Flood is an annual feature in India. Every year about 6 million ha of land is affected by floods. High floods cause considerable damage to crops, houses, public services, loss of human and animal life, and disruption of means of transport and communication. They disturb normal life of the people of the country’s total geographical area of 329 mha, 40 mha is prone to floods, out of which 32 million ha can be provided with reasonable degree of protection.
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Areas liable to serious flood in the country are the vast northern plains and coastal tracts of large rivers. The Bihar plain, southern and northern parts of West Bengal, the Assam valley and the Cachar valley are known for frequent floods. Areas which experience occasional and less frequent floods in the country are the Kashmir valley, the Punjab plain, the plains of Uttar Pradesh the Mahanadi, the Godavari, the Krishna delta, the Kaveri delta and lower parts of the Narmada and Tapi rivers.
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Heavy rainfall, gentle slope of river valleys, heavy deposition of silt in river-beds, and deforested hills in the catchment areas are some of the well-known causes of flood. Construction of roads, railways and canals obstructs the free flow of water in some areas and cause flood. Some of the floods in coastal areas are caused by cyclonic storms.
Large rivers have great water power potential. The Himalayas in the north, the Vindhyas, the Satpura and the Aravalli in the west, the Maikala and Chhotanagpur in the east, the Meghalaya plateau and Purvanchal the northeast, and the Western and the Eastern Ghats of the Deccan plateaus offer possibility of large scale water power development.
Sixty per cent of the total river flow is concentrated in the Himalayan rivers, 16 per cent in the Central Indian rivers (the Narmada, the Tapti, the Mahanadi, etc.), and the rest in the rivers of the Deccan plateaus. Dependable power generation from the peninsular rivers required impounding of water during the monsoon months. The Himalayan Rivers do not have such problems as their flow is appreciable ever during the critical winter months.
They however, have other kind of problems, namely difficulty in construction of large storage on account of narrow valleys, high seismism of the region and vast alluvial plain has no variation in relief. The country has exploitable power potential of about 41 million kw at 60 per cent load factor from these rivers.
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The Ganga and the Brahmaputra in north and north eastern part of the country Mahanadi in Orissa, the Godavari and the Krishna in Andhra, the Narmada and the Tapi in Gujarat, and the lakes and tidal creeks in coastal states possess some of the important and useful water ways of the country. In the past they were of great importance, which suffered with the advent of rail and roads. Withdrawal of large quantities of water for irrigation resulted in dwindling flow of many rivers.
The country has a navigable water ways of about 10,600 kms—2480 kms of navigable rivers by steamers and large country boats, 3920 kms of navigable rivers by medium sized country boats, and 4200 kms of canals and back waters navigable by country boats. The most important navigable rivers are the Ganga, the Brahmaputra and the Mahanadi. The Godavari, the Krishna, the Narmada and the Tapi are navigable near their mouths only. The rivers also supply water to cities, villages and big industrial installations.