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GCSE - Geography (Dave) > Rivers > Flashcards

Rivers Flashcards

1
Q

What percent of the worlds water is found in seas and oceans?

A

97%

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2
Q

What is a drainage basin?

A

The area of land drained by a river

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3
Q

What is the catchment area?

A

The area within the drainage basin

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4
Q

What is the watershed?

A

The boundary between two or more drainage basins

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5
Q

Where are watersheds usually found?

A

The edge of highlands surrounding a drainage basin

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6
Q

What is a confluence?

A

The point at which two rivers or streams join together

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7
Q

What is a tributary?

A

A stream or smaller river which joins a larger river

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8
Q

Describe a cross section of the land near to the source of a river

A

V-shaped valley Narrow and shallow river

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9
Q

What is the name of the process that causes a river to erode downwards?

A

Vertical erosion

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10
Q

Name the four main forms of erosion

A

Hydraulic action Solution Attrition Abrasion

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11
Q

Explain hydraulic action

A

The force of the river causes air to be trapped in cracks of the bank. This pressure weakens the banks and slowly causes them to wear away

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12
Q

Explain abrasion

A

Erosion caused by the rubbing of materials carried by rivers

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13
Q

Explain attrition

A

Erosion caused when rocks and boulders transported by rivers and waves bump into each other and get smaller

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14
Q

What does attrition do to the size of the rocks?

A

Smaller Smoother Rounder

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15
Q

Name the four different transport processes in rivers

A

Solution Suspension Traction Saltation

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16
Q

Explain solution for erosion and transportation

A

Small pieces of rock and minerals are dissolved in the river and then carried along

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17
Q

Explain suspension

A

Fine, light materials are carried along the water

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18
Q

Explain saltation

A

Small pebbles and stones bounce along the river bed

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19
Q

Explain traction

A

Larger rocks and boulders are rolled along the river bed

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20
Q

What is required for traction to occur?

A

High energy level in the river

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21
Q

Where are energy levels usually at their highest in a river?

A

In the lower course

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22
Q

What causes deposition?

A

The river losing energy : Inside of a meander

Estuary

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23
Q

Where is deposition the most common?

A

Near to the mouth Shallow areas Low volume of water

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24
Q

Name the upper course features

A

-V shaped valleys -Interlocking Spurs -Rapids -Waterfalls -Gorges

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25
Name the features of the middle course
-Wider, shallower valleys -Meanders -Oxbow lakes
26
Name the features of the lower course
-Wide, flat bottomed valleys -Floodplains -Levees -Deltas
27
Why do interlocking Spurs occur?
The river avoids areas of hard rock due to its low energy
28
How does a waterfall occur?
-A layer of hard rock above a thicker layer of soft rock causes the soft layer to erode faster -The soft rock slowly undercuts the hard rock due to it eroding faster and a steep edge is created -This overtime develops to be a waterfall as the height difference increases -Eventually the overhanging rock falls and the waterfall slowly retreats
29
How do Rapids form?
Ridges of hard rock cause an uneven slope. This creates Rapids
30
Why does water travel faster in the middle course compared to the upper course?
The channel has been widened and deepened and therefore less friction
31
Why do meanders form?
-The river erodes laterally -Deposition on inside -Erosion on outer side
32
What happens on the inside bend of a meander?
-The river flows slower -Material is deposited -More friction
33
What happens on the outside bend of a meander?
-Water erodes and undercuts the bank -Most energy -Less friction
34
What is the result of meanders being cut off?
An oxbow lake
35
When is an oxbow lake most to form?
In times of flood
36
What happens when oxbow starts to form?
-Sediment builds up, blocking it from the rest of the river -Over time the stagnant water could be replaced by land as sediment is deposited
37
What is it called when a meander is replaced by land?
Meander scar
38
What happens to interlocking Spurs if they occur in the middle course?
Bluffs (Truncated Spurs) are created
39
What are created by floods in the middle course?
Levees
40
What is the material which is deposited in the event of a flood?
Alluvium deposits
41
What is precipitation?
Rainfall
42
What is interception?
When trees and plants catch rainfall.
43
What is infiltration?
When water on the surface enters the ground.
44
What is percolation?
The gravity flow of water in soil.
45
What is infiltration?
When water on the surface enters the ground.
46
What is throughflow?
Sideways flow of water under ground.
47
What is transpiration?
The flow of water up a plant and, eventually, its evaporation.
48
What can cause flooding?
• A steep-sided channel • A lack of vegetation or woodland • A drainage basin, consisting of mainly impermeable rock • A drainage basin in an urban area • Heavy rainfall
49
What can cause river erosion?
• Stream bed lowering• Saturation of banks• Redirection and acceleration of flow • Removal or disturbance of protective vegetation • Bank soil characteristics such as poor drainage or seams of readily erodible material within the bank profile• Wave action generated by wind or boat wash;• Excessive or inappropriate sand and gravel extraction• Intense rainfall events (e.g. cyclones).
50
What are the advantages of living near a river or a delta?
• Fertile soil • Fishing • Tourism • Protection against hurricanes (only delta) • Sand and gravel for construction
51
What are the two main ways river flooding can be managed?
Hard-engineering Soft-engineering
52
What are some examples of hard engineering?
• Dams • River engineering
53
What are some examples of soft engineering?
• Afforestation • Managed flooding • Planning
54
What is the Bradshaw model?
A graphic representation of the change of characteristics as you go downstream
55
What is the cross section?
A profile of the shape of the river channel
56
What is the channel width?
The measuremeant from one bank to the other, either present flow or bankfull flow Increases going downstream
57
What is the mean depth?
Water's surface to the river bed across the entire width Increases going downstream
58
What is the discharge of a river?
Volume of water which flows past a point in a given time. Usually measured in cubic meters/second (cumecs) and increases going downstream
59
What is the wetted perimeter?
The surface of the channel bottom and sides in direct contact with water
60
What is the hydraulic radius?
Measure of a channel flow efficiency cross-sectional area / wetted perimeter Increases going downstream
61
How does the channel bed roughness change as you go downstream?
Decreases: due to ersosional processes which increase due to a higher discharge
62
How does turbulance and friction change as you go downstream?
Decreases: due to the smaller particle size
63
What is evaporation?
When water particles heat up to a point where they become a gas
64
What is the source?
The place where the river begins
65
What is the mouth of a river?
Where the main river meets the sea/ocean/lake
66
What is drainage denisty?
Total length of the rivers / area
67
What type of rock underlys high drainage denisty?
Non-porous hard rocks such as clay
68
What does high and low drainage density look like?
![]()
69
What drainage density is more likely to flood?
High Drainage density
70
What is groundwater flow?
Water flowing through rocks underground
71
What is surface storage?
Water which is stored in rivers, lakes reservoirs etc.
72
What is a rivers load?
The material which the river is carrying
73
What is a meander scar?
The feature left behind when the water in an ox-bow lake dries up
74
What are natural levees?
A raised river bank formed by deposition
75
What are man-made levees?
Artificial raised banks to increase the channel capacity and reduce flood risk
76
What is a floodplain?
An area of land around a river channel which is formed during times of flood when deposition occurs
77
Why is alluvium useful?
Rich with minerals and is essential for fertile lands
78
What is the bluff line?
Outer limits of the floodplain
79
What is the strand line?
Outer limit of floodplain where material is left
80
How is a delta formed?
A delta is formed when the river deposits its material faster than the sea can remove it
81
Name and give an example of 3 types of deltas
* Bird's foot delta (Mississipi) * Arcuate delta (Nile) * Cuspate delta (Ebro)
82
What is flocculation?
Salt from the sea causes the load from a river to join together and heavier so it is more likely to be deposited
83
What are the disadvantages of living near/on a delta?
* Risk of flood * Mosquitos (malaria, dengue) * Dirty and polluted water * Rising sea levels * Defences cost

GCSE - Geography (Dave) (16 decks)

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