Rivers

Question 1

Four processes of Erosion?

Answer 1

Attrition, Corrasion, Corrosion, Hydraulic Action

Question 2

Four processes of Transportation?

Answer 2

Traction, Saltation, Suspension, Solution

Question 3

When does Deposition occur in a River?

Answer 3

When a river loses energy, it will drop or deposit some of the material it is carrying.

Question 4

What is Hydraulic Action?

Answer 4

The force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.

Question 5

What is Abrasion?

Answer 5

Rocks carried along by the river wear down the river bed and banks.

Question 6

What is Attrition?

Answer 6

Rocks being carried by the river smash together and break into smaller, smoother and rounder particles.

Question 7

What is Solution? (Erosion)

Answer 7

Soluble particles are dissolved into the river.

Question 8

What is Solution? (Transportation)

Answer 8

Minerals are dissolved in the water and carried along in solution.

Question 9

What is Suspension?

Answer 9

Fine light material is carried along in the water.

Question 10

What is Saltation?

Answer 10

Small pebbles and stones are bounced along the river bed.

Question 11

What is Traction?

Answer 11

Large boulders and rocks are rolled along the river bed.

Question 12

Where are River Energy levels highest?

Answer 12

Energy levels are usually higher near a river’s source, when its course is steep and its valley narrow. Energy levels rise even higher in times of flood.

Question 13

Where are River Energy levels lowest?

Answer 13

Energy levels are lowest when velocity drops as a river enters a lake or sea (at the mouth).

Question 14

What is the River Channel?

Answer 14

The main part of the River that holds the water

Question 15

What factors may encourage flooding?

Answer 15

1) A Steep-Sided channel. It may cause faster surface run-off. 2) A lack of vegetation or woodland 3) A drainage basin in an urban area

Question 16

Why are Floodplains so excellent for agriculture?

Answer 16

Flooding deposits fine silt (alluvium) onto the floodplain, making it very fertile.

Question 17

What is Hard Engineering?

Answer 17

Tends to be more expensive and have a greater impact on the river and the surrounding landscape.

Question 18

What is Soft Engineering?

Answer 18

Soft options are more ecologically sensitive.

Question 19

Two examples of Hard Engineering options?

Answer 19

Dam Construction and River Engineering

Question 20

Advantages of Dams?

Answer 20

Water is held back by the dam and released in a controlled way. This controls flooding.
Water is usually stored in a reservoir behind the dam. This water can then be used to generate hydroelectric power or for recreation purposes.

Question 21

Disadvantages of Dams?

Answer 21

Building a dam can be very expensive.
Sediment is often trapped behind the wall of the dam, leading to erosion further downstream.
Settlements and agricultural land may be lost when the river valley is flooded to form a reservoir.

Question 22

What is River Engineering?

Answer 22

The river channel may be widened or deepened allowing it to carry more water. A river channel may be straightened so that water can travel faster along the course. The channel course of the river can also be altered, diverting floodwaters away from settlements.

Question 23

What is a Disadvantage of River Engineering?

Answer 23

Altering the river channel may lead to a greater risk of flooding downstream, as the water is carried there faster.

Question 24

Three examples of Soft Engineering options?

Answer 24

1) Afforestation 2) Managed flooding (also called ecological flooding) 3) Planning

Question 25

How does a meander change into an Oxbow lake?

Answer 25

Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.

Question 26

What is a confluence?

Answer 26

The point where a small river joins a larger one

Question 27

What is the watershed?

Answer 27

The boundary of the drainage baisin

Question 28

What is a tributary?

Answer 28

A stream or small river that flows into a bigger one

Question 29

Water running and falling from plants

Answer 29

Stem and drip flow

Question 30

Water running over surface of ground

Answer 30

Surface run off

Question 31

Water soaking through soil

Answer 31

Infiltration

Question 32

Water flowing through soil towards a stream

Answer 32

Through flow

Question 33

Water soaking into bedrock

Answer 33

Percolation

Question 34

Water flowing through saturated bedrock towards the river

Answer 34

Groundwater flow

Question 35

Water flowing into the river

Answer 35

Channel flow

Question 36

What does the Rising Limb show?

Answer 36

If very steep then surface run-off is very high increasing flood risk

Question 37

What does Lag-Time show?

Answer 37

If it is short then it means the river levels will rise quickly adding to the flood risk

Question 38

What does the Falling Limb show?

Answer 38

If it is gently sloping it suggests the river takes quite a long time to return to normal flow pattern. Floodrisk from another heavy rainfall

Question 39

What does Peak Discharge show?

Answer 39

This shows if a flood is likely, given the amount of water the river is able to contain.

Question 40

What is base flow?

Answer 40

Expected discharge for that time of year

Question 41

What is lag-time?

Answer 41

Time between highest rainfall and highest peak discharge.