shallow
Middle course: deeper
Lower course: deep

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21
Q

Whats the channel shape along the river?

A

Upper course: narrow, steep sides
Middle course: flat, steep sides
Lower course: flat floor gently sloping sides

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22
Q

Whats the velocity like along the river?

A

Upper course: quite fast
Middle course: fast
Lower course: very fast

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23
Q

Whats the valley profile like along the river?

A

Upper course: steep sides
Middle course: flat with steep sides
Lower course: flat with gently sloping sides

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24
Q

What are the features like along the river?

A

Upper course: waterfalls, interlocking spurs
Middle course: meanders, flood plains
Lower course: meanders, flood plains, levees, Ox bow lakes

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25
Q

What is the sediment size and shape like along the river?

A

Upper course: angular boulders
Middle course: rounded rocks
Lower course: smooth rounded pebbles/sand

26
Q

What is the upper course of the river dee like?

A

•Source is 460m above sea level on the slopes of Ddualt in snowdonia national park
•geology is hard igneous rock meaning more resistant to erosion so river source is narrow erodes vertically forming v shaped valley
•sediment is angular stones

27
Q

What is the middle course of the the river dee like?

A

•Valley becomes flatter and wider creating areas of floodplain + its gradient decreases
•erodes sideways and downwards
•some deposition on inside bends of meanders which form point bars
•sediment is rounder and smoother
•as tributaries join discharge increases

28
Q

What is the lower course of the river dee like?

A

•average annual rainfall 750mm
•flows thru softer rock like 🏖🪨 towards Chester
•wide deep valley with flat bottom
•high sediment load
•flows for 110km until reaches the Irish Sea between Wales and river peninsula

29
Q

How does increased frequency of of storm impact the weather and climate?

A

More rainfall means more water flowing in rivers which then overflows increasing flood risk

30
Q

How does increasing periods of hot, dry weather (drought) influence climate?

A

Bakes upper soil so when there is rainfall water isn’t absorbed to soil. Increasing surface run off into rivers increasing river discharge

31
Q

Whats the impact of cold conditions?

A

Soil becomes impermeable so snow melt cannot infiltrate and flows rapidly into river increasing flood risk

32
Q

What is the impact of erosion rate?

A

Increases with greater discharge. In wet climates more material is eroded, widening and deepening river channels as we as sediment load

33
Q

What is the impact of weathering?

A

Will be greater in some climates. Freeze thaw weathering increases in areas where temperatures around freezing

34
Q

What is the impact of river discharge?

A

•Wetter climates mean greater discharge
•Hotter temperatures mean greater evaporation so less discharge
Greater discharge = greater velocity

35
Q

What is the impact of transport?

A

Greater where energy of water is greater. Rivers in wet climate will transport more material than those dry

36
Q

What are the physical causes of flooding?

A

Rain, snow melt, geology, relief

37
Q

How does rain cause flooding?

A

Soil and rocks become saturated. It is therefore unable to infiltrate leading to increased surface runoff

38
Q

How does snow melt cause flooding?

A

When there’s more snow in winter and it melts in the spring the melted snow flows into rivers increasing the likelihood of rivers overflowing and flooding

39
Q

How does geology cause flooding?

A

•Permeable rocks allow water to percolate reducing surface run-off
•impermeable rock do not allow water to pass thru increasing surface runoff and therefore flooding

40
Q

What are embankments/levees?

A

High banks built on or near River banks

41
Q

What is channelisation?

A

Deepening and/or straightening the channel

42
Q

What ate flood relief channels?

A

Extra channels built next to rivers/leading from them

43
Q

What are dams and reservoirs?

A

Barriers constructed to hold back water in artificial lakes

44
Q

What are washlands?

A

Areas on the flood plains that are allowed to flood

45
Q

What is river restoration?

A

Restoring the rivers original course

46
Q

What is flood-plain zoning?

A

Land is allocated different uses depending on the flood risk

47
Q

What are the advantages and disadvantages of embankments/levees?

A

+stops water spreading into other areas
-can burst under pressure

48
Q

What are the advantages and disadvantages of channelisation?

A

+allows water to flow more quickly from areas of flood risk
-more water is taken downstream increasing flood risk elsewhere

49
Q

What are the advantages and disadvantages of flood relief channels?

A

+Can hold high flows so flooding doesn’t occur
-can be expensive

50
Q

What are the advantages and disadvantages of dams and resoviors?

A

+can be used to produce HEP
-social costs as people displaced

51
Q

What are the advantages and disadvantages of washlands?

A

+provides a safe place for floodwater to go
-allowing land to flood may limit its use

52
Q

What are the advantages and disadvantages of river restoration?

A

+natural rivers are more attractive and create natural habitats for wildlife
-some flood banks are still needed

53
Q

What are the advantages and disadvantages of flood-plain zoning?

A

+reduces number of homes at risk of flooding
-restricts settlement growth

54
Q

What are the hard engineering (man made defences) methods of flood management?

A

Embankments/levees
Channelisation
Flood relief channels
Dam and resovoirs

55
Q

What are the methods of soft engineering (natural materials) for managing floods?

A

Washlands
River restoration
Flood-plain zoning

56
Q

What percentage of the river dee catchment is rural?

A

95%

57
Q

How many people rely on the river for a water source?

A

3 million people in Wales and North West England

58
Q

What does the river dee support?

A

Large areas of important habitats, including rare plant and wildlife species such as the otter and water vole

59
Q

What is the river dee famous for?

A

Commercial and recreational fishing

60
Q

8km of channelisation of the river dee improved navigation between?

A

1972 and 1976

Geography (12 decks)

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