The India Meteorological Department (IMD) will soon be able to issue flash flood alerts with its ambitious “flash flood guidance FFG system”. FFG systems are specialised forecasting and early-warning systems for flash floods.
The system will forecast the impact of rainfall warning that would alert States/cities on whether a particular spell of rain could lead to flooding after assessment of soil condition, moisture level and topography of the particular area.
According to Director General of IMD KJ Ramesh, the new system will help take precautionary measures in advance in case of sudden flood in any specific area.
“Rainfall spell would flood an area often depends on interplay of factors that include the temperature, soil condition, soil depth, antecedent soil moisture conditions, state of the drainage system, topography and the amount of rain. The trial run is going on the system,” said an official of IMD.
Elaborating the FFG system, officials said that real-time data input comes from remote sensing satellite radar tracking rainfall in the region and hydrological models based on local climatic and geographic conditions.
“Flash flood guidance systems focus primarily on heavy rainfall and rainfall on saturated soils. The systems seek to identify the amount of rainfall that exceeds a water body’s carrying capacity,” official added.
For instance soil condition of Rajasthan and Madhya Pradesh can absorb 10 to 20 cm rainfall. On the other hand, soil conditions of Uttarakhand cannot absorb 10 cm or 20 cm rainfall so there are chances of flood-like situation.
“Presently the IMD issues warnings for heavy rain but these have mostly failed to prompt States into taking pre-emptive measures. What needs to be done is to convert that forecast into a flood warning. Will the rain flood the city or notIJ, an official said.
To forecast the floods, the IMD operates Flood Meteorological Offices (FMOs) at 13 locations, which include Agra, Ahmedabad, Asansol, Bhubaneswar, Guwahati, Hyderabad, Jalpaiguri, lucknow, New Delhi, Patna, Srinagar, Bangaluru and Chennai with the support of Central Water Commission.
Apart from this, the IMD also supports Damodar Valley Corporation (DVC) by providing Quantitative Precipitation Estimation (QPF) for Damodar river basin areas for their flood forecasting activities. During the flood season, FMOs provide valuable meteorological support to the Central Water Commission (CWC) for issuing flood warnings in respect of the 43 rivers of India covering 146 river basins.
CWC is working in close association with IMD and State Governments for timely flood forecast whenever the river water level rises above warning level. In a pilot mode, mathematical models for rainfall runoff estimation (like MIKE-11 FF) are used for some of the sites in Damodar Basin, Godavari Basin, Mahanadi Basin & Chambal Basin.
According to reports, between 2011 and 2014, Arunachal Pradesh suffered an average annual loss of 10 per cent of the GDP. The State has been reporting significant flood damages since early 2000s. Sikkim witnessed annual average losses of 1.7 per cent of the GDP between 2011 and 2014, followed by Meghalaya, at 1.5 per cent of the GDP during the same period. For Himachal Pradesh, annual average losses between 2011 and 2013 stood at 1.8 per cent of the GDP. Hilly regions suffer more due to flash floods which are difficult to predict and also cause landslides.