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Geography > Rivers > Flashcards

Rivers Flashcards

1
Q

define drainage basin

A

an area of land drained by a river and its tributaries

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2
Q

define watershed

A

the border between drainage basins E.g hills

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3
Q

source of a river

A

the beginning of the river

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4
Q

mouth of a river

A

the end of the river
where it meets the sea

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5
Q

what is a confluence

A

where 2 rivers meet

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6
Q

what is a tributary

A

when a smaller river joins a larger river

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7
Q

river channel

A

the area the water takes up

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8
Q

where does vertical erosion occur and what does it form

A

occurs in the upper course
forms V-shaped valleys

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9
Q

where does lateral erosion occur and what does it form

A

occurs in the middle & lower course
forms wide valleys

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10
Q

when does a river deposit material

A
  • going around a bend- material deposited on inside bend
  • during flooding
  • at the mouth when freshwater meets seawater- mudflats are formed
    -at the end of the river
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11
Q

what is a long profile
describe the long profile of a river

A

shows changes in the height of the course of a river from its source to its mouth

Upper course - river’s load is large as it hasn’t been broken down by erosion yet. narrow valley sides

Lower course - land is flatter. river’s load is fine sediment, as erosion has broken down the rocks.

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12
Q

what is a cross profile
describe the cross profile of a river

A

show a river’s cross section as it changes with distance downstream

upper course- narrow and steep-sided river channel due to vertical erosion

middle course- wider valley floor due to more lateral erosion than vertical erosion

lower course- almost flat valley floor, only some lateral erosion, river at its widest

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13
Q

fluvial processes

A

processes found in a river

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14
Q

what is erosion

describe the 4 types of erosion

A

erosion is the process which wears away the river bed and bank

  1. hydraulic action- power of water as it smashes against river banks. Air gets trapped in cracks of river bank and bed, causing the rock to break apart

2.abrasion- pebbles grind along the river bank and bed in a sand-papering effect.

3.attrition- rocks carried by the river hit each other. They break apart to become smaller and more rounded

4.solution- the water dissolves certain types of rocks, eg limestone

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15
Q

what is transportation

describe the 4 types of transportation

A

transportation is when the river picks up sediment and carries it downstream.

  1. traction- large, heavy pebbles are rolled along the river bed- most common near source of a river as load is larger.
  2. saltation- pebbles bounce along the river bed, most common near source
  3. suspension- lighter sediment is carried within the water, most common near mouth of the river.
  4. solution- transporting dissolved chemicals
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16
Q

define load

A

the particles of rock carried by a river

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17
Q

describe deposition
when does deposition occur

A

deposition is when the river loses energy and drops material

-shallow water
-at the river’s mouth
-when volume of the water decreases
-areas of low velocity

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18
Q

what landforms result from erosion

A

waterfalls
gorges
interlocking spurs

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19
Q

what landforms result from erosion and deposition

A

meanders
oxbow lakes

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20
Q

what landforms result from deposition

A

levées
floodplains
estuaries

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21
Q

explain the formation of a waterfall and gorge

where are waterfalls found

A

found in upper course

  1. soft rock is eroded quicker than hard rock
  2. hard rock is undercut by erosion (hydraulic action & abrasion), forming an overhang
  3. this forms a plunge pool

4.plunge pool gets bigger and overhang collapses

5.process continues and waterfall retreats upstream

  1. A steep-sided valley is left where the waterfall was. This is a gorge.
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22
Q

explain the formation of interlocking spurs

where are interlocking spurs found

A

found in upper course

In upper course there’s more vertical erosion.

the river bends round areas of hard rock instead of eroding them

This creates interlocking spurs of land which link together

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23
Q

explain the formation of a meander
where are meanders found

A

in middle & lower course

As river goes around bends, water is pushed towards the outside.

This increases speed and increases erosion (hydraulic action and abrasion).

lateral erosion on outside bend undercuts the bank  to form a river cliff.

Water on inner bend is slower, so water slows down and deposits material,
creates a slope of sand and shingle.

The build-up of deposited sediment is a slip-off slope/river beach.

24
Q

explain the formation of an oxbow lake

A

in middle and lower course

meander neck narrows due to lateral erosion

during high river discharge, meander neck breaks.
river takes the shorter, straight route

deposition at the edges cuts off the old meander

the old meander forms an oxbow lake, is horseshoe shaped- separate to river

oxbow lake silts up to form marshland

25
Q

explain the formation of a levée

where are levees found

A

found in lower course

during high river discharge and flooding

Sediment eroded upstream is transported downstream.

during floods, the river loses energy.
large material is deposited first on the sides of the river banks and small material deposited further away.

After many floods, sediment builds up to increase height of the river banks,

the channel can carry a greater discharge

flooding is less likely to occur in the future

26
Q

explain the formation of floodplain

A

in middle and lower course

A floodplain is an area of land covered in water when a river bursts its banks.

Erosion removes interlocking spurs, creating a wide, flat area on both sides of the river.

During a flood, material carried by the river is deposited (as the river loses its speed and energy).
Over time, the height of the floodplain increases as material is deposited on either side of the river.

Floodplains are agricultural land, as the area is fertile because it’s made up of alluvium (deposited silt from a river flood).

27
Q

explain the formation of a estuary

A

lower course

An estuary is where the river meets the sea. (mouth)

The river here is tidal and when the sea retreats, the volume of the water in the estuary is reduced.
When there is less water, the river deposits silt to form mudflats which are habitats for wildlife.

28
Q

3 physical factors of floods

A

precipitation- heavy rainfall saturates soil so water cannot infiltrate into the soil = surface runoff

geology- impermeable rocks don’t let water infiltrate into them =surface runoff

steep slopes- causes rapid water transfer which means a SHORT LAG TIME

29
Q

define lag time

A

the time taken between peak rainfall and peak discharge.

30
Q

3 human factors of floods

A

farming- bare soils transfer water quickly, short lag time

urbanisation- construction using impermeable surfaces such as concrete, water cannot infiltrate

deforestation- trees intercept rainfall and reduce flood risk. if there are less trees, less rain is intercepted= higher flood risk

31
Q

define peak discharge

A

the maximum amount of water held in the channel

32
Q

define peak rainfall

A

the maximum amount of rainfall (mm)

33
Q

define rising limb

A

the increase in discharge on a hydrograph

34
Q

define falling limb

A

the return of discharge to normal/base flow on a hydrograph.

35
Q

define base flow

A

the normal discharge of a river

36
Q

what factors decrease lag time

A

large drainage basin
little vegetation
steep valley sides
impermeable soil type

37
Q

what are hard engineering strategies

list the 4 hard engineering strategies

A

building artificial structures which try to control rivers.

-dams & reservoirs

-river straightening & dredging

-embankments

-flood relief channels

38
Q

what are soft engineering strategies

list the 4 soft engineering strategies

A

takes a more sustainable & natural approach to managing river flooding

-flood warnings and preparations
-floodplain zoning
-planting trees
-river restoration

39
Q

explain dams/reservoirs
gives advantages
give disadvantages

A

dam traps water, which builds up behind it, forming a reservoir. Water is released in a controlled way.

Advantages:
-Hydro-electric power
-water sports attract tourists
-creates wetland habitats

Disadvantages:
-Very expensive
-reservoir silts up which reduces storage capacity
-locals are displaced
-Habitats destroyed

40
Q

explain river dredging/straightening
gives advantages
give disadvantages

A

Straightening the river speeds up water so high volumes of water can pass through an area quickly. Dredging deepens the river so it holds more water.

Advantages:
-More water held in the channel
It can be used to reduce flood risk in built-up areas.

Disadvantages:
-expensive
-faster water flow increases flood risk

41
Q

explain embankments
gives advantages of
give disadvantages of

A

Raising the banks of a river means that it can hold more water.

Advantages:
-more water can be hold
-create walkways for locals .

Disadvantages:
-expensive
-Looks unnatural

42
Q

explain flood relief channels
gives advantages
give disadvantages

A

The floodwater flows into the relief channel is taken to an area where it’s absorbed, or re-enters the river

Advantages:
-Removes excess water from the river channel
-recreation-walking, fishing
-aquatic habitats created

Disadvantages:
-Expensive to build
-can look unattractive
-regular maintenance needed

43
Q

explain flood plain zoning
gives advantages
give disadvantages

A

restricts land uses in high-risk areas, high-value land uses away from flood-prone areas.

Advantages:
-expensive buildings & land uses are far from the river, so have a reduced flood risk.
-so less damage is caused, leading to fewer insurance claims.

Disadvantages:
-restricts economic development in areas as land use is prohibited

44
Q

explain flood warnings and preparation
gives advantages
give disadvantages

A

EA issues online warnings about floods so people can evacuate

Advantages:
-gives time to evacuate and prepare
-possessions can be saved, fewer insurance claims.

Disadvantages:
-Some people may not be able to access the warnings.
-Flash floods- too quick too prepare for
-does not stop floods

45
Q

explain planting trees
gives advantages
give disadvantages

A

trees intercept rainfall, reduces runoff

advantages:
-creates habitats
-reduces carbon emissions
-inexpensive

disadvantages:
-reduces biodiversity
-loss of farmland

46
Q

explain river restoration
gives advantages
give disadvantages

A

restores straightened channels to meandering pattern to slow water flow.

advantages:
-restores wetland areas
-reduces downstream flooding

disadvantages:
-expensive to construct and maintain

47
Q

Jubilee river

A

a flood relief channel on the River Thames, built in 2002
12km in length
50m wide
low flow conditions
removes excess water from thames

48
Q

Jubilee river social issues

A

-protection of wealthy properties such as windsor, but not less affluent towns downstream

-paddle boaters are disrupted by weirs

49
Q

Jubilee river economic issues

A
  • cost £110 million
    -floods damaged weirs- high maintenance cost
50
Q

Jubilee river environmental issues

A

-flooding in 2014 damaged habitats
-concrete weirs are unattractive
-algae collects above weirs

51
Q

describe the path of the river tees

A

River Tees is located in north of England.

The source of the River is located in the Pennines

river flows east to its mouth where it joins the North Sea

52
Q

describe the upper course of the river tees

A

-Hard, impermeable rocks.
-interlocking spurs (cauldron snout)
-Vertical erosion formed a V-shaped valley.
-High Force (UK’s largest waterfall)
-area of hard rock, called
Whinstone is located above soft rock (limestone)

53
Q

describe the middle course of the river tees

A

As the River Tees erodes sideways (lateral erosion), it forms meanders.
These are seen in the middle course near Barnard Castle.

54
Q

describe the lower course of the river tees

A

-Near Yarm, meanders are larger, oxbow lakes have formed.
-levees have formed when the river has flooded.
-a very large estuary with mudflats and sandbanks which supports wildlife in the area.
Sites such as Seal Sands are protected areas.

55
Q

define relief

A

the difference in heights of land’s surfaces

Geography (15 decks)

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