5.5c Storm Desmond

• Date

  5th December 2015
• What caused the heavy rainfall and floods

  • very low air pressure (946 millibars) and fronts brought prolonged heavy rainfall
  • antecedent conditions -> saturated soil from previous storms and rainfall = flashy basin response, less infiltration, more run-off (with sediment, reduces capacity)
• How much rainfall fell in Cumbria

  over 1 month's worth of rainfall in one day
• Environmental impacts

  • significant soil erosion and riverbank erosion (adding to future flood risk)
  • water flooded up to 3ft
  • saturated soil led to decomposition of dead plants and animals -> release noxious gases.
• Socio-economic impacts

  • 6400 homes flooded in Cumbria
  • 60,000 power outages
  • £1.3 billion economic damage
  • £6 billion in flood insurance claims in 2015 across UK (other storms included)
  • 131 bridges in Cumbria needed inspection and repairs
  • businesses leaving area due to flood-risk -> negative multiplier effect and spiral of decline
• Mismanagement of flood defenses

  2009 Cumbrian floods led to raising riverbanks, introducing pumping stations and diversion channels. Based on a flood return period

  Flood was considered a 1 in 50 years flood but it returned 6 years later with Storm Desmond -> settlement was unprepared and water exceeded defenses