General Flood Management Measures Practiced in India
Based on the nature work, the flood protection and flood management measures may be broadly categorized as engineering/structural measures and administrative/non-structural measures.
Engineering or Structural Measures
These engineering measures that bring relief to the flood prone areas by reducing flood flows and thereby the flood levels are: creation of artificial reservoirs behind dams across rivers; a natural depression suitably improved and regulated; diversion of a part of the peak flow to another river or basin without any damages from the diversion; and construction of parallel channels.
The engineering methods of flood protection that do not reduce the flood flow but reduce spilling are: construction of embankments; and channel and drainage improvement.
Reservoirs
Reservoirs can reduce the intensity and timing of the incoming flood. Their effectiveness depends on the available reservoir capacity. Reservoirs are more effective for flood management if specific flood space is earmarked, as in the case of Damodar Valley Corporation dams across the Damodar and its tributaries. To improve the efficiency of the reservoirs, arrangement for inflow forecasts should be made.
Detention basins
They are formed by improving the capacity of natural depressions/ swamps and lakes. The Ghaggar detention basin in Rajasthan is a good example. This method is relatively inexpensive as the land under marshes may hardly require much compensation.
Embankments
Embankments confine the flood flows and prevent spilling, thereby reduce the damage. These are cheap and quick method of flood protection. Erosion along the embankments and natural banks of the river systems has been a serious problem. The embankment shave to be suitably protected by spurs, pitching and other suitable anti-erosion measures. This method of flood management should be undertaken only after carrying out necessary hydrological and other studies regarding their favourable and adverse effects.
Channelization of rivers
While channelizing rivers, it must be keep in mind to give the river certain freedom to flow and right of way to pass its flood waters and silt load within its natural waterway.
Channel improvement
It involves improving the hydraulic conditions of the river channels by desilting, dredging, lining etc. But this method is associated with high costs and other problems. This method is economically justifiable if the channel is used for navigation purpose.
Drainage improvement
Inadequacy of natural or artificial drainage channels for carrying the storm water discharge in a reasonable time causes damage. Therefore, it is essential to improve drainage conditions by construction of new channels or improvement in the discharge capacity of the existing drainage system.
Diversion of flood waters
This method can be used in case of unusual floods around cities. Important projects under construction or under planning are the supplementary drain in Delhi, the Thottapally Spillway diversion in Kerala, the Kolleru lake diversion into the sea in Andhra Pradesh, etc.
Watershed Management
It include measures for developing and conserving the vegetative and soil covers and also construction of structural works like check-dams, detention basins, diversion channels, etc.
Administrative or Non-structural measures
The administrative methods focus on mitigation of flood damages by:facilitating timely evacuation of people to safer areas through advance warning of incoming flood; and discouraging creation of valuable assets/settlement in frequent flood prone areas. However, providing absolute protection all flood prone areas is practically impossible and economically unviable.
Flood Plain Zoning
Under this concept, it is recognised that the flood plain of a river is essentially its domain and any intrusion of developmental activities into it must recognise the river’s right of way. Flood-plain zoning involves demarcation of areas likely to be affected by floods of different magnitudes and frequencies. State governments are encouraged to implement the flood plain zoning approach.
Flood Proofing
Flood proofing measures involve raising villages above the pre-determined floods levels.
CWC National Flood Forecasting Network
The duty of flood forecasting and warning in India is entrusted with the Central Water Commission (CWC). Currently there are more than 850 Hydrological and Hydro-meteorological sites being operated by CWC across the country covering 20 river basins for observing the discharge, sediment & water quality. The flood forecasting comprises level forecasting and inflow forecasting. Level forecasting helps for evacuation of people to safer areas. The inflow forecasting is used by dam authorities for operation of reservoirs for safe passage of flow downstream.
