FLOODS

Floods are the most frequent natural calamity that India has to face almost every year in varying magnitudes in some or other parts of the country. The annual precipitation including snow-fall is estimated at 4000 Billion Cubic Metre (BCM). Out of this, the seasonal rainfall in monsoon is of the order of 3000 BCM. Rainfall in India is mainly dependent on the South-West and North-East monsoons, on cyclonic depressions and disturbances and on violent local storms. Most of the rainfall in India (80%) takes place under the influence of South-West monsoon between June and September (4 months). Remaining (20%) rainfall is received from North-east monsoon, cyclonic storm, local storms and cloud bursts. Flooding is caused by the inadequate capacity within the banks of the rivers to contain the high flows brought down from the upper catchment due to heavy rainfall. Areas having poor drainage characteristic get flooded by accumulation of water from heavy rainfall. According to the estimate of the National Commission on Flood, the area prone to floods in the country was of the order of 40 million hectares, out of which it is considered that 80%, i.e., 32 million hectares could be provided with reasonable degree of protection.