Context: Deadly floods swept Germany and Belgium. More than 100 people have died and nearly 1,300 are missing. Many states in Germany experienced 100-150 milliliters of rainfall in just 24 hours. 

Flash floods

  • Flash floods are defined as those flood events where the rise in water is either during or within a few hours of the rainfall that produces the rise. 
  • They are highly localized events of short duration with a very high peak and usually have less than six hours between the occurrence of the rainfall and peak flood.
  • Therefore, flash floods occur within small catchments, where the response time of the drainage basin is short. 
  • Many hydrological factors have relevance to the occurrence of a flash flood: 
    • terrain gradients, 
    • soil type, 
    • vegetative cover, 
    • human habitation, 
    • antecedent rainfall
  • In steep, rocky terrain or within heavily urbanized regions, even a relatively small amount of rainfall can trigger flash flooding. 
  • These hydrological factors determine the response of the catchment to the precipitation event. Thus, a flash flood is clearly the result of the concatenation of both meteorological and hydrological circumstances.
  • Most flash floods associated with rainfall are produced by thunderstorms; that is, deep, moist convection.
  • WMO estimates that flash floods account for 85% of flooding incidents across the world, leading to around 5,000 deaths every year.

Lack of warning capabilities

  • Flash floods are highly localised with very high peaks and usually have less than six hours between the occurrence of rainfall and peak flood. 
  • There is a lack of flash flood warning capabilities across the world.

Flash Flood in India:

  • At present in India, the Central Water Commission (CWC), which monitors dams, warns of rising water levels in water reservoirs, which are usually taken to be signs of imminent floods.
  • India Meteorological Department has highly advanced capabilities with respect to computing power, Numerical Weather Prediction, vast observational network (ground, air and space based), and an internationally acclaimed Weather Forecasting System. 
  • Therefore, WMO has entrusted India with the responsibility of Regional Centre of South Asia Flash Flood Guidance System for coordination, development and its implementation.
  • Indian Meteorological Department (IMD) under the Ministry of Earth Sciences will work to customize this weather model.

Flash Flood Guidance 

  • India has launched first- of-its-kind Flash Flood Guidance services for South Asian countries — India, Bangladesh, Bhutan, Nepal and Sri Lanka.
  • It will issue impact-based forecasting of floods, which are very sudden and of short duration, at watershed and also city level.
  • The Flash Flood Guidance is a robust system designed to provide the necessary products in real-time to support the development of warnings for flash floods about 6- 12 hrs. in advance at the watershed level with resolution of 4kmx4km for the Flash Flood prone South Asian countries viz. India, Nepal, Bhutan, Bangladesh and Sri Lanka.
  • The guidance for flash floods in the form of threats (6 hours in advance) and risks (24 hours in advance) will be provided by the Regional Centre to the National Meteorological and Hydrological Services, National and State Disaster Management Authorities and all other stakeholders for taking necessary mitigation measures to reduce the loss of life and property.

World Meteorological Organization (WMO)

  • The World Meteorological Organization (WMO) is an intergovernmental organization with a membership of 193 Member States and Territories. 
  • It originated from the International Meteorological Organization (IMO), the roots of which were planted at the 1873 Vienna International Meteorological Congress.
  • WMO became the specialized agency of the United Nations for meteorology (weather and climate), operational hydrology and related geophysical sciences.'
  • WMO is headquartered in Geneva, Switzerland.