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Geography- Rivers > River Land Forms- The River Valley > Flashcards

River Land Forms- The River Valley Flashcards

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1
Q

what is the course

A

the path of a river as it flows downhill

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2
Q

features found in the upper course of a river

A

steep gradient
v shape valley
shallow chanell
fast flowing water
erosional processes
waterfalls
gorges

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3
Q

features found in the middle course of a river

A

medium gradient
gently sloing valley
meanders
ox-bow lakes
levees
deeper channel

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4
Q

features found in the lowe course of a river

A

gentle gradient
very wide channel
deep channel
estuaries
mouth of the river

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5
Q
A
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6
Q

vertical erosion

A

erosion that deepens the river valley and channel causing V-shaped valleys.
found in the upper course of a river.
high turbulence of the water causes the rough angular particles to be scraped along river bed,

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7
Q

lateral erosion

A

widens the river valley and channel during formation of meanders.
usually in middle and lower courses of the river

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8
Q

hydraulic action

A

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

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9
Q

abrasion

A

eroded rocks picked up the river scrape and rub against the channel wearing it away.
most erosion happens by abrasion

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10
Q

attrition

A

eroded rocks picked up by river crash into each other and break into smaller pieces
causes particle size to decrease from source to mouth

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11
Q

solution

A

river water dissolves some type of rock (chalk and limestone)

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12
Q

traction

A

large particles are pushed along the river bed by water force

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13
Q

saltation

A

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

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14
Q

suspension

A

small particles (silt, clay) a carried by the water

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15
Q

solution

A

soluble materials (limestone) dissolve and are carried by the water

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16
Q

deposition

A

.a river drops eroded material
.occurs when river loses velocity and energy
dominant in lower course

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17
Q

why do rivers slow down and deposit material

A

.volume of water falls
. the amount of eroded material increases
. the water is shallower
the river reaches mouth

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18
Q

how are waterfalls formed

A

1.)when a river flows over an area of hard rock
2.) the softer rock is eroded(hydraulic action and abrasion) forming a step in river
3.) over time, a steep drop is created (waterfall)
4.) hard rock undercut by erosional processes- collapses
5.)

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19
Q

how is a plunge pool created

A

hard collapsed rocks undercut the soft rock at the bottom of the waterfall, via vertical abrasion

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20
Q

how is a gorge formed

A

over time more undercutting leads to waterfall being pushed back, causing behind a steep gorge

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21
Q

what a meanders

A

large bends in a river
found in the middle and lower courses in a river formed by erosion and deposition

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22
Q

how are meanders formed

A

1.)current is faster on the outside of the bend (river channel is deeper)
2.) more erosion takes place on the outside of a bend- forming river cliffs
3.) current is slower on the inside bend of a river, because river channel is slower
4.) more material is deposited on the inside of the bend, forming slip of slopes

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23
Q

how are ox-bow lakes formed

A

1.)erosion over times causes the inside bends to get closer until only a small bit of land between rock (neck)
2.) river breaks through this land and flows through the shortest course
3.) deposition over time cuts of meander, forming an ox-bow lake

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24
Q

flood plain

A

wide valley floor on each side of the river that flood
found in middle and lower courses of river

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25
Q

how do flood plains build up

A

when rivers flood, water slows down losing energy and deposits material on each side of the river- building up the flood plain
deposition that happens on the slip of slope of meanders build up the flood plain

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26
Q

levees

A

natural embankments along the edges of a river channel

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27
Q

how to levees build up

A

during a flood, eroded material is deposited over whole flood plain
over time deposited material builds up, creating levees along the edges of the channel

28
Q

esturies

A

tidal areas where the river meets the sea
found in the lower course of a river
estuary water is tidal- water level rises and falls each day

29
Q

river discharge

A

the volume of water flowing in a river per second

30
Q

what is river discharge measured in

A

cumecs (cubic metres per second

31
Q

hydrographs

A

show how the discharge at a certain point in a river changes in relation to rainfall

32
Q

1.) peak discharge

A

the highest discharge in the period of time that is being recorded

33
Q

2.) lag time

A

the delay between peak rainfall and peak discharge

34
Q

3.)rising limb-

A

the increase in river discharge as the river returns to normal level

35
Q

4.)falling limb-

A

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

36
Q

how is lag time affected by physical and human factors

A

lag time occurs because most rainfall doesnt land in a river channel
either flows as surface runoff or soaks into the ground (infriltration)

37
Q

Heavy rainfall

A

Heavy rainfall means that water arrives too quickly to infriltrate, so there is more surface runoff- increases discharge

38
Q

geology

A

clay soils and some rocks (granite) are impermeable(don’t allow infiltration) so runoff is increased

39
Q

prolonged rainfall

A

prolonged rainfall can saturate the soil. Any further rainfall cannot infiltrate, increasing runoff in river channels

40
Q

relief (changes in land heights)

A

if a river is in a steep sided valley, water will reach river channel quicker increases discharge

41
Q
A
42
Q

Hard engineering

A

.Man made structures built to control water the flow of rivers and reduce flooding
This can reduce the risk of flooding

43
Q

What Dams and reservoirs

A

Barriers built across rivers
Found in the upper course
Reservoirs are artificial lakes formed behind a dam

44
Q

Benefits of dams and resovoirs

A

Reservoirs store water after heavy rain, control water flow and prevent flood’s downstream
Generate hydroelectric power

45
Q

Disadvantages of dams and reservoirs

A

Dams are very expensive to build.
Reservoirs can flood existing settlements
Material is deposited in the reservoir,. So farmland downstream can become less fertile.

46
Q

What is channel straightening

A

Meanders are removed by building artificial straighter channels

47
Q

Benefits of channel straightening

A

Water leaves the area more quickly so flood risk is lower

48
Q

Disadvantages of channel straightening

A

Flooding may happen downstream instead.
Faster moving water causes erosion downstream

49
Q

What are embankments

A

Raised walls are built along river banks

50
Q

Advantage of embankments

A

River can hold more water so floods are less frequent

51
Q

Disadvantages of embankments

A

Very expensive
Risk of severe flooding if water rises above level of embankment

52
Q

Flood relief channel

A

Channels are built to divert water around Built up areas to divert excess water if level gets to high

53
Q

Benefits of flood river channel

A

Gates on the channel mean the release of water can be contolled- reducing flood risk

54
Q

Disadvantages of flood relief channels

A

Increased discharge where the relief channel rejoins the river- causing flooding in that area

55
Q

Soft engineering

A

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

56
Q

What is Flood warning and preparation

A

Environment agency issues flood warning through forms of media eg radio, tv.
Buildings are modified to minimise flood damage- residents also prepare sandbags and boards prior to flooding

57
Q

Benefits of flood warnings and preparation

A

Residents have more time to prepare and move possessions upstairs use sandbags etc
This reduces impact of flooding

58
Q

Disadvantages of flood warnings and preparation

A

Warnings don’t prevent actual floods
People may not have access to the warnings
Expensive to modifying buildings

59
Q

Flood plain zoning

A

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

60
Q

Benefits of flood plain zoning

A

Flood risk is reduced (fewer impermeable surfaces are created)
Impact or flooding is reduced
(No buildings to damage)

61
Q

Disadvantages of flood plain zoning

A

Expansion of urban is limited
Can’t help in existing buildings

62
Q

Planting trees

A

Planting trees in the river valley increases interception of rainwater

63
Q

Benefits of planting treesc

A

Discharge and flood risk decrease
Vegetation reduces soil erosion- provides habitats for wildlife

64
Q

Disadvantages of planting trees

A

Less land available for farming

65
Q

River restoration

A

Making river more natural, by removing man made levees, so plain can flood naturally

66
Q

Benefits of river restoration

A

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

67
Q

Disadvantages of river restoration

A

Local flood risk can increase. Especially if nothing is done to prevent flooding

Geography- Rivers (6 decks)

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