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Rivers Flashcards

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1
Q

Name the parts of a river.

A

Source
Drainage basin
Confluence
Tributary
Watershed
Estuary

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2
Q

Define the source, confluence and Tributary of a river.

A

Source: start of a river, usualy high ground
Confluence: Where a tributary joins a larger river
Tributary: a small stream that joins a larger river

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3
Q

Define the drainage basin, watershed and Estuary of a river.

A

Drainage basin: area of land drained by a river+ tributaries
Watershed: the edge of a river basin
Estuary: end of a river usualy where it meets the sea

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4
Q

What does the long profile of a river mean?

A

A line representing a river from its source to its mouth showing the altitude of the river changes.

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5
Q

What does a cross section of a river mean?

A

Shows a cross section of the rivers channel and valley at a certain point along the rivers course.

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6
Q

Describe features of the Upper course of a river.

A
  • Narrow and shallow in a highland area
  • the valley is very steep and mountainous
  • sediment size is big and more angular
  • mostly vertical errosion
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7
Q

Describe features of the Middle course of a river .

A
  • river is wider and deeper
  • sediment size is smaller and less angular than the upper course
  • erroding and transporting
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8
Q

Describe features of the Lower course of a river .

A
  • river is very wide and deep
  • relief is lowland
  • sediment size is smallest, aluvium.
  • angularity of sediment = rounded
  • deposition happens
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9
Q

Why does the size of a rivers sediment decrease in size going down a river?

A

Because sediment is erroded, broken down through attrition on its journey.

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10
Q

Explain the two types of erosion that occur in a river.

A

Vertical = downward errosion that makes a river channel deeper. It happens more in the upper course causing a V shape.
Lateral = sideways erosion makes a river wider and occurs more in the middle+lower course.

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11
Q

How does the cross profile of a river valley change going down stream?

A

This changes downstream from being steep and V shaped to slowly becoming flatter and wider land.

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12
Q

How does the rivers velocity change further downsteam?

A

As material is transported downstream the rivers velosity will slow down at the end of a river. As a result deposition will occur in the estuary.

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13
Q

How does a river change as you go downstream?

A

Upper course Lower course
Narrow & shallow → deep & wide
Highland → Lowland
Sediment:
Big rocks → small sediment, aluvium
Angular → rounded
Valley:
V=Mountaious & V shaped → Fland and wide land

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14
Q

Name 3 overall reasons for deposition occurring at points along the river.

A
  • River mouth meets the sea, going in opposite directions
  • on the inside of a bend water is flowing slowly
  • River floods over the river channel and obsticles slow it down
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15
Q

Explain why deposition occurs at a river Estuary.

A

At a river estuary the river meets the sea and slows down because the sea is coming in the opposite direction so it loses energy so it deposits material

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16
Q

Explain why deposition occurs at a river Bend.

A

Deposition occurs on the inside of a river bend because the water flows more slowly so it loses energy so it deposits

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17
Q

Explain why deposition occurs when a river floods.

A

When a river floods the water slows down because there are **many obsticles **on the river banks (friction) so the river loses energy so it deposits material on the floodplain.

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18
Q

Name the coastal landforms that are found in a rivers upper, and middle course.

A

Upper = Gorges (erosion)
Waterfalls (errosion)
Interlocking Spurs (erosion)
Middle = Meanders
Oxbow Lakes (erosion & deposition)

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19
Q

Name the coastal land forms found in a rivers lower course.

A

Estuary (deposition)
Floodplains (deposition)
Levee (deposition)

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20
Q

Describe how sediment is transported by a river.

A

Sediment is moved downstream by a river. Small sediment is carried in suspension and larger pebbles are moved along the river bed in ‘jumps’ which is saltation. Large material is rolled along the river bed by traction.

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21
Q

What are interlocking Spurs?

A

In the upper course there is more vertical erosion, the river cuts down into the valley creating V shapes. If there is hard rock which is harder to errode the river will just bend around it. This creates interlocking spurs.

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22
Q

Explain the formation of a waterfall.

A

Water runs over hardrock layer with soft rock underneath. The soft rock will erode quicker by HA+abraision. So eventually the hard rock is undercut, when unsupported it will colapse into the river. Fallen rocks will either be transported downstream or be used to further errode. This with the friction of water will errode into a plunge pool a dip in the river bed.

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23
Q

Explain how Gorged are formed.

A

Water runs over hard rock with soft rock underneath.
Soft rock eroded quicker by HA+abraision.
Hardrock is undercut and because its unsupported will colapse into river bed.
Fallen rocks are transported or used for futher erosion.
This with water friction will errode a dent in the river bed =** plung pool.**
Ersoion process will repeat and slowly the waterfall retreats forming a steep sided gorge.

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24
Q

Define Meanders.

A

A pronounced bend in a river found mainly in lowland areas forms because of lateral errosion and deposition.

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25
Q

How do meanders form?

A

Water will try to find the quickest course Most water is pushed to the outside of a bend, increased speed means more energy so the outsid will be erroded.Water on the inside of the bend is slower so it has less energy so it deposits material creating a gentle slope. Due to errosion on the outside and depositio on the inside the meander will move and change overtime.

26
Q

Define Oxbow lakes.

A

An arc shaped lake wich has been cut off from a meander in a river. Found in the middle course.

27
Q

How do Oxbow lakes form?

A

Due to erosion of the outside of a bend and deposition on the inside the meander shape will change. Erosion causes the outsides to get closer leaving a small peice inbetween two meanders -** ‘meander neck’**. When there is very high discharge the river will cut across taking a shorter route. Deposition will then cut of the original meander leaving an oxbow lake.

28
Q

Define Floodplains.

A

An area either side of a river that is made up of layers of sediment that is deposited overtime by a series of floods.

29
Q

Explain the formation of Floodplains.

A

In the middle course meanders move overtime carving out a wide nd flat valley bottom. When the river floods it deposits aluvium on the floodplain, either side of the channel.With biggest material deposited first this builds up layers of sediment on the floodplain every time it floods.

30
Q

Define Levees.

A

A levee is a raised river side, embankment. Found along side a river it builds up over time from sediment deposited in floods.

31
Q

How do levees form?

A

When a river floods friction slows the water down so it loses energy so it deposits sediment. Heaviest marterial is deposited first at closest point to a river because water doesnt have enough energy to carry it. Smaller material is deposited further away. With more flooding sediment layers build up and the levee gets higher.

32
Q

Define Estuaries.

A

Is the tidal part of a river where fresh water from the river meets the salt sea water. Where the river and sea meet rivers velosity falls and sediment is deposited this can form mudflats that may develop into salt marshes.

33
Q

Name all the landforms that can be found along a rivers course.

A

Interlocking spurs
Waterfall
Meanders
Oxbow lake
Levee
Estuary

34
Q

What are the physical and human reasons for flooding?

A

Urbanisation
Deforestation
Heavy rainfall
Impermeable rock
Drought

35
Q

Explain why Heavy rainfall is a cause of flooding.

A

Lots of water arrives at the same time so lots reaches the river increasing discharge creating a flood. If it rains a long time soil becomes saturated, cant absorbe more, so surface run off increases so water reaches river quicker = flooding.

36
Q

Explain why Impermeable rock is a cause of flooding.

A

Impermeable means water cannot infiltrate the rock so runoff is increased when it rains causing discharge to increase quickly so the river floods.

37
Q

Explain why Drought is a cause of flooding.

A

Lack of rainfall. if there has been a drought the soil can be baked dry when this happens water cant infiltrate so runs over the surface, quickly getting to river so it floods.

38
Q

Explain why Deforestation is a cause of flooding.

A

Trees intercept rain with their leave and then it evaporated water is also taken up by their roots. If removed then the quantity of water getting to the river increases, increasing the risk of flooding.

39
Q

Explain why Urbanisation is a cause of flooding.

A

If land is urban many of the surfaces are impermiable so water cant infiltrate and runs over surface quickly to rivers, water is also directed to drains. This increases the dishcharge of the river causing flooding.

40
Q

What are hydrographs?

A

A graph that tells us how quickly rivers discharge responds ro a rainfall event.

41
Q

Explain what lag time, peak discharge and peak rainfall.

A

Lag time is from the peak rainfall to peack discharge.
Peak discharge is the highest amount of water in the river.
Peak rainfall is the highest amount of rainfall.

42
Q

Name the hard engineering processes for River Management.

A

Dams
Straightening Rivers
Embankments
Flood relief channel

43
Q

Explain how Dams prevent flooding.

A

Buildig a concrete or earthstructure to stop the flow of the river and create an artificial lake, resevoir. People can control water flowing in the river and so can prevent flooding.

44
Q

Explain how Flood relief channels prevent flooding.

A

New channel built of a main river that can take excess water at times of high discharge preventing the main river from flooding

45
Q

Explain how Embankments prevent flooding.

A

Artificialy raised river banks made of earth or concrete raised sides means the river channel can hold more water so less chance of a flood.

46
Q

Explain how Straightening rivers reduce / prevent flooding.

A

Cutting off old meanders to artificialy create a new straight water channel stops flooding as water can flow away very quickly.

47
Q

What are costs and benefits for Dams?

A

ADVANTAGES
- new lake ecosystem
- recreation and tourism
- hydroelectric power
DISADVANTGES
- floods homes and habitats for the resevoir
- very expensive
- slit buids up reducing water capacity

48
Q

What are costs and benefits for Straighenting Rivers?

A

ADVANTAGES
- reduces insurance cost in the area
- very effective
DISADVANTGES
- increased flood risk down stream
- high maintenance
- expensive
- unnatural

49
Q

What are costs and benefits for Flood relief Channels?

A

ADVANTAGES
- effective in reducing flooding in towns
- creates new aquatic habitats
- effective
-recreation
DISADVANTGES
- expensive if construcing over high value land
- loss of habitat
- regular maintenance needed

50
Q

What are costs and benefits for Embankments?

A

ADVANTAGES
- reduced flood risk
- river bank habitats created
- walkway
DISADVANTGES
- regular maintenance needed
- if embankment fails can lead to more serious floods

51
Q

What is soft engineering for river management?

A

Attempts to work with the natural process active on a river. It doesnt always stop flooding but reduces the risk.

52
Q

What is hard engineering for river management?

A

involves major construction work to prevent the river flooding

53
Q

Explain how Afforestation reduces flooding.

A

More trees planted intercepts precipitation reducing the maount of water that may flow into a river. Trees also absorbe water.

54
Q

Explain how Flood warnings reduce the effects flooding.

A

Rivers are consistantly monitored in order to predict flooding so wrnings can be issued and epople evacuated.

55
Q

Explain how Floodplain Zoning reduce the effects flooding.

A

Council planning restricts land use in high flood risk areas so that high value land is not in flood prone areas. So floods have less impactful effect.

56
Q

Explain how River restoration reduces flooding.

A

Restoring straight river channels to meandering patterns slows water flow. Some areas will floods but there is reduced risk downstream.

57
Q

What are costs and benefits for River restoration?

A

ADVANTAGES
- natural environment
- reduced flood risk downstream
- biodiversity created from wetland areas on floodplain
DISADVANTGES
- expencive to construct and maintain new channel
- when land floods inconvenience to locals
- change in land use

58
Q

What are costs and benefits for Flood warning?

A

ADVANTAGES
- prepare people to act acordingly
- sustainable
- safety without high cost
DISADVANTGES
- needs monitoring equiptment
- people may not respond apropriately

59
Q

What are costs and benefits for Floodplain zoning?

A

ADVANTAGES
- low cost
- reduces additional immpermiable surfaces
- protect habitats by river
DISADVANTGES
- restricts economic development
- hard to impliment in urban areas
- habitats destroyed building elsewhere

60
Q

What are costs and benefits for Afforestation?

A

ADVANTAGES
- natural method
- creates habitats
- not expencive
DISADVANTGES
- can reduce habitat diversity
- lots of trees reduce possible farmland
- trees take a long time to grow

61
Q

Name all soft engineering techniques for river Management.

A

Afforestation
River restoration
Flood warning
Floodpain Zoning

Geography (10 decks)

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