Experience has shown that loss of lives and property can be reduced significantly by giving reliable advance information about the oncoming floods. The people could be moved to safer places in an organized manner as soon as the warning is received. Cattle and valuable property could be transferred to places of safety.
Fortunately, advances in science and technology have made it possible to predict floods. Forecasting the likely future stages of, or flow of incoming flood and its sequence at selected points along the river can be very effective in reducing flood damages. Reasonably reliable flood forecasting and warning coupled with effective follow up measures constitutes the most important measure of flood management.
The Central Water Commission is the nodal agency of the Government of India for flood forecasting and they have been involved in scientific flood forecasting on most interstate rivers regularly. There are over 150 Flood Forecast Stations all over the country managed by the Central Water Commission (C.W.C.). for addition, the various State Governments have their own flood forecast stations to meet their respective particular needs.
The flood forecasts are communicated to the concerned user authorities, at administrative and engineering levels, who have to deal with flood management. On receipt of the forecasts, these agencies disseminate the warning to the officials concerned for taking steps like strengthening the flood protection measures and to those concerned with informing the public at risk, evacuating them and organizing relief measures, if necessary.
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Generally, the State Governments set up control rooms at the State and local levels, which receive the forecasts and disseminate the warnings to all concerned as also monitor the situation till the emergency passes off and situation becomes normal.
The State authorities study the situation at different locations and indicate the danger levels in respect of all rivers with which they are concerned. As some advance notice is needed and to maintain vigilance even before the danger level is reached by the river at that location, an alert is issued when the river level is one meter below the danger level, this is called the warning level. The warning and danger levels are required to be periodically reexamined and revised as necessary. The district administration has usually well laid rules and instructions about the various steps to be taken when the warning is received. Different means of communication channels and equipments are utilized to disseminate the warnings quickly.
The management of flood forecasting and warning services requires skilled and responsible personnel. The forecasting procedure involves trained hydrological and meteorological specialists while the warning and its wide dissemination are handled by the district administration.
In river systems, which extend beyond the political boundaries of India, there often comes the need to receive useful data to indicate field conditions there so that flood forecasts become useful and reliable. In yet other cases, there is a need to share such forecasts as also hydro-meteorological data on shared river systems for mutual benefit and to be cooperative. India has such cooperative arrangements, existing or under contemplation, with the neighboring nations as are mutually agreeable. Meteorological data exchange on a regional basis is also an existing practice.
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Various approaches to deal with floods are available. As each situation is different, different adjustments or combination thereof are chosen. However, these approaches fall under the following three groups:-
1. Modify the floods i.e. don fallow water to accumulate;
2. Modify the susceptibility of the people to flood damages;
3. Modify the loss burden inflicted by floods.
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Modification of floods would involve such measures as weather modification, catchment and land use modification, physical control works such as reservoirs, embankments etc. Modification of the susceptibility of the people to floods would involve steps like flood forecasting and warning, flood proofing, and floodplain management. Modifying the loss burden would involve steps like emergency evacuation, flood fighting, public health aspects as also flood insurance, and disaster relief.
Structural measures such as storage reservoirs merely for flood relief could be very uneconomical, whereas multipurpose scheme for many other benefits in addition to flood control are economically viable. However, in such cases, there .is the likely problem of clashing priorities and conflicting requirements. Similarly embankment schemes are not tin mixed blessings. Maintenance of these costly structures also involves difficulties and constraints such as inadequate provision of funds. These have led to a greater emphasis being laid on non-structural measures such as flood forecasting and flood plain management which are the basic elements of flood preparedness.