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Environmental Risks and Hazards > L3 - Floods > Flashcards

L3 - Floods Flashcards

1
Q

What is a drainage basin?

A

Total area that contributes water to a stream

- Basic geomorphic unit

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2
Q

What is an interfluve?

A

Dividing line between drainage basins

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3
Q

Name 3 main types of causes of river floods

A
  • Atmospheric
  • Tectonic (Landslides)
  • Technologic (Dam failure)
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4
Q

Name 3 types of atmospheric causes of river floods

A
  • Rainfall
  • Snowmelt
  • Ice Jam
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5
Q

Name 2 main types of causes of coastal floods

A
  • Atmospheric (Storm surges)

- Tectonic (Tsunamis)

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6
Q

What factors increase surface runoff?

A
  • Impermeable surfaces
    e. g. urbanisation
  • Less interception
    e. g. deforestion
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7
Q

What effect might urbanisation have on a hydrograph?

A
  • A higher peak flow, representing more concentrated and immediate discharge of water
    = Higher flooding magnitude
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8
Q

What is a storm surge?

A

Difference between predicted and observed height of tide

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9
Q

What causes storm surges?

A
  • Low pressure systems

- High winds

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10
Q

How high are storm surges in Eastern England

A

2m or higher

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11
Q

What effects the location and severity of storm surges?

A
  • Coriolis effect

- Morphology of water basin e.g. English channel is shallow

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12
Q

When was a notable coastal flood due to storm surge that effected Eastern England

A

31st January 1953

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13
Q

What caused the 1953 flood?

A
  • High Spring tide
  • Low pressure system
  • Force 10-11 winds from north
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14
Q

What were the effects of the 1953 flood?

A
  • 637km land flooded (UK)
  • 307 deaths (UK)
  • 1800 deaths (NDL)
  • 24,000 homes destroyed (UK)
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15
Q

What was built in response to the 1953 flood?

A

Thames Flood Barrier in 1982

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16
Q

What return period was the Thames Flood Barrier designed to protect against

A

1 in 1000 years

- Increasingly used (sea level rise?)

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17
Q

What is the ‘underspill position’ in the Thames Flood Barrier

A

Allows controlled amount of water to pass through the barrier

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18
Q

What does the TFB protect against?

A
  • Storm surges
  • High tides
  • River flooding
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19
Q

According to the Env. Agency, what are the 5 main types of English floods?

A
  • River
  • Coastal
  • Surface water
  • Sewer
  • Groundwater - When water table rises above sea level
20
Q

What are 2 types of flood distinctive to Bangladesh?

A
  • Tidal

- Flash floods

21
Q

What are 3 typical characteristics of flood-prone envrionments

A
  • Low-lying Floodplains
  • Low-lying coastlines
  • Small, steep basins (flash floods)
  • Below unsafe dams
22
Q

Give an example of a flood of a low-lying floodplain

A

1993, Mississippi

23
Q

Give an example of a flood-prone low-lying delta

A

Song Hong delta, Vietnam

24
Q

What caused the 2007 England floods?

A
  • Jet Stream unusually far south, series of low pressure systems
  • Wet Winter follow06-07 Dec-Feb
  • Wet 07 Summer
  • Reduced evaporation
25
Q

What were the effects of the 2007 England floods?

A

Total Insured loses - £2.3-3.3 losses
Local flash floods to widespread river basin floods
Excess of 100-year rivers flows
Esp. Flooding of the Severn and the Humber

26
Q

How much rainfall was there in Pershore?

A

140+mm

27
Q

How much rain was there in Uckfield, East Sussex in the 2000 floods?

A

> 150mm in 12 hours

28
Q

What contributed to the Dec 2013 River Mole floods?

A
  • Weald Clay contributed

- Very low pressure system

29
Q

Accord to the Env. Agency 2009 report, what areas of England are more at risk of flooding?

A
  • Vale of York
  • The Wash
  • South-east coastline
  • Somerset Levels
    5. 2 million properties (1 in 6) at risk
30
Q

According to 2009 Env Agency report, what could lead flooding to get more likely?

A
  • More freq. and severe weather
  • Defences deterioration
  • Urbanisation
  • Deforestation
  • Soil degradation
31
Q

According to 2009 Env Agency report, what could lead flooding to get less likely?

A
  • Better defences
  • Less development on flood-prone areas
  • Diversion of flood water
  • Better land management
32
Q

According to 2009 Env Agency report, what could lead flood impacts to get worse?

A
  • Climate Change -> More severe events
  • Higher value of property and goods
  • Loss of insurance cover
  • New development in flood-prone areas
33
Q

According to 2009 Env Agency report, what could lead flood impacts to get better?

A
  • Better forecasting
  • Better property-level protection
  • Better response & preparedness
  • Help with recovery
34
Q

According to 2009 Env Agency report, what utility is at greatest risk?

A

Water pumping plants? - 55%

35
Q

According to 2009 Env Agency report, which region has the most people living on a floodplain?

A

Greater London - most risk of flooding

36
Q

What defines an area as being on ‘low risk’?

A

> 0.5% - 1 in 200yr

37
Q

What defines an area as being on ‘medium risk’?

A

0.5-1.3%

38
Q

What defines an area as being on ‘high risk’?

A

> 1.3% - 1 in 75yr

39
Q

What Chinese rivers flooded in 1931?

A

Yellow, Yangtze, Huai

40
Q

What caused the 1931 Chinese floods?

A
  • Heavy snowfall - Winter 1930

- Very wet spring-Aug

41
Q

How many people died 1931 Chinese floods?

A

3.7-4 million

42
Q

What did the 1931 Chinese floods prompt?

A

Three Gorges Dam

  • 181m high, 2335m long
  • $26 billion
  • 660km reservoir, 39km3
43
Q

Name two mitigation measures against flooding

A
  • Insurence (>developed)

- Disaster Aid (

44
Q

Name two protection measures against flooding

A
  • Flood abadement

- Flood control

45
Q

Name three adaptation measures against flooding

A
  • Land-use planning
  • Preparedness
  • Forecasting

Environmental Risks and Hazards (18 decks)

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