2.2 Rivers Flashcards

1
Q

Drainage basin

A

Area of land drained by a river

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2
Q

Watershed

A

Edge of highland making the boundary between two drainage basins.

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3
Q

Confluence

A

A point at which two rivers join

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4
Q

Source

A

The beggining of a river (normally at the mountains)

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5
Q

Tributary

A

Smaller river which joins a larger river

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6
Q

Mouth

A

Point where the river comes to an end (usually entering the sea)

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7
Q

Bed

A

The bottom of the river channel

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8
Q

Bank

A

The sides of the river channel

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9
Q

Width

A

Distance between two banks

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10
Q

Depth

A

Distance from water surface to the bed

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11
Q

Speed of flow

A

How fast the water in a river is moving

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12
Q

Wetted perimeter

A

Area of beds and banks in contact with the river

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13
Q

Channel

A

The route course that a river flows.

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14
Q

Thalweg

A

Fastest part of the river, in the middle of the channel, where there is least friction.

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15
Q

Attrition

A

Particles collide and break into smaller pieces. Normally at higher part of a river.

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16
Q

Hydraulic action

A

Force of the river erodes material from its banks and bed.

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17
Q

Abrasion

A

Particles rub against the river banks and bed (low part of river)

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18
Q

Solution

A

Acid in rivers dissolve rocks.

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19
Q

Traction

A

Rolling stones along the bed

20
Q

Saltation

A

Material bounces along the river bed

21
Q

Suspension

A

Small particles float and are carried with the water flow.

22
Q

Solution

A

Material dissolved in water (e.g. minerals)

23
Q

When does deposition occur?

A

When a river lacks the energy to carry its load.

24
Q

What type of material is first deposited?

A

Heavy material

25
Describe the upper course of a river (2)
Steep sided v-shaped valley | Thin river channel
26
Describe the middle course of a river (3)
V-shaped valley remains with a wider floor. River begins to meander Wider and deeper channel
27
Describe the lower course of a river (4)
Wide, shallow valley Large flood plains Large meanders Wide, deep, smooth sided channel
28
Potholes
Holes eroded in the solid rock of a river channel.
29
How are meanders created?
The river is fastest at the outside of a bend. | The river keeps eroding the outside while it deposits material in the inside (slip-off slope).
30
How are waterfalls created? (4)
River slowly erodes hard rock in the bed. Beneath it, a softer rock is eroded faster to form a step. Water erodes the bottom of the waterfall to create a plunge pool. The hard rock gets undercut as the soft rock erodes so that it collapses.
31
How is an ox-bow lake created? (3)
The neck of a meander comes very narrow. During high flow, the river cuts through the neck. Deposition occurs at the bank of the river so that an ox-bow lake is created.
32
How are levees created? (3)
River floods Material is deposited in the banks of a river. This forms a natural embankment (levees)
33
How are deltas created? (3)
River that carries large amounts of sediment meets the sea. It looses energy and drops the sediment. The river mouth becomes choked with sediment and slits into distributaries
34
How are flood plains created? (2)
Meanders create a wide valley floor | Material is deposited in the slip-off slopes, building a flood plain.
35
Causes of river flooding (5)
``` Steep-sided channel (surface run-off) Lack of vegetation (no interception) Impermeable rock (no percolation) Urban area (overland flow) Soil erosion (goes into rivers and reduce the amount of water it can carry) ```
36
Advantages of flooding (3)
Recharges groundwater stores Alluvium deposited in the floodplain is good for farming. Pollutants are washed off of land.
37
Disadvantages of flooding (4)
People can be killed Homes can be destroyed Infrastructure damaged Water borne diseases
38
How does a dam prevent flooding
Water is held back by a dam in a reservoir | Water is released in a control way
39
Disadvantages of dams (3)
Expensive Can damage the environment Can cause erosion downstream
40
How does afforestation prevent flooding
Trees are planted near the river There's greater interception This results in a lower river discharge.
41
Advantages of afforestation (2)
Low cost | Enhances environmental quality of drainage basin
42
How does river engineering prevent flood (3 ways)
Channel is made bigger to carry more water Channel is straightened so water travels faster Course altered to divert floodwater
43
Disadvantage of river engineering
Greater risk of flooding downstream
44
How does managed flooding prevent flooding.
Allow the river to flood naturally in some places, in order to prevent flooding in certain areas.
45
How does planning prevent flooding
Government introduce policies to control urban development near a flood plain.