5.5A Meteorological floods

• Intense storms causing Flooding:

  • These lead to flash flooding (short-lag time)
  • The precipitation rate exceeds the infiltration rate increasing surface runoff
  • Rivers capacity is rapidly exceeded
  • Common in mountainous and semi-arid areas
• Prolonged rainfall causing flooding:

  • Can occur during monsoon conditions such as in south-east Asia 
  • In parts of India 75% of the annual rainfall occurs during the monsoon
  • In 2019 severe monsoon rainfall in India led to flooding and over 1,600 deaths
  • There was 10% more rain than the 50 year average
  • Leads to the saturation of the soil
  • This means that rainfall cannot infiltrate 
  • Increases surface run off which means the water reaches the rivers more rapidly increasing the risk of flood
  • May also occur during depression (low pressure system) conditions over the UK
• Snowmelt causing flooding:

  • Rapid snowmelt can lead to flooding
  • If the snow melts faster than the water can infiltrate then surface runoff increases
  • This may be due to soil which remains frozen
  • In March 2018 following heavy snowfall 'Beast from the east' there was significant flooding in areas of Cumbria, Lancashire and Yorkshire