Among all the disasters that occur in India, floods are the most commonly occurring natural disasters due to the irregularities of the Indian monsoon. About 75% of the annual rainfall in India is concentrated in 3-4 months of the monsoon season. As a result there is very heavy discharge from rivers during the period causing widespread floods.
Floods in India: Causes and Control
( What are the causes of flood in India ? )
-Dr. Arvind Singh
What is Flood?
Flood is a state of higher water level along a river channel or on coast leading to inundation of land that is not normally submerged. Flood, therefore, is a natural disaster which causes considerable damage to the crops, livestock and human life.
What are the Causes of Flood in India? Floods are caused by natural, ecological or anthropogenic factors either individually or as a combined result. The various causes of flood in India are as follows:
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1. Heavy precipitation: Rainfall of about 15 cm or more in a single day may be beyond the carrying capacity of the river and this causes the spilling of river over natural banks. Areas affected include the west coast of Western Ghats, Assam and sub-Himalayan West Bengal and Indo-Gangetic plains.
2. Rise in river bed: Due to large gradients, the Himalayan rivers carry a large amount of silt and sand which are ultimately deposited in the catchment area, and on the river bed. Siltation reduces the carrying capacity of the river.
3. The meandering tendency of river-flow: In the flat terrain rivers have the tendency to meander or change the course within a specific boundary. Lower reaches of Gangetic plains and Brahmaputra.
4. Cyclones: Tropical cyclones accompanied by strong winds, high tidal bores causing inundation of coastal regions. Floods due to cyclone are common in the East coast of Tamil Nadu, Andhra Pradesh, Odisha and West Bengal.
5. Silting in Delta areas: Sea tides deposit silt on the river-mouths and discharge channels leading to the steady deterioration of their discharge capacity.
6. Obstruction of free-flow of rivers: Embankments, railways, canals etc. obstruct the free flow of rivers leading to flooding.
7. Inadequate drainage arrangement: After the introduction of irrigation in some areas, the sub-soil water table rises fast unless the adequate arrangement is simultaneously made for both surface and sub-surface drainage. Punjab, Haryana and Uttar Pradesh.
8. Earthquake and Landslide: This natural disaster changes the river course and consequently cause a flood.
9. Deforestation: Deforestation causes (causes of flood in India) the acceleration of runoff and lowering of infiltration. Deforestation of hill slopes leads to greater run-off which raises the water level in rivers. The Western Ghats, Siwaliks and Chotanagpur plateau region.
10. Cloud burst: Cloud bursts lead to a high amount of rainfall within a short time leading to flash floods. Flash flood generally occurs in the Himalayan region.
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Approximately 60% of the flood damage in the country occurs from river floods, while 40% is due to heavy rainfall and cyclones. Damages by the Himalayan Rivers account for 60% of the total damage in the country. In the peninsular river basins, most of the damage is due to cyclones whereas in the Himalayan Rivers about 66% is due to floods and 34% by heavy rains. About 27% of the flood damage in the country is accounted for by Bihar, 33% by Uttar Pradesh and Uttarakhand and 15% by Punjab and Haryana.
What is Flash flood?
A sudden violent flood caused by exceptionally heavy rain in a normally dry valley in a semi-arid area, the torrential stream sometimes being laden with debris. Flash floods are often caused (causes of flood in India) by:
(i) Cloud burst / heavy downpour in the mountain areas.
(ii) Rapid melting of snow and ice in mountain areas.
(iii) Glacial lake outburst in the high Himalaya; and
(iv) Failure of landslide/debris flow dams in high and rugged mountain areas.
Which are the Flood prone regions of India?
1. The basin of the Himalayan rivers covering a part of Punjab, Haryana, Himachal Pradesh, Delhi, Rajasthan, Uttar Pradesh, Bihar and West Bengal. The Kosi and the Damodar are the main rivers causing floods.
2. The North-Western river basin covering the states of Jammu and Kashmir, parts of Punjab, Haryana, Western Uttar Pradesh and Himachal Pradesh. The Jhelum, the Sutlej, the Beas the Ravi and the Chenab are the rivers causing floods in this region.
3. The Central and Peninsular river basins covering Madhya Pradesh, Odisha, Andhra Pradesh and Maharashtra, contain the Narmada the Tapi, the Chambal and the Mahanadi. Heavy floods occur in the Godavari, the Krishna the Pennar and the Cauvery at long intervals and flood problem is generally serious.
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How to Control Floods?
Floods can be controlled by adopting the following measures:
1. Construction of embankments, flood walls and ring bunds.
2. Construction of flood control reservoirs which can temporarily hold a part of flood within the storage space provided in the reservoir so that the rate of flow below the reservoir is kept within safe limits.
3. Improvement of surface drainage.
4. The arrest of bank erosion by river training works such as spurs and revetments.
5. Reducing the rate of runoff by watershed management.
6. Improvement of the river channel.
7. Construction of raised platform to be used during times of flood emergency.
8. Afforestation of the catchment areas of the rivers.
9. The building of storage dams across those small streams, which have devastated large areas in the past.
10. Desolation of those reaches of the rivers course and drainage channels which obstruct the free flow of floodwater.
11. Straightening of the meandering river channels.
12. Establishment of proper flood warning systems.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with area of specialization in Ecology. He is a dedicated Researcher having more than four dozens of published research papers in the journals of national and international repute. His main area of research is Restoration of Mined Lands. However, he has also conducted research on the Vascular Flora of Banaras Hindu University Main Campus, Varanasi (India). Furthermore, he is also an active science writer having more than 10 dozens of published science articles in different periodicals of national repute. His email address is: 
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