Flooding Flashcards
(36 cards)
What is fluvial flooding?
Occurs when excessive rainfall over an extended period of time causes a river to exceed its capacity.
What are the two types of fluvial flooding?
- Overland flooding
- Flash flooding
What is overland flooding?
When water levels exceed the capacity of a river channel
What is flash flooding?
Characterised by an intense, high velocity torrent of water that occurs in an existing river channel with little to no notice.
What is a pluvial flood?
A surface water flood, which is caused when heavy rainfall creates a flood event independent of an overflowing water body
What are two types of pluvial flooding?
- Intense rain saturating an urban drainage system
- Run-off or flowing water from rain falling on hillsides, that are unable to absorb the water.
Name 6 impacts of river floods
- 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
How is a severity of a river flood determined? (4 ways)
- Amount of precipitation in area (forecasts)
- How long it takes for precipitation to accumulate
- Previous saturation of local soils
- Terrain surrounding the river
What is the recurrence interval?
Refers to the regularity of a flood of a given size
Name 3 ways that an area can prepare people for floods
- Re-zoning of flood plains
- Loss sharing adjustments (e.g. insurance)
- Removal of settlements on floodplains
Name 3 human causes of flooding
- Urban growth (impermeable surfaces)
- Deforestation (more water available = saturated quickly)
- Poor agricultural practices (soil exposure to elements for periods of time - dries up)
Name 3 physical causes of flooding
- 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)
Give 3 environmental impacts of flooding
- Deposition of silt
- Meander cut off
- Recharged groundwater stores
Give 3 economic impacts of flooding
- Loss of crops and farm animals
- Overall costs/insurance
- Infrastructure/business damage
Give 2 social impacts of flooding
- Casualties
- Waterborne diseases
What are the two types of engineering which act to prevent or ameliorate flooding?
- Hard engineering
- Soft engineering
What is hard engineering?
Defence schemes that halt a rivers natural processes
What is soft engineering?
Involves the use of the natural environment surrounding a river
What is a dam?
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
What are the advantages of a dam?
- Used to generate hydroelectric power
- Reservoir can be used for drinking water
What are the disadvantages of a dam?
- Very expensive
- Destroys habitats, as trapped sediment can change the chemical composition of the water
What is straightening (hard)?
Blocking off meanders and constructing alternate, straighter routes.
- This moves water much faster downstream, preventing it from pooling
What are the disadvantages of straightening?
- Flooding is more likely downstream due to increased flow
- Erosion is stronger downstream due to increased kinetic energy
What are artificial levees?
Acts as embankments, extending the channels height and increasing its discharge.
