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Geomorphology Flashcards

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1
Q

Define a drainage basin

A

The bowl-shaped depression from which water drains off the land.

Area occupied by a river system

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2
Q

What flows in a drainage basin?

A

A river system or stream network

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3
Q

What is a river system/stream network made up of?

A

A number of individual stream channels that join together

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4
Q

What are tributaries?

A

Rivers that join the main stream

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5
Q

What is the confluence?

A

The point where one river flows into another river in the drainage basin

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6
Q

What is a watershed?

A

The high ground that separates one drainage basin from the drainage basin that lies alongside it

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7
Q

The size and shape of a drainage basin is dependent on…

A

The position of the watershed

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8
Q

What is an area of high ground that separates tributaries?

A

A spur or interfluve

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9
Q

Define the mouth of a river

A

Where the river ceases to flow as it flows into a lake or the sea

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10
Q

Define the catchment area

A

The area of land that “catches” the rain that falls and that supplies water to a river system

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11
Q

What is the main source of water that reaches a drainage basin?

A

Precipitation - mainly rainfall

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12
Q

What is interception

A

When water is intercepted by the vegetation

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13
Q

what is retention?

A

when water is retained on teh surface

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14
Q

What is evaporation?

A

when water evaporates back into the atmosphere

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15
Q

what is evapotranspiration

A

when water is given off by plants and then evaporates

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16
Q

What is infiltration

A

when water seeps into the ground

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17
Q

What 5 things can occur when precipitation doesn’t become runoff?

A

interception

retention

evaporation

evapotranspiration

infiltration

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18
Q

What is surface runoff?

A

precipitation that is not intercepted, retained, evaporated or infiltrated which flows on the surface of Earth

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19
Q

What two kinds of surface runoff are there?

A

Overland flow (sheetflow) - water that flows across the land after rain

Channel flow (streamflow) - water that flows in distinct channels called streams or rivers

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20
Q

What is groundwater?

A

Water that seeps underground

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21
Q

what is groundwater that seeps through the soil?

A

throughflow

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22
Q

what is groundwater that seeps into river

A

baseflow

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23
Q

What will happen (to any precipitation) if there is a steep gradient on the land?

A

more runoff and less infiltration

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24
Q

Define permeable rock

A

rock that has pores or spaces through which water can pass

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25
Q

In what kind of soil will there be less runoff and more infiltration?

A

In porous soil

In unsaturated soil

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26
Q

What will happen (in terms of runoff and infiltration) if evaporation rates are high?

A

There will be more runoff and infiltration

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27
Q

What will happen (in terms of runoff and infiltration) if rainfall is high?

A

There will be more runoff and infiltration

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28
Q

What type of rainfall causes a lot of runoff?

A

Heavy thunderstorms

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29
Q

What type of rainfall results in a lot of infiltration?

A

Soft gentle rainfall

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30
Q

What is the difference between permeability of rocks and the resistance of rocks?

A

Permeability: Degree to which water moves through rocks

Resistance: relates to how easily the rock can be weathered and eroded

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31
Q

What are porous rocks?

A

Rocks that have many linked pores so that the water can move through the rocks

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32
Q

Describe the water-holding characteristics of sandstone

A

Porous rock

Therefore, permeable

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33
Q

Describe the water-holding characteristics of shale and clay

A

Not porous

Therefore, impermeable

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34
Q

Describe the water-holding characteristics of granite

A

impermeable - unless it has cracks and joints in it

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35
Q

Describe the water-holding characteristics of dolerite

A

Dolerite dykes are impermeable

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36
Q

What happens once groundwater infiltrates through the soil?

A

It percolates through permeable rocks until it comes to a layer of impermeable rock

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37
Q

What happens in the pores and cracks of the permeable rock?

A

Water collects here

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38
Q

What is the water table?

A

The upper level of the saturated rock beneath earth’s surface

It can be interpreted as the dividing line between the permanently wet layer of rock and the dry area above it

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39
Q

define an aquifer

A

rocks that hold water

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40
Q

what are aquicludes?

A

rocks that do not allow water to enter them

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41
Q

The water table is closer to the surface of the land in….

A

the wet season

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42
Q

Water percolates through permeable rock but ___ through soil

A

infiltrates

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43
Q

What shape does the water table take on?

A

The shape of the land.

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44
Q

What happens when the water table intercepts the surface at rivers and springs?

A

groundwater reaches the surface

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45
Q

How do people access groundwater?

A

By sinking boreholes

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46
Q

what is the type of river dependent on?

A

the height of the water table beneath the earth’s surface

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47
Q

What determines whether a river recieves baseflow or not?

A

The level of the water table in relation to the bed of the river

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48
Q

What is the cheif factor that determines the level of the water table?

A

the annual rainfall

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49
Q

What is baseflow?

A

The groundwater that seeps into the river

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50
Q

Where are permanent rivers found?

A

On the S and E coasts of SA

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51
Q

What are Two characteristics of a permanent river?

A
  1. the river flows all year
  2. water table always lies above the bed of the river so groundwater always seeps into the river
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52
Q

Where are periodic rivers found in SA?

A

In the interior

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53
Q

What are TWO characteristics of periodic rivers

A

the river flows only in the rainy season

the water table lies above the bed in rainy season but below the bed in the dry season

Consequently, the groundwater only seeps into the river in the rainy season

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54
Q

Where are episodic rivers found in SA?

A

In the western parts of SA

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55
Q

Name TWO characteristics of an episodic river

A
  • flows only after heavy rain
  • water table always lies below the riverbed
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56
Q

Which is the only exotic river in SA?

A

The Orange River

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57
Q

Name two characteristics of an exotic river

A

source of river in area with great deal of rain

river is supplied with groundwater only where it rises

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58
Q

Where will water erode a river channel?

A

Where the gradient is steeper and the rock is more easily eroded

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59
Q

What does the drainage pattern of a river system in a drainage basin show?

A

The arrangement of channels in relation to one another

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60
Q

What two things is the drainage pattern usually related to?

A

topography (shape of land)

geology (rock structure) of the area

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61
Q

Describe the dendritic drainage pattern

A

tree-shaped

tributaries join at acute angles

distinct interfluves are present

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62
Q

What conditions are required to attain the dendritic drainage pattern?

A
  • Rock uniformally resistant to erosion
  • Horizontal sedimentary / massive igneous rock
  • uniform slope

This pattern is not dependent on either the topography or the geology of the area

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63
Q

Describe the trellis drainage pattern

A
  • tributaries are short
  • tributaries meet the main stream at right angles
  • it is a longitudinal pattern
  • rivers cut gaps or poorts through the ridges formed by the hard rock
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64
Q

What conditions are required for the trellis drainage pattern?

A
  • alternate layers of hard and soft rock
  • parallel ranges of fold mountains
  • strong main stream

This pattern is dependent on both the topography and geology of the area

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65
Q

What are some of the charateristics of the rectangular drainage pattern?

A
  • the surface water flows in the exposed joints
  • tributaries join one another at right angles
  • there are right-angled bends in the individual streams
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66
Q

What are the required conditions to form the rectangular drainage pattern?

A
  • It occurs if there is well-jointed igneous rock such as granite in the area.

This pattern is determined by the geology of the area (not the topography)

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67
Q

What is another word for a radial drainage pattern?

A

centrifugal

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68
Q

What are is one characteristic of the radial/centrifugal drainage pattern?

A

Streams radiate outwards from a central high-lying area

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69
Q

What are the conditions required to develop a radial/centrifugal drainage pattern?

A
  • Develops on dome-shaped features

This pattern is dependent on the topography but not the geology of the area

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70
Q

What is one characteristic associated with the centripetal drainage pattern?

A

Streams flow inwards towards the central depression

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71
Q

What are the conditions required for the centripetal drainage pattern?

A
  • It develops around a low-lying area such as a depression or swamp

This pattern is dependent on the topography but not the geology of the area

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72
Q

What are some characteristics of teh deranged drainage pattern?

A

It is a haphazard pattern

There are many lakes and swamps

There are a few short streams

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73
Q

What are some of the conditions required for a deranged drainage pattern?

A
  • It is found in either a geologically young area or in an area that has experienced glaciation.

Both topography and geology have no influence on this pattern

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74
Q

What are some of the characteristics of a parallel drainage pattern?

A

Rivers flow parallel to each other

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75
Q

What are some of the conditions required for a parallel drainage pattern?

A
  • Where rivers form in areas of uniform gradient

This pattern is governed by only the topography of the area

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76
Q

What does drainage density indicate?

A

The amount of runoff in the drainage basin system

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77
Q

What can the density of the stream network be described as?

A

LOW

MEDIUM

HIGH

VERY HIGH

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78
Q

What doers it mean if the drainage density of a river is low?

A

There are very few streams forming the network of one drainage basin

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79
Q

How can you calculate the drainage density of an area?

A

Total length of the streams in the drainage basin (KM) / Total area of the river basin (KM2)

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80
Q

What else can be used to describe drainage density?

A

Texture

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81
Q

What are four ways that the texture of the drainage basin can be described?

A

coarse

medium

fine

superfine

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82
Q

Does a low-density network have a fine texture?

A

No, it has a coarse texture

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83
Q

Why does drainage density vary?

A

When there is a high runoff (same factors that determine amount of runoff and infiltration)

Rock resistance (stream channels form more easily if the rock is less resistant)

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84
Q

What does stream order indicate?

A

The degree to which the channels are linked in the stream network.

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85
Q

Will the main stream flowing out of a drainage basin with a high drainage density have a high or low stream order value?

A

High stream order value

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86
Q

Define the discharge of a river

A

The amount of water passing a point in a certain amount of time

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87
Q

What is the discharge of a river measured in?

A

Cumecs

This means Cubic metres per second

Can also be measured in centimetres per second

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88
Q

Name some characteristics of laminar flow

A
  1. Riverbed is level and even
  2. water flows in layers
  3. greatest speeds occur just below the surface
  4. speeds reached are greater
  5. less erosion (lower layers of water protect the river channel)
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89
Q

Name some characteristics of turbulent flow in a river

A
  1. Uneven and steep
  2. water continually changes levels
  3. flows with a bubbling action
  4. much erosion takes place (sand particles are lifted by the water)
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90
Q

Where does a river rise?

A

At its source

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91
Q

Give four processes that a river performs as it flows towards the sea

A
  • erodes land
  • transports eroded material (called load)
  • water must move in the channel
  • river may deposit its load
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92
Q

What are the processes performed by the river dependent on?

A

The energy of the river

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93
Q

When does a river has lots of energy and when does a river have little energy?

A

Lots of energy - when river is flowing fast

Little energy - when river is flowing slowly

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94
Q

Why does the river flow fastest just below the surface (described as “in the centre”)?

A

This is where there is the least friction

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95
Q

What is the rate (speed) at which the water flows dependent on?

A

Gradient

Volume

Channel shape

Channel roughness

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96
Q

Why do rivers with a large volume flow faster?

A

As less water is slowed down by friction

97
Q

Why can deeper channels achieve greater speeds of river flow?

A

There is less friction

98
Q

Why will a rough river channel flow slower?

A

There will be more turbulence and therefore less speed

99
Q

What is the stream capacity?

A

The maximum load that the stream can transport in relation to:

  • speed
  • volume
  • size of particles
100
Q

A river that flows quickly and has great volume is able to ___ as it has a large stream capacity.

A

carry a greater load

101
Q

What are the FIVE ways in which a river’s load can be transported?

A

flotation

solution

suspension

saltation

traction

102
Q

What is floation of a river’s load?

A

When very fine particles float on the surface of the water and are moved downstream

103
Q

What is the flotation load made up mostly of?

A

Leaves and twigs

104
Q

Describe what it is when particles making up a river’s load are transported in solution

A

Minerals are dissolved in the water and carried in this way.

A solution load is invisible

105
Q

What is it when particles making up a river’s load are transported in suspension?

A

When smaller particles of sand and silt are suspended in the water and moved by the water

106
Q

Suspension load causes a river to be…

A

muddy

107
Q

What is saltation?

A

When pebbles bounce along the riverbed

108
Q

What is traction?

A

When heavy, large boulders are rolled, pushed or bumped along the riverbed

109
Q

What makes up the bedload of a river?

A

The saltation load

AND

The traction load

110
Q

Why does a river need energy?

A

To carry the load

To overcome friction

To flow

111
Q

What will happen if a river has excess energy?

A

The river will erode the channel

112
Q

What does the rate at which erosion in a river occuring depend on?

A

How much excess energy the river has

The resistance of the rocks that make up the channel

113
Q

What is erosion by hydraulic action?

A

When the channel is eroded by the force of the water pounding on th erocks that form the sides and the bed of the channel

114
Q

What is river erosion by abrasion?

A

When eroded material carried by the water scrapes against the sides of the channel, causing the channel to be worn away

115
Q

What is pothole scouring?

A

When larger particles swirl in hollows on the river bed and make them larger

116
Q

What is attrition (in terms of river erosion)?

A

When small particles bump against one another, becoming smoother and rounder

117
Q

What is corrosion (in terms of river erosion)?

A

When acids in the water cause the rock that makes up the channel to dissolve

118
Q

What is river erosion by undermining?

A

when the banks are undercut by the force of the water

119
Q

What is headward erosion?

A

When the channel becomes longer as erosion towards the source of the river occurs

120
Q

What is vertical erosion?

A

When the river channel becomes deeper as erosion of the bed occurs

121
Q

What is lateral erosion?

A

When the channel becomes wider as the sides of the channel are eroded

122
Q

Is there lots of energy for erosion down the steep slopes of a mountain? Why / why not?

A

There is little excess energy for erosion because there is lots of friction:

  • Small volume
  • Small narrow channel
123
Q

What is responsible for the erosion of the sides of a valley?

A

mass wasting and sheetflow

NOT erosion by the river

124
Q

What is a longitudinal profile?

A

a diagram that shows the length of a river’s course from its source in the mountains to its mouth at sea level

125
Q

what type of river profile indicates the gradient down which the river flows?

A

longitudinal profile

126
Q

What shows the shape of a river valley at an imaginary line drawn across the river valley?

A

The transverse profile

OR

The cross profile

127
Q

Where the gradient is steep as indicated by the longitudinal profile, the valley shape is…

A

a narrow V-shape

128
Q

What 3 stages can the COURSE of the river be divided into?

A

Upper course

Middle course

Lower course

129
Q

What type of cross profile will form if the river has a lot of energy to erode downwards?

A

A deep, narrow steep-sided profile

130
Q

A river can have different cross profiles along its course, depending on….

A

the climatic and geological conditions of the area through which it is flowing

131
Q

Hydraulic action and abrasion result in ___ and ___ in the middle course of a river (where it has a more open V-shaped profile)

A

lateral erosion and undermining

132
Q

What two processes can lower the valley sides?

A

sheetflow and mass wasting

133
Q

What can the very flat, open V-shaped valley in the lower course of a river also be called?

A

the flood plain

134
Q

A river that has a straight course will have a ___ cross profile

A

symmetrical

135
Q

A meandering river will develop a ___ cross profile. This is because the erosive force of the water tends to be stronger on the ourside of the meander.

A

asymmetrical

136
Q

Is the cross profile of a river always similar to that of the valley in which it is found?

A

No

137
Q

What shape are most channel cross profiles?

A

Rectangular in shape

138
Q

What is the steep bank of a river called (when looking at the cross profile)

A

river cliff

OR

undercut bank

139
Q

What is the gently-sloped bank of a river called (when looking at the cross profile)

A

slip-off slope

140
Q

The longitudinal profile is the visual representation of the ___ and ___ of the river

A

height and length

141
Q

The sea is the ___ of the river as this is the lowest level to which a river can erode the landmass

A

permanent base level

142
Q

What kind of base levels are found along a river’s course?

A

Tempory/Local base levels

143
Q

What is a temporty base level?

A

Any factor present that interrupts the vertical erosion of the river

144
Q

Why is a temporary base level regarded as temporary?

A

Eventually the river erodes through the resistant rock

145
Q

What does “fluvial” mean?

A

relating to a river

146
Q

What type of erosion deepens the valley?

A

Vertical erosion

147
Q

What forms as the river twists and turns round obstacles of hard rock?

A

Interlocking spurs form

148
Q

What type of erosion gradually widens the valley floor?

A

lateral erosion

149
Q

Does lateral erosion begin on the concave or convex banks of river bends?

A

Concave banks of river bends

150
Q

What happens once the end of a spur is cut off by lateral erosion?

A

a truncated spur forms

151
Q

What is a gorge?

A

A very deep, steep-sided valley formed by an energetic rover in a humid environment

152
Q

What is a canyon?

A

A very deep, steep-sided valley formed by an exotic river in an arid environment.

Found in an area of horizontal rock strata of varied resistance to erosion

153
Q

What is the difference between a canyon and a gorge?

A

A gorge is found in a humid environment

A canyon is found in an arid environment

154
Q

How do waterfalls and rapids form?

A

By a resistant layer of rock across the course of the river, leading to a sharp change in the gradient

155
Q

What determines whether a waterfall or rapid will form?

A

The angle at which the resistant rock layer dips

156
Q

What is the resistant layer of rock which forms a waterfall sometimes referred to?

A

fall-maker

OR

lip of the waterfall

157
Q

What causes the position of a waterfall to move upstream?

A
  1. The undercutting of the softer rock beneath the lip
  2. the lip collapses
158
Q

What often occurs downstream of a waterfall? Why?

A

A deep gorge often forms downstream of a waterfall.

This is because the headward erosion results in the formation of a deep gorge downstream of the waterfall

159
Q

What is the name for deep, circular depressions or hollows on the bed of a river?

A

potholes

160
Q

How are potholes formed?

A

When pebbles collect in depression on the bed of the river.

Through abrasion and pothole scouring, the depressions become deeper

161
Q

What can cause the flow of a river to slow down?

A

a reduction in the gradient

Eg) when the river flows off the mountatin onto the plain downstream

162
Q

What can cause the load of a river to increase?

A

Deforestation causes increased erosion of topsoil in the drainage basin.

163
Q

What is the name of the fertile material deposited by a river?

A

Alluvium

164
Q

What 4 situations can cause a river to deposit its load?

A
  1. Speed of river decreases (reduction in gradient of river)
  2. Volume of water decreases (usually after a flood)
  3. Channel of river becomes wider (flowing on floodplain)
  4. When load of river increases (deforestation)
165
Q

What can form at the base of mountains when a river that is carrying a lot of sediment flows onto the flatter plain?

A

alluvial fans

166
Q

Sediment of an alluvial fan is deposited in what shape?

A

In the shape of a fan

167
Q

The river splits into ___ as a result of an alluvial fan

A

distributaries

168
Q

What are distributaries

A

smaller streams leading from the main stream to flow round the deposited material of an alluvial fan

169
Q

What are raised banks of a river in its lower course called? Why do they form?

A

levees

They form from the deposition of coarse material as the river flows over the sides of the channel when it floods

170
Q

What can form from the water that lies on the floodplain?

A

back swamps

171
Q

What forms when a river breaks through the neck of a meander when it is in flood, causing the meander loop to be cut off from the main stream?

A

An ox-bow lake

172
Q

What forms once an ox-bow lake dries up?

A

A meander scar

173
Q

What is it called when a river bends and winds across the floodplain?

A

a meandering channel pattern

174
Q

What lies just above the bedrock in the lower course of a river valley?

A

alluvium (deposited fertile material)

175
Q

What are the raised areas at the edge of the flooodplain that are the remains of the old valley sides called?

A

bluff

176
Q

What is a tributary that flows alongside the river until it is able to flow into the main stream where there is a break in the levee called?

A

a yazoo stream

177
Q

Where does depostion occur and where does erosion occur in the cross section of a river?

A

Erosion - outer bank

Deposition - inner bank

178
Q

What is a channel pattern?

A

The pattern made by a single channel

179
Q

What is the difference between a channel pattern and a drainage pattern?

A

A channel pattern is the pattern made by a single channel

A drainage pattern is the pattern made by the way in which individual channels join one another

180
Q

How does a delta form?

A
  1. River slows down as it enters the sea
  2. deposits its load at the mouth of the river
  3. deposited sediment at the mouth of the river forms a delta
181
Q

When a delta forms, which particles are deposited first and which particles settle further out to sea?

A

Heaviest particles are deposited first and the finer particles settle further out to sea

182
Q

Describe the land which makes up a delta

A

Flat, fertile land

183
Q

What does the river split up into in order to flow through the delta?

A

Distributaries

184
Q

What shape is a arcuate delta?

A

Shaped like a fan

185
Q

What shape is a digitate delta?

A

Look like birds’ feet

186
Q

What shape is a cuspate delta?

A

Shaped like the cusps of teeth

187
Q

What shape is a estuarine delta?

A

It is formed in the funnel-shaped mouth of a river

188
Q

Define grade

A

When the gradient is just suffficient for the transportation of the load under existing volume and channel shape conditions.

This is when erosion rates are in equilibrium with deposition rates

189
Q

What shape of profile does a graded river have?

A

A smooth, concave-shaped profile

190
Q

What is a multi-concave profile?

A

When streams have graded and ungraded segments separated from each other by sharp gradient changes at tempory base levels

191
Q

What does grade depend on?

A

Stream load capacity

This, in turn, depends on:

  • velocity of river
  • volume of river
  • shape of river
  • nature of river
192
Q

What is an overgraded river?

A

When the load is less than the capacity

This means the stream can collect more material through erosion

This decreases the gradient and the speed becomes slower (only until stream capacity is reached and the river has achieved grade)

193
Q

What is an undergraded river

A

When the load is greater than the stream capacity

This makes the river deposit material

The gradeint becomes steeper and the river can transport a greater load

In this way, the river has graded itself

194
Q

What is a rejuvinated river?

A

Simply an overgraded river

195
Q

Define rejuventation

A

When a river gains renewed energy and erodes downwards again

196
Q

When can rejuvenation occur?

A
  1. If the gradient of the river increases
    1. drop in sea level
    2. uplift of the landmass
  2. If the volume of the river increases
    1. increased rainfall
    2. capture of another river
    3. incresed runoff due to the clearing of the vegetation
197
Q

Which FOUR landforms can form as a result of rejuvenation?

A

Incised (entrenched) meanders

waterfalls (at the knickpoint)

valleys within valleys

terraces

198
Q

What is it called when the position and gradient of a watershed is altered so that the gradient is the same on each side of the watershed?

A

Abstraction

199
Q

Where in SA is abstraction frequently occuring?

A

On the eastern side of the Drakensberg mountain range

200
Q

When does abstraction occur?

A

When the stream on one side of a watershed is more energetic than the stream on the other side of the watershed

201
Q

Describe the process of abstraction

A
  1. a more energetic stream erodes at a faster rate
  2. this lowers the watershed and moves it in the direction of the less energetic stream
  3. abstration stops when the gradients of both streams are the same
202
Q

Give 3 reasons why a river that erodes a watershed could be more energetic

A
  1. It might have been flowing down a steeper gradient
  2. It might have has a great volume (due to it being in an area with higher rainfall)
  3. It might have been flowing over less resistant rock
203
Q

What causes a more energetic river to increase the size of its drainage basin?

A

abstraction

204
Q

when does river capture occur?

A

When a river with more energy intercepts another river and “captures” the water of the other river

205
Q

What is the captor stream?

A

The river with more energy that captured another river

206
Q

What is a misfit stream?

A

the river that lost its headwaters

A misfit stream can also be called a beheaded stream

207
Q

What is the captive?

A

The river that was captured

208
Q

What is a wind gap?

A

The part of the old valley of the captured river that is now dry and filled with sand and gravel.

209
Q

Where does a knickpoint waterfall occur in terms of river capture?

A

At the point where the captured (captive) stream flows into the captor stream

210
Q

What can cause river capture?

A
  1. Headward erosion of the more energetic river (this can lengthen the channel upstream)
  2. Lateral erosion on the outer bend of a meandering river
  3. Abstraction of a watershed (the abstracting river can intercept the course of the river flowing down the other side of the watershed)
211
Q

What are the results of river capture?

A
  • Captor gains water
    • more energy
    • erosion take place at a faster rate
  • Misfit loses water
    • less energy
    • has to deposit much of its load
212
Q

Name some things that you can identify to help you see the point of river capture

A
  1. identify a sharp bend in one of the streams (this shows the elbow of capture)
  2. Look for a knickpoint waterfall close to the elbow
  3. Find the wind gap close to the elbow
  4. Identify the stream that flows down a steeper gradient
  5. try to recognise the misfit stream
213
Q

Rivers with superimposed and antecendent drainage patterns have river coursers that do / do not relate to the rock structures or topography of the area in which the river is flowing

A

do not

214
Q

In a superimposed drainage pattern, does the river avoid the resistant rock?

A

No, it has eroded a course through the mountains

215
Q

TRUE OR FALSE:

The course of a river (when associated with a superimposed drainage pattern) has a relation to the present geology and topography of the area

A

False,

The course of the river in a superimposed drainage pattern has no relation to the present geology and topography of the area.

216
Q

What rocks does a superimposed drainage pattern develop on?

A

On rocks that have since been removed by erosion

217
Q

Is a superimposed drainage pattern flowing on older or younger rocks that have been uncovered?

A

Older rocks that have been uncovered

218
Q

Are superimposed rivers younger than the structures over which they flow?

A

Yes

219
Q

What is a good example of a superimposed drainage pattern in SA?

A

The Vaal River near Parys

220
Q

Does a antecendent river develop its course on a former landscape?

A

Yes

221
Q

What has taken place in order for an antecendent drainage pattern to form?

A

Folding or faulting

222
Q

Does the stream of an antecendent river (where the landscape undergoes folding and faulting) maintain its course?

A

Yes

223
Q

How does the antecendent stream maintain its course along the river?

A

It erodes through the anticline at the same rate at which it is forming

224
Q

Are antecendent rivers younger than the structures through which they flow?

A

No, they are older

225
Q

Do antecendent rivers flow around the high-lying ground?

A

No, they cut poorts through the anticlines

226
Q

What is a good example of an antecendent river in South Africa?

A

The Orange River

227
Q

Define catchment area

A

The area that receives rainfall and supplies water to the river

228
Q

When will SA experience severe water shortages? What should we do about it?

A

2025

The management of catchment areas, drainage basins and rivers is therefore vital for people and the sustainable development of the country

229
Q

What is another reason for managing catchment areas, besides due to predicted water shortages?

A

To prevent floods that can cause major damage

230
Q

What are natural storage areas of water?

A

Wetland areas within the drainage basin

231
Q

Why do wetlands need to be conserved (in terms of management of catchment areas and drainage basins)?

A

They need to be able to release water slowly to supply rivers with water, also to filter the water, catching sediments and pollution

232
Q

How can people alter the flow characteristics and quality of rivers?

A
  • building dams, canalising rivers, cutting through meander loops and diverting river courses
  • implementing inter-basin transfer schemes
  • making use of wetlands for farming and draining wetlands for settlement
  • clearing the vegetation, which increases runoff and adds sediment to the river
  • allowing the spread of alien vegetration alongside rivers
  • polluting the river through refuse deposits, sewerage, setergents, chemicals
  • construction of impermeable tar and concrete surfaces
  • building on a river’s floodplain
233
Q

What is the main negative impact of alien vegetation?

A

It uses a lot more water

This makes it deplete the underground water supply

234
Q

How can people pollute a river?

A

refuse deposits

sewerage

detergents

chemicals

235
Q

How can people prevent or minimise flooding by rivers?

A
  1. Entire drainage basin must be studied
  2. Wetlands must be preserved
  3. dams must be correctly positioned
  4. meander loops can be cut through (allows the water to flow downstream quicker)
  5. conservation methods to reduce removal of vegetation
236
Q

What does RHP stand for? What does it aim to do?

A

River Health Programme

  1. It assesses the biological habitats of fish, aquatic organisms and river vegetation and the general health of rivers
  2. It then makes recommendations so that authorities can work towards managing rivers in order to achieve the desired health of the river
237
Q

Who controlls the implementation of the RHP?

A

The Department of Water Affairs and Forestry (DWAF)

Each province has a network of people and institutions involved in monitoring river health

238
Q

What does the term “riparian zone” refer to?

A

River banks

Geography (5 decks)

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