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geography > rivers > Flashcards

rivers Flashcards

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1
Q

upper course gradient, valley and channel shape

A

steep gradient, v-shaped valley, narrow and shallow channel

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2
Q

middle course gradient, valley and channel shape

A

medium gradient, gently sloping valley side, deeper channel

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3
Q

lower course gradient, valley and channel shape

A

gentle gradient, almost flat valley, wide and deep channel

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4
Q

vertical erosions

A

deepens the river valley and channel making v-shaped

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5
Q

lateral erosion

A

widen the river valley and channel

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6
Q

4 processes of erosion

A

-hydraulic action
-abrasion
-attrition
-solution

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7
Q

hydraulic action

A

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

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8
Q

abrasion

A

eroded rocks picked up by the river scrape and rub along the channel, wearing it away

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9
Q

attrition

A

eroded rocks picked up by the river crash into each other and break into smaller fragments

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10
Q

solution

A

river water dissolved some types of rock

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11
Q

4 processes of transportation

A

-traction
-suspension
-saltation
-solution

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12
Q

traction

A

large particles are pushed along the river bed by the force of the water

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13
Q

suspension

A

small particles like silt and clay are carried along by the water

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14
Q

saltation

A

pebble-sized particles are bounced along the river bed by the force of the water

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15
Q

solution

A

soluble materials dissolve in the water and are carried along

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16
Q

what is deposition

A

when a river drops the material it’s transporting

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17
Q

why does deposition occur

A

when the river loses velocity and energy

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18
Q

how does particle size affect deposition

A

smaller particles are transported further and are deposited closer to the river’s mouth

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19
Q

formation of waterfalls

A

-softer rock is eroded more than the hard rock, creating a step
-a steep drop is eventually created, a waterfall

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20
Q

formation of gorges

A

-hard rock is eventually undercut by erosion, it becomes unsupported and collapses
-the collapsed rock erodes the softer rock by abrasion creating a deep plunge pool
-more undercutting causes more to collapse. The waterfall retreats leaving behind a steep sided gorge

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21
Q

interlocking spurs

A

-in the upper course of a river most of the erosion is vertical, creating v-shaped valleys.
-the river doesn’t have enough power to erode laterally so they have to wind around the hillsides

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22
Q

landforms formed by erosion

A

waterfalls, gorges and interlocking spurs

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23
Q

landforms formed by erosion and deposition

A

meanders and oxbow lakes

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24
Q

how are meanders formed

A

-the current is faster on the outside of the bend because the river channel is deeper
-more erosion takes place on the outside of the bend forming river cliffs
-the current is slower on the inside of the bend because the river channel is shallower, so eroded material is deposited on the inside of the bend, forming slip-off slopes

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25
Q

oxbow lake formation

A

-meanders get larger over time, erosion causes the outside bends to get closer
-the river breaks through the small bit of land in between and the river follows the shortest course
-deposition eventually cuts off the meander forming an oxbow lake

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26
Q

landforms formed by deposition

A

-levees, flood plains and estuaries

27
Q

floodplains

A

-the wide valley floor on either side of a river which occasionally floods
-when rivers flood, the water slows down, loses energy and deposits the material that its transporting

28
Q

levees

A

-natural embankments along the edges of a river channel
-during a flood, eroded material is deposited closest to the river channel because it get dropped first when the river slows down and loses energy
-the deposited material builds up creating levees along the edges of the channel

29
Q

estuaries

A

-found a the mouth of the river
-when the water floods over the banks of the river it carries silt and sand onto the valley floor
-as the tide reaches its highest point, the water moves slowly and has little energy so it deposits sediment
-over time, more mud builds up creating large mudflats
-at low tide the muddy banks are exposed

30
Q

physical factors affecting flood risk, 4

A

-heavy rainfall
-geology
-prolonged rainfall
-relief

31
Q

human factors affecting flood risk

A

-land use

32
Q

how does land use affect flood risk

A

-buildings made from impermeable materials increase surface runoff, man-made drains transport runoff to rivers, increasing discharge
-trees intercept rainwater on their leaves which then evaporates, cutting down trees increases the volume of water that enters the channel

33
Q

peak discharge

A

highest discharge in the period of time

34
Q

lag time

A

delay between peak rainfall and peak discharge

35
Q

rising limb

A

increase in river discharge as rainwater flows into the river

36
Q

falling limb

A

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

37
Q

why does lag time occur

A

most rainwater doesn’t land directly in the river channel, it flows quickly overland or soaks into the ground then flows to the channel

38
Q

what is hard engineering

A

man-made structures built to control the flow of rivers and reducing flooding

39
Q

hard engineering strategies

A

-dams and reservoirs
-channel straightening
-embankments
-flood relief channels

40
Q

what are flood relief channels

A

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

41
Q

benefits of dams and reservoirs

A

-used to generate hydroelectric power
-prevent floods downstream

42
Q

benefits of channel straightening

A

water leaves the area more quickly rather than building up

43
Q

benefits of embankments

A

the river can hold more water, less flooding

44
Q

benefits of flood relief channels

A

gates on the channels mean that the release of water can be controlled

45
Q

dams and reservoirs disadvantages

A

-expensive
-floods existing settlements

46
Q

channel straightening disadvantages

A

-flooding downstream instead
-faster-moving water may cause erosion downstream

47
Q

embankments disadvantages

A

-expensive
-severe flooding if the water level rises or if they break

48
Q

flood relief channel disadvantages

A

-increased discharge where the relief channel rejoins the river could cause flooding

49
Q

what is soft engineering

A

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

50
Q

soft engineering strategies

A

-flood warnings and preparation
-flood plain zoning
-planting trees
-river restoration

51
Q

benefits of flood warnings and preparation

A

warnings give people time to move possessions and evacuate

52
Q

benefits of flood plain zoning

A

fewer impermeable surfaces created, no buildings to damage

53
Q

benefits of planting trees

A

discharge and flood risk decreased
reduces soil erosion creating habitats

54
Q

benefits of river restoration

A

less risk of flooding downstream, little maintenance needed

55
Q

flood warnings and preparation disadvantages

A

warnings don’t prevent floods, expensive

56
Q

flood plain zoning disadvantages

A

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

57
Q

planting trees disadvantages

A

less land is available for farming

58
Q

river restoration disadvantages

A

local flood risk can increase

59
Q

why was a flood management scheme needed on the river tees

A

-the steep v-shaped valleys in the upper course of the river are made of impermeable rock, increasing run-off and causing river levels to rise
-almost 23,500 people at risk of flooding

60
Q

river tees management strategies (6)

A

-flood gates
-gabions
-flood warnings
-flood plain zoning
-the Tees barrage
-Cow Green reservoir

61
Q

river tees flood management - social issues

A

-hard engineering is unattractive
-flooding continues to disrupt

62
Q

river tees flood management - economic issues

A

-tees barrage cost £54 million
-flood defences are expensive to maintain

63
Q

river tees flood management - environmental issues

A

-28 environmentally designated sights in the area at risk from flooding that require protection

geography (11 decks)

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