5.5a

• what is the benefit of regular flooding?

  it can improve farmland as silt deposits in floodwater fertilise the land
• what are the meteorological causes of flooding?

  • intense storms
  • prolonged rainfall
  • extreme monsoon rainfall
  • snowmelt
• how does prolonged rainfall cause flooding?

  • prolonged periods of heavy rainfall can cause slow onset flooding as it causes saturated overland flow
  • this can occur when a series of low pressure systems continually move across the UK. if the time gap between different depressions is short, flooding is more likely to occur
• how can intense storms cause flooding?

  an intense storm is a fast onset event. higher levels of rainwater combined with possible storm surges from the sea can leave high levels of standing water on the land --> called flash flooding
• how can extreme monsoon rainfall cause flooding?

  • a monsoon is a seasonal change in the prevailing wind. this can bring wetter weather to some areas in subtropical regions, as the global climate changes, the seas in monsoon areas get warmer and often these seasonal rains get heavier and last longer
  • monsoon rain is often a result of La Nina events, and can caused increases direct runoff and saturated overland flow can overwhelm rivers and cause flooding
• how can snowmelt cause flooding?

  • in upland glacial areas, flooding can occur in the valleys due to the snow and ice melting, this increases overland flow
  • this might occur due to unusual high temperatures
  • it can also come from volcanic activity in glacial regions --> jokulhlaup