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Natural Hazards > Floods > Flashcards

Floods Flashcards

1
Q

How many people does flooding affect

A

75 million

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2
Q

How many people does flooding kill

A

20,000

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3
Q

Why do flood plains and coasts support high populations

A

Good farmland and fishing

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4
Q

What are the types of floods

A

River floods.
Coastal floods.
Surface water floods ‘flash’.

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5
Q

When do river floods occur

A

When natural or artificial banks are overtopped. Usually due to high rainfall.

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6
Q

Besides rainfall what’s other causes of river floods

A 
Snow melt.
Blockages in river channels.
Straightening of channels encourages them to flow quickly and reduces natural pools and flood pains they can spread into.
Urbanisation.
Removing levees.
Deforestation.
Machinery compacting land.
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7
Q

When do coastal floods occur

A

When the height of the seas surface is raised above the normal level or waves and tides.

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8
Q

What causes coastal floods

A

Storm surges or tsunamis.

Longer term processes like regional land subsidence and global sea level rise also contribute. Thermal expansion

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9
Q

Example of regional land subsidence

A

In Scotland after ice has melted the land rebounds.

Other land like southern England were pushed up because of the weight of ice and is now receding again.

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10
Q

When do surface water floods ‘flash floods’ occur

A

Occur when heavy rainfall overwhelms the drainage capacity of the local area

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11
Q

What is the hardest flood to predict

A

Flash flood

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12
Q

What are the immediate hazards of a flood

A

Drowning or being hit by floating objects.
Electrocution.
Hypothermia.
Mudflows and debris flows.

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13
Q

What classifies a debris flow

A

47% debris in water

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14
Q

Why shouldn’t you walk or drive through flood water

A

Because 15cm of fast flowing water can knock you over.

60cm can float your car.

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15
Q

What are the long term hazards of flooding

A

Contamination of freshwater.
Epidemics of waterborne diseases.
Agricultural losses -> food shortages.
Damage to homes, schools and workplaces -> economic loss.

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16
Q

How are food shortages after a flood mitigated

A

By global distribution of food and humanitarian aid but in the past it could cause famines

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17
Q

Steps to reduce vulnerability

A 
Land use planning.
Flood reduction measures.
Flood diversion/defence measures.
Flood proofing buildings and contents.
Forecasting and warning.
Education.
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18
Q

How does landuse planning help

A

Mapping a flood hazard shows flood frequency, water depth and flow velocity.
Implement land use policies like exclusion zones and building regulations.

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19
Q

Examples of flood reduction measures

A

Reforestation to reduce sediment loss and increase uptake of water by plant roots.
Creation/protection of water retaining ecosystems like wetlands.
Permeable surfaces in urban areas.

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20
Q

Examples of flood diversion/defence measures

A 
Construct levees (artificial embankments and dykes)
Enlarge channels or create overspill channels.
Construct storage reservoirs. (Favoured)
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21
Q

Example of enlarging a channel

A

Dredge sediment

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22
Q

How to flood proof buildings

A

Elevate living space on stilts or mounds.
Sealable doors, windows and cellars.
Store food in watertight containers high up.
Electrical connections at head height.

23
Q

Example of flood proofing

A

After hurricane Hugo’s 6m flood surged caused serious damage in 1989 the rebuilt houses in S Carolina are elevated

24
Q

Down side of elevating houses

A

Accessibility issues.
Foundations and soft storey have to be really strong.
False sense of security so people could end up stranded.
Expensive.

25
Q

Example of an agency that does forecasting and warnings

A

Environmental Agency in England and Wales

26
Q

How many properties are at risk in England and Wales

A

1 in 6

27
Q

What do the environmental agency do

A

Model flood behaviour and drainage basin characteristics.
Monitor storms and predict precipitation and flood using satellite and radar data.
Issue flood alerts and warnings.

28
Q

Why can you be indirectly affected by flooding

A

Through power cuts if the infrastructure is poorly designed around town

29
Q

How do the environmental agency issue flood alters and warnings

A

Via website, local radio, email/phone/text, and in some areas sirens and loud hailers

30
Q

What are the stages of the flood altering system

A

Flood Alert
Flood warning
Severe flood warning

31
Q

What does the flood altert mean

A

Means that flooding is possible and that you need to be prepared

32
Q

What does the flooding warning mean

A

Means flooding is expected and you should take immediate action

33
Q

What does severe flood warning mean

A

Means that there is severe flooding and danger to life

34
Q

How should you respond to a flood alert

A

Tune in to local radio on battery or wind up radio.
Move items to safety.
Assemble emergency kit.
If time, fit flood protection products.

35
Q

What is in an emergency kit

A

Medication, water, spare clothes, torch.

36
Q

Examples of flood protection products

A

Flood boards
Airbrick covers
Sandbags
Toilet bungs

37
Q

What should you do if a flood warning is issued

A

Same as flood alert plus switch off electricity, gas and water supplies. Be prepared to evacuate to higher ground, call 999 if in danger

38
Q

Case study for flooding

A

Bangladesh

39
Q

What is Bangladesh classed as

A

The worlds most flood prone country

40
Q

What is the size and population of Bangladesh

A

Similar size to England and Wales but a population of 160 million

41
Q

Why is flooding a big risk in Bangladesh

A

Most people live on low lyingflood plains and rely on agriculture for their livelihood.
Largest river delta in the world.
River erosion is a problem.
Rivers swelled by snow melt in spring and monsoons in summer.

42
Q

What is the river delta in Bangladesh

A

Ganges draining an area 11x Bangladesh before it goes into Bay of Bengal

43
Q

Where does the snow melt in spring in Bangladesh comes from

A

The Himalayas

44
Q

Normally how much of Bangladesh is inundated during monsoon season

A

20-25%

45
Q

How much of Bangladesh is inundated during monsoon season during extreme events (monsoon and snow melt)

A

Up to 75% can flood

46
Q

What percentage of the population in Bangladesh life within 1m of sea level (not from the sea)

A

17%

47
Q

Why is there a threat of permanent flooding in Bangladesh

A

Sea level rise

48
Q

How many cyclones per year are in the Bay of Bengal (don’t all affect Bangladesh)

A

16

49
Q

What is a big problem in some areas of Bangladesh

A

Saline intrusion

50
Q

Why is there increasing hazard levels in Bangladesh due to climate change

A

It is subsiding and sea levels are rising.
Himilayan glaciers are melting and receding.
Long term reducing in ice cover.

51
Q

What is the organisation to reduce vulnerability in Bangladesh

A

Cyclone Preparedness Programme (CPP). Organised by the Bangladesh government and red crescent society

52
Q

What has Bangladesh done to reduce vulnerability

A

Thousands of cyclone shelters constructed and a large network of volunteers trained to disseminate warnings and assist with evacuation (no high ground so elevated).
Education and training.

53
Q

What does the N. Indian Ocean now have

A

Storm surge modelling and forecasting programme (and IOTWS) after 2004 Boxing Day tsunami

54
Q

What is the comparison between major cyclones in Bangladesh

A

In 1970 Bhola cyclone nobody knew was coming so Cyclone preparedness programme put in place. In 1991 there was some success but not enough so in 2007 the Sidr cyclone had an increased focus on training volunteers to get people to sheltered and deaths dropped dramatically with the same amount of people evacuated as in 1991.

Natural Hazards (7 decks)

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