Chapter 8 - River Action: The Work Of Rivers

Question 1

What is a ‘watershed’?

Answer 1

The lines dividing a river and its tributaries (river basin) from those of another river and its tributaries (another river basin).

Question 2

What are ‘tributaries’?

Answer 2

Small rivers that join a larger river.

Question 3

What is a ‘confluence’?

Answer 3

The place where a tributary joins the main river.

Question 4

What is an ‘estuary’?

Answer 4

The tidal mouth of a river.

Question 5

What are ‘deltas’?

Answer 5

Land that forms at the mouth of a river.

Question 6

What is the ‘mouth’ of a river?

Answer 6

Where the river enters the sea or lake.

Question 7

What are distributaries?

Answer 7

Small rivers that break off from the main river as it enters the sea.

Question 8

What is the ‘basin’ of a river?

Answer 8

Area that is drained by the river and its tributaries.

Question 9

What is the ‘source’ of a river?

Answer 9

The place where the river begins.

Question 10

What is the ‘course’ of a river?

Answer 10

The path of the river from source to mouth.

Question 11

What are the forms of river transportation?

Answer 11

Solution, saltation, suspension and traction.

Question 12

What is ‘solution’?

Answer 12

Rock minerals are dissolved in the water and carried away.

Question 13

What is ‘saltation’?

Answer 13

Small stones are bounced along the bed of the river.

Question 14

What is ‘suspension’?

Answer 14

Light materials such as silt are transported in the water.

Question 15

What is ‘traction’?

Answer 15

Larger rocks are rolled along the river bed.

Question 16

What is an oxbow lake?

Answer 16

Am oxbow lake is a curved shape of water formed when a meander in a river is cut off leaving the river to straighten its course. Examples: Rover Moy, Co Mayo. Mississippi River, USA.

Question 17

How are oxbow lakes formed?

Answer 17

1. A river forms a meander.
2. The river erodes the land on the outer bends.
3. He river deposits on the inner bends.
4. During a flood the river breaks through to straighten its course.
5. The meander is cut off from the river to form an oxbow lake.
   Eventually it will dry out, leaving the shape of the old lake in the landscape.

Question 18

What is a levee?

Answer 18

A raised bank of earth running along the side of the river. Examples: River Moy, Co Mayo. Mississippi River, USA.

Question 19

How are levees formed?

Answer 19

1. The river floods and covers the floodplain.
2. The river deposits sediment (silt) as it slows down.
3. The faster-flowing water of the river channel comes in contact with the slower-flowing water of the floodplain along the bank of the river resulting in silt being deposited.
4. More silt is deposited along the riverbank then on the floodplain, forming a raised bank called a levee.

Question 20

What is a delta?

Answer 20

Low-lying land that forms at the mouth of rivers when the enter a lake or the sea. Examples: Mississippi River, USA. Nile River, Egypt.

Question 21

What are the features of a river?

Answer 21

Watershed, tributaries, confluence, estuary, delta, mouth, distributaries, basin, source, course.

Question 22

How are deltas formed?

Answer 22

The river slows down as it enters the lake or sea and deposits its load to build a delta. The delta forms when the sea currents are not strong enough to remove the silt.

Question 23

What is a dam?

Answer 23

A dam is a barrier built to hold back the flow of a river. Dams are built to produce electricity and act as reservoirs to store water.

Question 24

Name 3 advantages of dams.

Answer 24

1. Hydroelectricity is produced for homes and industries witch creates no pollution.
2. Water is stored in the reservoir behinds the dam.
3. The lakes behinds dams are used for recreation, such as boating & fishing on Blessington Lake, Co Wicklow.

Question 25

Name 3 disadvantages of dams.

Answer 25

1. Farmland is flooded when the lake behinds the dam is being made.
2. There is a danger of the dam collapsing or overflowing, endangering people living downstream.
3. People in the valley have to be moved elsewhere.