1.4 The human impact

Question 1

What is deforestation?

Answer 1

The total deliberate removal of trees by cutting down/burning them at rates faster than the natural regeneration.

Question 2

What is afforestation?

Answer 2

Planting trees in areas which previously had no forests.

Question 3

What are check dams?

Answer 3

Small dams, often in small valleys, that reduce the speed of runoff and prevent erosion.

Question 4

What is canalisation?

Answer 4

When rivers are straightened and deepened in order to make them easier to navigate by barges.

Question 5

What is cloud-seeding?

Answer 5

The dropping of crystals into clouds to cause rain.

Question 6

What is irrigation?

Answer 6

Providing water for crops by artificial means.

Question 7

Give an example of where an extended period of precipitation has caused flooding

Answer 7

Somerset levels 2014

Question 8

Give an example of where intense precipitation has caused flooding

Answer 8

Pakistan floods 2010 - due to monsoon. Particularly bad as soil was baked dry, so the hard soil reduced infiltration capacity = more surface run off

Question 9

Explain how climatic hazards cause flooding

Answer 9

e. g. cyclones, hurricanes or a low pressure system, which bring abnormally large amounts of precipitation.
e. g. Bangladesh flood 2004

Question 10

Give an example of where drainage basin characteristics (soil, geology and relief) has caused flooding

Answer 10

Boscastle 2004

Question 11

Give an example of where urbanisation has caused flooding

Answer 11

York floods 2015

Question 12

Give an example of where human river management has caused flooding

Answer 12

Mississippi floods 1993

Question 13

What is a recurrence interval?

Answer 13

How often, on average, that size of flood is likely to occur. Based on historic evidence

Question 14

How can people predict flood risk?

Answer 14

Flood risk assessment - uses historic data from past floods, present water levels are continually monitored. Focusses on source of flood, paths the water takes during flood, impact on people, land and property.

Question 15

What are dams and what do they do?

Answer 15

They are a barrier across a river with a man-made lake behind it. They regulate river flow and reduce the risk of flooding

Question 16

What are the advantages of dams?

Answer 16

At high rainfall, water can be stored in the reservoir, then released slowly during low-flow conditions

Question 17

What are the disadvantages of dams?

Answer 17

1) Controversial
2) expensive
3) reservoirs behind often flood large areas of useful land

Question 18

What is channel straightening and how does it work?

Answer 18

Artificially straightens river so water flows faster and is transferred downstream more rapidly. Increases gradient which increases velocity.
Removes meanders in rivers

Question 19

What are the advantages of channel straightening?

Answer 19

Relieves flood risk by improving rate of flow

Benefits transportation

Question 20

What are the disadvantages of channel straightening?

Answer 20

Can increase flood risk downstream (so problem shifts rather than goes away)
Concrete channelisation can create unnatural looking river environments, and can damage local wetlands and wildlife habitats

Question 21

What are river embankments and how do they work?

Answer 21

It is when the height of the river banks are raised, which increases capacity of a river channel, allowing it to hold more water before flooding occurs

Question 22

What are the advantages of river embankments?

Answer 22

Cheap and easy
Sustainable
Minimal impact on environment
Can be landscaped to provide green spaces and cycle ways

Question 23

What are the disadvantages of river embankments?

Answer 23

Concrete structures, while more effective, are expensive and ugly

Question 24

What are diversion spillways and how do they work?

Answer 24

They are artificial channels that a river can flow into when its discharge rises. Channels move water around an area at risk of flooding and send it back into river downstream or into another river.

Question 25

What are the advantages of diversion spillways?

Answer 25

Moves water around area of flooding, reducing its effects

Question 26

What are the disadvantages of diversion spillways?

Answer 26

Pose threat to areas near confluence between spillway and whichever river it flows to, as discharge here will be increased.
Path that spillways take can take water around areas not usually used to flooding. If spillway failed, this would cause widespread damage