2.2 Rivers

Question 1

Drainage basin

Answer 1

Area of land drained by a river

Question 2

Watershed

Answer 2

Edge of highland making the boundary between two drainage basins.

Question 3

Confluence

Answer 3

A point at which two rivers join

Question 4

Source

Answer 4

The beggining of a river (normally at the mountains)

Question 5

Tributary

Answer 5

Smaller river which joins a larger river

Question 6

Mouth

Answer 6

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

Question 7

Bed

Answer 7

The bottom of the river channel

Question 8

Bank

Answer 8

The sides of the river channel

Question 9

Width

Answer 9

Distance between two banks

Question 10

Depth

Answer 10

Distance from water surface to the bed

Question 11

Speed of flow

Answer 11

How fast the water in a river is moving

Question 12

Wetted perimeter

Answer 12

Area of beds and banks in contact with the river

Question 13

Channel

Answer 13

The route course that a river flows.

Question 14

Thalweg

Answer 14

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

Question 15

Attrition

Answer 15

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

Question 16

Hydraulic action

Answer 16

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

Question 17

Abrasion

Answer 17

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

Question 18

Solution

Answer 18

Acid in rivers dissolve rocks.

Question 19

Traction

Answer 19

Rolling stones along the bed

Question 20

Saltation

Answer 20

Material bounces along the river bed

Question 21

Suspension

Answer 21

Small particles float and are carried with the water flow.

Question 22

Solution

Answer 22

Material dissolved in water (e.g. minerals)

Question 23

When does deposition occur?

Answer 23

When a river lacks the energy to carry its load.

Question 24

What type of material is first deposited?

Answer 24

Heavy material

Question 25

Describe the upper course of a river (2)

Answer 25

Steep sided v-shaped valley

Thin river channel

Question 26

Describe the middle course of a river (3)

Answer 26

V-shaped valley remains with a wider floor.
River begins to meander
Wider and deeper channel

Question 27

Describe the lower course of a river (4)

Answer 27

Wide, shallow valley
Large flood plains
Large meanders
Wide, deep, smooth sided channel

Question 28

Potholes

Answer 28

Holes eroded in the solid rock of a river channel.

Question 29

How are meanders created?

Answer 29

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).

Question 30

How are waterfalls created? (4)

Answer 30

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.

Question 31

How is an ox-bow lake created? (3)

Answer 31

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.

Question 32

How are levees created? (3)

Answer 32

River floods
Material is deposited in the banks of a river.
This forms a natural embankment (levees)

Question 33

How are deltas created? (3)

Answer 33

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

Question 34

How are flood plains created? (2)

Answer 34

Meanders create a wide valley floor

Material is deposited in the slip-off slopes, building a flood plain.

Question 35

Causes of river flooding (5)

Answer 35

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)

Question 36

Advantages of flooding (3)

Answer 36

Recharges groundwater stores
Alluvium deposited in the floodplain is good for farming.
Pollutants are washed off of land.

Question 37

Disadvantages of flooding (4)

Answer 37

People can be killed
Homes can be destroyed
Infrastructure damaged
Water borne diseases

Question 38

How does a dam prevent flooding

Answer 38

Water is held back by a dam in a reservoir

Water is released in a control way

Question 39

Disadvantages of dams (3)

Answer 39

Expensive
Can damage the environment
Can cause erosion downstream

Question 40

How does afforestation prevent flooding

Answer 40

Trees are planted near the river
There’s greater interception
This results in a lower river discharge.

Question 41

Advantages of afforestation (2)

Answer 41

Low cost

Enhances environmental quality of drainage basin

Question 42

How does river engineering prevent flood (3 ways)

Answer 42

Channel is made bigger to carry more water
Channel is straightened so water travels faster
Course altered to divert floodwater

Question 43

Disadvantage of river engineering

Answer 43

Greater risk of flooding downstream

Question 44

How does managed flooding prevent flooding.

Answer 44

Allow the river to flood naturally in some places, in order to prevent flooding in certain areas.

Question 45

How does planning prevent flooding

Answer 45

Government introduce policies to control urban development near a flood plain.