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rivers Flashcards

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1
Q

whats a tributary

A

a stream or river that joins a larger river

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2
Q

whats a drainage basin

A

area of land drained by a river system

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3
Q

whats a watershed

A

line of seperation between 2 river systems

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4
Q

whats a confluence

A

the point where 2 rivers meet

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5
Q

whats a interception

A

precipitation thats collected and stored by vegitation

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6
Q

whats infiltration

A

movement of water into a soil, rate at which water enters soil depending on intensity of rainfall,permeability of the soil and extent of water saturated in soil.

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7
Q

whats a throughflow

A

downslope movement of water into soil

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8
Q

whats abrasion (corrasion)

A

the wearing away of river bed by the sediment carried througha river

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9
Q

whats attriciton

A

wearing away of sediment as 2 particles colide and hit eachother to become smaller and rounder particles

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10
Q

whats hydraulic action

A

the force of air and water on cracks and sides of a river

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11
Q

whats groundwater flow

A

underground movement of water from the land to river

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12
Q

whats suspension

A

small particles held up by flow in the river

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13
Q

whats saltation

A

heavier particles bouncing along the river bed

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14
Q

whats soloution

A

when sediment dissolved in water

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15
Q

whats traction

A

when sediment is dragged or rolled along the river bed

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16
Q

how does the hydrologocal cycle start

A

when precipitation or condensation occurs and water gets inflitrated through soil then leaves the system during dischararge,evaporation or transpiration

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17
Q

whats the source of a river

A

area where the river begins

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18
Q

whats the mouth of a river

A

the area where a river meets the sea

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19
Q

what happens in the uppercourse of a river (4 features)

A

-gradient is at its peak
-sediment shape is large
-slow average velocity
-mainly transporation of sediment

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20
Q

what happens in the middle course of a river (4 features)

A

-sediment is broken up and smoother
-gradient is less steep
-mainly erosion occurs
-wide cross section

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21
Q

what happens in the lowercourse of a river (4 features)

A

-flat gradient
-super small sediment
-mainly deposition (discharge of minerals)
-very fast average velocity

22
Q

whatre the 3 features in the upstream of a river according to bradshaws model

A

-larger particles sizes
-channel bed is rough
-a steep gradient

23
Q

whatre the 5 features in the upstream of a river according to bradshaws model

A

-increase in discharge
-wider channel width
-inc in channel depth (due to water pressure pushing channel down)
-inc in sediment quantitiy
-increase in average velocity due to wwater buildup

24
Q

what does vertical erosion do

A

dominant in the upper course of rivers. It increases the depth of the river and valley, as the river erodes downwards

25
Q

what does lateral erosion do

A

dominant in the middle and lower course of rivers. It increases the width of the river and valley as it erodes sideways

26
Q

what are the 4 erosion processes

A

-Hydraulic action (water and air forces create cracks and damage river bed)
-Abrasion (sediment wears away river floors)
-Attrition (2 rocks colide and break eachother down)
-solution (sediment dissolves in water)

27
Q

what 5 factors increase erosion

A

-heavier and sharper load
-greater velocity and discharge
-steeper gradient
-soft rocks (more easily eroded)
-water acidity (inc solution)

28
Q

whatre the 4 processes of transporation

A

-Traction (larger rocks roll along river bed)
-Saltation (smaller material bounces along river bed)
-Suspension (lighter sediment carried by river flow)
-Solution (sediment dissolves)

29
Q

why does deposition occur

A

due to a decline in energy or velocity

30
Q

compare hydraulic action with abrasion

A

hydraulic action is the force of water and air on sides and cracks in rivers while abrasion is when large pieces of sediment erode the river bank

31
Q

whatre the 4 landforms created by uppercourse rivers

A

Waterfalls
Gorges
V-shaped valleys
Interlocking spurs

32
Q

what are the 2 main erosional processes in the formation of waterfalls

A

abbrasion and hydraulic action

33
Q

describe how a waterfall forms

A

-The soft rock erodes quicker, undercutting the hard rock and creating a plunge pool
-This leads to the development of an overhang of hard rock which eventually over time, collapses
-the overhang falls into the plunge pool increasing abrasion and making the plunge pool deeper
-The process then begins again and the waterfall retreats upstream leaving a steep sided gorge

34
Q

describe the formation of v shaped valleys

A
  • Vertical erosion is dominant in the upper course of the river
    -This cuts down into the river bed and deepens the river channel
    -Weathering and mass movement leads to material from the valley sides collapsing into the river forming a steep v-shaped valley
35
Q

describe the formation of interlocking spurs

A

-in the upper course of the river the channel starts to meander
-Erosion happens on the outside of the bend
-in the upland areas this forms interlocking spurs

36
Q

what are the 4 landforms created by the lower course

A

Meanders
Ox-bow lakes
Floodplains
Levees

37
Q

whats a floodplain

A
38
Q

how do meanders form

A

-in lowland areas lateral erosion is dominant
-Meanders increase in size
-The fastest water flow (thalweg) is on the outside of the river bends, leading to erosion:
-The erosion undercuts the riverbank forming a river cliff
-The riverbank collapses and the edge of the meander moves further out
-The slowest flow is on the inside of the river bends, leading to deposition:
-the deposits form a slip-off slope
-Deposition on one side and erosion on the other leads to the meander migrating across the valley

39
Q

how do oxbow lakes form

A

1- erosion and deposition form around ameander
2-increased erosion during floow conditions which exaggerates the meanders
3-river hreaks through during floods which causes firther depoisition which causes the meander to turn into an oxbow lake

40
Q

explain how waterfalls and gorges are formed (4)

A

waterfalls occur on horizonally bedded rocks,soft rock is undercut by hydraulic action and abrasion to form a plunge pool. softer rock is eroded by fractions of the harder rock that break off,weight of water and lack of support causes the waterfall to collapse and retreat which forms a gorge

41
Q

what is an impermeable rock

A

rock that does not allow liquid or gas to flow through it

42
Q

what is lag time

A

The time taken for river levels to rise after a storm

43
Q

when does flodding occur

A

When the amount of water exceeds the capacity of the river’s channel. The excess water overflows the river’s banks and spills out across the flood plain. It can occur as a result from persistent rain over a relatively long period of time.

44
Q

what are the 6 physical causes of flooding

A

1) Weather - Intense rainfall greater than the infiltration capacity of the ground. Prolonged rainfall leading to the satiation of the ground. Rapid snow melt as temperatures suddenly rise about freezing.
2) Rock - Impermeable rocks limiting percolation and encouraging rapid surface run off.
3) Soil - Low infiltration rate in certain soils (clays)
4) Relief - steeps slopes causing fast run off
5) Drainage Density - High drainage density means many tributary systems can carry the rainwater quickly to the main river.
6) Vegetation - Low density vegetation absorbs little water

45
Q

what are the 4 human causes of flooding

A

1) Deforestation - cutting down trees reduces interruption and speeds up run off.
2) Urbanisation - concrete and tarmac surfaces together with drains mean quicker delivery of rain water to the main river.
3) Agriculture - Risk of flooding increase by leaving soil bare.
4) Climate Change - Burning fossil fuels causes melting of ice sheets and glaciers as well as more rainfall and more frequent storms.

46
Q

how can rivers be used as an advantage

A

-the silt deposited during flooding is often rich in minerals and nutrients, making it ideal for growing crops
-Rivers are a source of food
-The floodplains are flat land which makes the construction and building of transport networks easier
-Water can be used to irrigate farmland
-Leisure and tourism
-Generating electricity
-Transporting goods and people

47
Q

whats a levee

A

A embankments on the sides of the river made from layers of sediment deposited from flooding.

48
Q

what do dams do

A

-reduce speed of water flow,control amount of water in a river,cause deposition behind dams,increase erosion downstream of the dam,change ecosystems,increase pressure on rocks and maaybe cause earthquakes

49
Q

how can we manage the impacts of flooding

A

-building dams to hold back excess water
-raising river banks
-create new flood relief channels

50
Q

whatre the hazards of floods and river erosion

A

-Flood waters may increase the spread of water related diseases;
-Deaths and injuries as floodplains are often densely populated due to the fertile soils
-Bridges and transport routes may be damaged or destroyed by the flood waters
-erosion of the river banks leads to the loss of farmland, housing and transport routes
-Destruction of crops
-Increased insurance costs
-Lower house prices

51
Q

Explain how a waterfall is formed on a river. You may use a labelled diagram or diagrams (5)

A

-Hard rock overlies softer rock / (passes over) hard then soft / alternating
hard and soft;
-Hard rock resists erosion / softer rock is eroded rapidly;
-Undercutting / overhang develops;
-Overhang collapses;
-Retreat of waterfall / process repeats;
-Specific named methods of erosion or description of it

52
Q

For a named river you have studied, explain the causes of flooding.(7)

A

-Heavy rainfall,
-Rainfall over a long period of time,
-Impermeable rocks,
-Rocks reach saturation level,
-Snow / ice melt,
-Deforestation,
-Urban development
-Storm surges
-High spring tides
-Cyclones – so coastal flooding idea fine at estuary
-Lack of river management

geography (9 decks)

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