Extent of flooding in India: Rastriya Barh Agog (RBA) estimated in 1980 that India’s total flood-prone area was 40 mha, further revised to 49.815 mha.
Floods are a recurrent phenomenon, which cause huge loss of lives and damage to livelihood systems, property, infrastructure, and public utilities. Flood related damages show an increasing trend.
Causes of floods
- Natural and Meteorological factors:
- 80% of precipitation in India takes place in monsoon months from June to September. Concentrated rainfalls in a short span of time and events such as cloud bursts, glacial lake outbursts etc. often cause floods in Himalayan Rivers.
- Flooding in these areas is primarily caused by overflowing rivers. Most floods are caused by the Brahmaputra and Barak rivers in Assam, as well as its tributaries, and the Kosi River in Bihar. The flooding in these rivers is frequently exacerbated by
- Erosion and silting of the riverbeds, resulting in a reduction of the carrying capacity of river channels
- Earthquakes and landslides leading to changes in river courses and obstructions to flow
- Synchronization of floods in the main and tributary rivers
- Inflow from neighboring states
- Embankment are very old and often break down.
- Anthropogenic influences: Deforestation, drainage congestion, encroachment on natural water bodies, unsustainable river-bed mining, poorly planned construction activities, and climate change-induced extreme weather events
- Centre and state do not take a coordinated approach: Brahmaputra Board, which was established under the Brahmaputra Board Act of 1980, does not work in tandem with the state government. The Assam Disaster Management Authority and the National Disaster Management Authority exhibit similar lack of coordination (NDMA).
- Multipurpose dams' untapped potential: Dams in Assam and Bihar are primarily designed for hydropower purposes and lack storage room for flood control.
- Trans boundary management of rivers: Absence of real time sharing of hydrological data and poor coordination among river basin nations about river flow management is an issue.
- Lack of flood plain zoning: Despite Union Government circulating Model Law on Flood Plain Zoning only three states have framed laws on river zoning. Major flood prone states such as Assam and Bihar have not enacted flood plain laws. Issues such as high population density and non-availability of sufficient land for relocation people occupying flood plains need to be addressed.
- Lack of integrated reservoir operation: Reservoir operation in one state often results in floods in another state in case of inter-state rivers.
Approach to flood management Approaches to dealing with floods may be any one or a combination of the following available options:Attempts to modify the floodAttempts to modify the susceptibility to flood damageAttempts to modify the loss burdenBearing the loss.The main thrust of the flood protection program undertaken in India so far has been an attempt to modify the flood in the form of physical (structural) measures to prevent the floodwaters from reaching potential damage centers and modify susceptibility to flood damage through early warning systems.
Flood Management Measures: (Structural)The following structural measures are generally adopted for flood protection:Embankments, flood walls, sea wallsDams and reservoirsNatural detention basinsChannel improvementDrainage improvementDiversion of flood waters.Non-structural measures include:Flood forecasting and warningFloodplain zoningFlood fightingFlood proofingFlood insurance.
Flood forecasting and warning in India Of all the non-structural measures for flood management which rely on the modification of susceptibility to flood damage, the one which is gaining increased/ sustained attention of planners and acceptance by the public is flood forecasting and warning, which enable forewarning as to when the river is going to use its floodplain, to what extent and for how long. As for the strategy of laying more emphasis on non-structural measures, a nationwide flood forecasting, and warning system has been established by the Central Water Commission.
Recommendations by National Water Policy for Flood Management
- Master plan: There should be a master plan for flood control and management for each flood prone basin.
- Effectively implementing floodplain zoning regulations: States especially flood prone ones ex. Bihar, Assam etc. should be financially incentivised to enact the Model bill on Flood Plain Zoning.
- Modernisation of collection of hydro-meteorological data, flood forecast formulation and forecast dissemination. Further, simplified data dissemination policy for use of data by the States particularly regarding trans-boundary rivers to be developed.
- Focus on research to forecast flash flood with sufficient lead time will provide a much-needed relief from menace of flash floods.
- Reclamation of existing wetlands/natural depressions should be prohibited by state governments and they should formulate an action plan for using them for flood moderation.
- Projects for interlinking of rivers for diversion of flood water to water scare areas should be expedited.
- Encroachment of natural detention basins needs to be curbed and these basins should be restored to their natural state as a measure for flood control.
- Construction of large storage reservoirs which moderate flood peaks by adopting reservoir operation schedule.
- Rule curve/level for all reservoirs should be updated accounting for change in rainfall trend and change in demand due to rapid increase in population, urbanisation and industrialisation. Rule curves of major reservoirs, where flood cushion is not in-built, need to be reviewed to have some dynamic flood cushion for major part of flood season.
- Better reservoir management: Adequate flood-cushion should be provided in water storage projects, wherever feasible, to facilitate better flood management. In highly flood prone areas, flood control should be given overriding consideration in reservoir regulation policy even at the cost of sacrificing some irrigation or power benefits.
- Emphasis on Non-Structural measures: While physical flood protection works like embankments and dykes will continue to be necessary, increased emphasis should be laid on non-structural measures such as flood forecasting and warning, flood plain zoning and flood proofing for the minimisation of losses and to reduce the recurring expenditure on flood relief.
- Settlement Planning: There should be strict regulation of settlements and economic activity in the flood plain zones along with flood proofing, to minimise the loss of life and property on account of floods.
There is a need for political will, proper planning and implementation. Flood management can prove to be a viable solution for aggravating water stress in India.
Shifting the focus from mindless construction of embankments to flood mitigating policies that complement the existing embankments and accentuate the impact of floods. National Water Policy of 2012 proposes undertaking morphological studies as a basis for designing, constructing, and maintaining revetments, spurs, and embankments, among other things.
An integrated approach to managing floods is needed that works simultaneously for water management, physical planning, land use, agriculture, transport and urban development as well as nature conservation.
Ex. Wetlands, locally known as beels, act as reservoirs and rejuvenating them before monsoon can help in mitigating flood in parts.