In India, floods are recurring phenomena. Almost every year some or the other parts of the country are affected by floods of varying magnitude. Different regions of the country have different climates and rainfall patterns and as such it is also experienced that while some parts are suffering under devasting floods, another part is suffereing under drought. With the increase in population and development activity, there has been tendency to occupy the flood plains, which has resulted in more serious nature of damages over the years.
The annual precipitation in India including snow – fall is estimated at 4000 Billion Cubic Meter (BCM). Out of this, the seasonal rainfall in monsoon is of the order of 3000 BCM. Most of the rainfall in India (75%) takes place under the influence of South – West monsoon between June to September (4 months). Normal annual rainfall varies from about 100 mm in Western parts of Rajasthan to over 10000 mm in North eastern part in Meghalaya.
Any area, which has at any time been subjected to flooding, is taken as flood prone area unless it has been effectively protected. Out of the total geographical area of 329 m ha., the flood prone area has been estimated as 40 m ha. by the Rashtriya Barh Ayog in its report of 1980. Of late, the Working Group on Flood Control Programme set up by the Planning Commission for the 10th Five Year Plan has estimated the flood prone areas as 45.64 m.ha., out of which an area of 16.457 m. ha. was estimated to be protected to the end of March 2004.
The rivers in India can be broadly divided into the flowing 4 regions for study of flood problem:
- Brahmaputra Region
- Ganga Region
- North West Region
- Central India & Deccan Region
These regions have specific problems, which need to be addressed considering local conditions along with general aspects. The country has to face loss of life and damage to property due to severe floods time and time again. Heavy flood damages were experienced in the country during the monsoon of 1955, 1971, 1973, 1977, 1978, 1980, 1984, 1988, 1989, 1998, 2001 & 2004. Central Water Commission has compiled the damage figures due to flood from 1953 to 2004 on the basis of which yearly average loss to life is reported to be equal to 1590 with damage to public utilities Rs. 806.78 crore. Apart from the above, there has been damages to standing crops, dwelling units, livestock, etc. There has been intangible loss as well.
Both types of schemes – structural as well as non-structural are pursued while managaing flood problem. Structural measures include reserviour construction, channel improvement, marginal embankment construction, construction of raised platforms, raising of villages, etc. Non-structural measures include flood plain zoning, flood forecasting and warning etc.
In order to mitigate the damages from floods, a nationwide flood forecasting and warning system, as a non – structural measure, has been established by the Central Water Commission which issues flood forcasts at 173 stations in the country of which 145 stations are for river stage forecast and 27 for inflow forecast.
The 62 streams covered by the above flood – forecasting network are located in the major river systems and states given in the link below:
River systems and stations