Flooding: Causes and Impacts

Environments at Higher Risk of Flooding

• Low-lying parts of flood plains and river estuaries Vulnerable to river flooding and groundwater flooding (after prolonged heavy rainfall)

• Low-lying areas which are partially urbanised as temporary surface water flooding common as intense rainfall has no time to infiltrate remaining soil

• Small basins are subject to flash floods (flood with v. short lag time). Usually associated w/ very intense convectional storms

Causes of Flooding

Physical Factors

Usually meteorological or longer-term climatic events

• Snow Melt/ice melt

• Rain - Heavy/prolonged/monsoonal

• Coastal storm surges Human Factors

• Channelisation

• Agriculture

  • Grazing animals trample soil
  • Ploughing compacts soil
  • Irrigation of groundwater onto arable crops

• Dams

• Impermeable areas of tarmac

• Sewers/drains

  

Flooding

Impacts of Flooding

• Environmental
  • Recharges aquifers
  • Move sediment and nutrients around the landscape into the rivers
  • Ecosystems: ↑ soil & river channel erosion = ↑ sediment and pollutants get into rivers damaging the aquatic life
  • Soils: ↓ microbial biomass in the soil
  • Eutrophication: Algal bloom on surface = ↓ O ∴ aquatic organisms die
• Socio-Economic
  • Death
  • Contamination of water supplies
  • Structural damage to properties
  • Damage to belongings
  • Crops, livestock and agriculture damaged (ruin livelihoods)
  • Harder to get flood insurance after the event (very expensive too)