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Physical geography - hydrology and fluvial geomorphology > Flooding > Flashcards

Flooding Flashcards

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1
Q

What is fluvial flooding?

A

Occurs when excessive rainfall over an extended period of time causes a river to exceed its capacity.

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2
Q

What are the two types of fluvial flooding?

A
  • Overland flooding
  • Flash flooding
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3
Q

What is overland flooding?

A

When water levels exceed the capacity of a river channel

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4
Q

What is flash flooding?

A

Characterised by an intense, high velocity torrent of water that occurs in an existing river channel with little to no notice.

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5
Q

What is a pluvial flood?

A

A surface water flood, which is caused when heavy rainfall creates a flood event independent of an overflowing water body

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6
Q

What are two types of pluvial flooding?

A
  • Intense rain saturating an urban drainage system
  • Run-off or flowing water from rain falling on hillsides, that are unable to absorb the water.
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7
Q

Name 6 impacts of river floods

A
  • Loss of human life
  • Property damage
  • Destruction of crops
  • Possibility of waterborne diseases
  • Loss of land value in a flood plain
  • Additional costs of rehabilitation
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8
Q

How is a severity of a river flood determined? (4 ways)

A
  • Amount of precipitation in area (forecasts)
  • How long it takes for precipitation to accumulate
  • Previous saturation of local soils
  • Terrain surrounding the river
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9
Q

What is the recurrence interval?

A

Refers to the regularity of a flood of a given size

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10
Q

Name 3 ways that an area can prepare people for floods

A
  • Re-zoning of flood plains
  • Loss sharing adjustments (e.g. insurance)
  • Removal of settlements on floodplains
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11
Q

Name 3 human causes of flooding

A
  • Urban growth (impermeable surfaces)
  • Deforestation (more water available = saturated quickly)
  • Poor agricultural practices (soil exposure to elements for periods of time - dries up)
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12
Q

Name 3 physical causes of flooding

A
  • Intense rainfall (ground is saturated quickly, also areas cannot deal with large amounts of rainfall in huge amounts)
  • Impermeable rock (overland flow = increased river discharge)
  • Relief (rapid transfer of water towards rivers = chance of overflow)
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13
Q

Give 3 environmental impacts of flooding

A
  • Deposition of silt
  • Meander cut off
  • Recharged groundwater stores
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14
Q

Give 3 economic impacts of flooding

A
  • Loss of crops and farm animals
  • Overall costs/insurance
  • Infrastructure/business damage
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15
Q

Give 2 social impacts of flooding

A
  • Casualties
  • Waterborne diseases
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16
Q

What are the two types of engineering which act to prevent or ameliorate flooding?

A
  • Hard engineering
  • Soft engineering
17
Q

What is hard engineering?

A

Defence schemes that halt a rivers natural processes

18
Q

What is soft engineering?

A

Involves the use of the natural environment surrounding a river

19
Q

What is a dam?

A

A giant wall built across a rivers channel, to impede its flow.
This helps to control the discharge of the river even during prolonged rainfall

20
Q

What are the advantages of a dam?

A
  • Used to generate hydroelectric power
  • Reservoir can be used for drinking water
21
Q

What are the disadvantages of a dam?

A
  • Very expensive
  • Destroys habitats, as trapped sediment can change the chemical composition of the water
22
Q

What is straightening (hard)?

A

Blocking off meanders and constructing alternate, straighter routes.
- This moves water much faster downstream, preventing it from pooling

23
Q

What are the disadvantages of straightening?

A
  • Flooding is more likely downstream due to increased flow
  • Erosion is stronger downstream due to increased kinetic energy
24
Q

What are artificial levees?

A

Acts as embankments, extending the channels height and increasing its discharge.

25
Q

What are the advantages of artificial levees?

A
  • Resistant to erosion due to being constructed out of a strong material
  • Allows floodplains to be built on
26
Q

What are the disadvantages of artificial levees?

A
  • Increase the risk of flooding as urban development on floodplains is risky
  • If they do fail flood damage is worse than if the embankments didn’t exist.
27
Q

What is a diversion spillway?

A

Artificial channel that a river can flow into when its discharge rises
- Usually have floodgates to control the amount of water in the spillway

28
Q

What are disadvantages of a diversion spillway?

A
  • Pose a threat to areas near the confluence, increasing the risk of flooding.
  • Areas around spillway may not be used to flooding
29
Q

What is floodplain management?

A

Involves placing restrictions on land usage in the areas surrounding a river. This limits the amount of construction on the floodplain

30
Q

Give a disadvantage to floodplain zoning

A

It is hard to get rid of urban areas that are already in place on the floodplain.

31
Q

What is wetland and river bank conservation?

A

Wetland conservation involves creating conditions that are favourable for the development of wetlands (marshes or swamps)

32
Q

What are the advantages of wetland and river bank conservation?

A
  • Able to store large volumes of water which help to reduce discharge in a river
  • Create new habitats for animals, increasing biodiversity
33
Q

What are the disadvantages to wetland and river bank conservation?

A
  • The reduce the area of land available for farming
34
Q

What is river restoration?

A

Involves restoring a river that has undergone hard engineering back to its original course.
- Involves un-straightening a channel, removing artificial levees, and diversion spillways

35
Q

Give 3 advantages of river restoration

A
  • Reduces the risk of flooding further downstream
  • Allows the river to return to its course and reverse any environmental and ecological damage
  • No ongoing costs
36
Q

What are the disadvantages of river restoration?

A
  • Areas needing to be restored may be in use by people
  • Land may be valuable, down to government choices

Physical geography - hydrology and fluvial geomorphology (11 decks)

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