Annual Floods in Bihar and Measures to Mitigate

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  • In recent past flooding and the associated risks have been rising with increased frequency in India which could be attributed to a number of factors, including changes in rainfall pattern, increased frequency of extreme events, in land-use changes and development into flood-prone areas as a result of socio-economic demand.
  • Of late, it has been realized that climate changes are causing a significant impact on the hydrological system and increasing the risk and vulnerability to flooding.
  • Human lives, property, environment and socio-economic are at increasing risk due to flooding.
  • Bihar is highly vulnerable to floods on account of its geo-climatic conditions and various other attributing factors.
  • The State is the most flood-prone in the country in terms of percentage of land susceptible to flooding.


  • Current events of national and international importance.
  • General issues on Environmental Ecology, Bio-diversity and Climate Change

Mains: GS III- Disaster and disaster management.


What is the issue?
  • Bihar is India's most flood-prone state, with 76% population in the North Bihar living under the recurring threat of flood devastation.
  • Bihar makes up 16.5% of India's flood-affected area and 22.1% of India's flood-affected population.
  • About 73.06% of Bihar's geographical area, ie 68,800 square kilometres out of 94,160 square kilometres, is flood affected.
  • On an annual basis, they destroy thousands of human lives apart from livestock and assets worth millions.
  • In total, they have claimed 9,500 lives since the government started publishing figures in 1979.
  • Flood in north Bihar is recurring and devastating in nature, whereas, South Bihar flood don’t cause much destruction due to safe drainage. 
  • But in recent times, some south Bihar districts have also become vulnerable to floods from Son, Punpun and Phalgu rivers.
What are the reasons for floods in Bihar?

Natural Reasons:

  • Bihar lies in the foot of Himalayas ie, south of Nepal.
  • Bihar is mostly plain area and it serves as lowland for the Himalayan rivers like Koshi, Gandak, Budhi Gandak, Bagmati, Mahananda, Bhutahi Balan, Ghagra which flow through Nepal.
  • When heavy rains occur in the mountains of central and eastern Nepal the water flows into the major drainages of Narayani, Bagmati, and Koshi rivers.
  • As these rivers cross into India they flow into the plains and lowlands of Bihar and break their banks. 
  • These rivers and their tributaries carry high levels of discharge and sediment load, which are deposited on the plains of Bihar.
  • Kosi has been referred to as the ‘sorrow of Bihar’, meandering and depositing fertile fields with abrupt heaps of silt and tearing away big chunks of land.

Man-Made Reasons:


  • Building embankments on rivers passes for flood protection.
    • But there is increasing evidence that they have made little difference to floods which have increased in fury and last longer. 
    • An Embankment is a levee, an artificial bank raised above the immediately surrounding land to redirect or prevent flooding by a river. 
    • Embankments are built to confine the channel of a river so that it does not enter farther in flood plains causing floods
    • But since the river channel is now narrower, more silt and sedimentation is accumulated at the river bed increasing the water level. 
    • Narrow channel increases the velocity of the river, which causes floods in the low-lying areas. 
    • Embankments are not suitable for rivers which carry heavy sedimentation. 
    • The Himalayan river Kosi has one of the highest annual sedimentation load in the world, making it highly prone to flooding.
      • The river bed becomes several feet higher than the adjoining land.

  • The high and low lands separated by embankments have created a situation where the new low-lying land, known as chaur, have become permanently waterlogged.
  • 16% of the landmass of north Bihar is subject to permanent waterlogging.
  • This water-logging is due to various reasons that include spilling of silted small rivers, the encroachment of drainage channels, embankment induced water-logging and presence of saucer type depression.
  • The government of India encouraged a massive embankment programme of rivers in the early 1950s against a debate that favoured leaving the rivers to their own devices.
  • In 1954, when the Bihar flood policy was first introduced, Bihar had approximately 160 km of embankments.
  • At this time, the flood-prone area in the state was estimated to be 2.5 million hectares.
  • Upon the completion of the system of embankments, 3,465 km of embankments had been constructed and were administered by the Water Resources Department (WRD).
  • However, the amount of flood-prone land increased to 6.89 million hectares by 2004.
  • The flooding propensity has increased by 2.5 times during the same time period, not to mention that embankments failed during each major flooding event.

Farakka Barrage

  • This has caused serious interception in the dynamic equilibrium of the river hindering the natural oscillation of the river within its meandering belt.
  • The meandering belt of Ganges in Malda and Murshidabad is 10 km wide.
  • The water level of the Ganges rose about 8 m upstream of the Farakka barrage.
  • The river which flowed in a South Easterly course between Rajmahal and Farakka during the early decades of this century has now formed a mighty meander loop concentration to accommodate the additional discharge accumulated due to the barrage.
  • Due to the obstruction caused by the Barrage each year nearly 640 million tonnes of silt is accumulated in the riverbed.
  • In the last three decades, this has resulted in the accumulation of nearly 18.56 billion tonnes of silt.
  • Farakka barrage has led to following problems upstream of the barrage:
    1. Interception of the flow channel/ changed from straight to oblique
    2. Sedimentation (640 x106 metric tonnes/ year)
    3. Reduction of the cross-sectional area
    4. The declining slope of the long profile
    5. Widening of the river and increasing length
    6. Increase in flood frequency and magnitude. 

Encroachment on river embankments

  • Due to the development of embankments and dams over river courses, encroachment around river embankments has increased.
  • The lack of protection of river floodplains from damaging impacts like encroachment and diversion for ‘developmental projects’ is a tragedy that affects both the river as well as those who encroach it adversely.
  • Damage to floodplains harms the riverine ecosystem, lessens groundwater recharge capacity and poses threats of flash floods. 
  • The river suffers as it is unable to occupy and transport floodwaters downstream during high rainfall events (monsoon in particular).
  • It is unable to recharge aquifers, wet the lands along its banks or provide life-sustaining conditions to plant and animal habitats along the river margins and banks.
  • It cannot also cut and deposit soil on its banks in a natural fashion or maintain its oxbow and floodplain wetlands.
  • There is immense damage to life and property.
  • Rainfall patterns are changing due to climate change, so we are required to increase the capacity of rivers to carry the water to the Sea. Only then the floods will decrease.
  • Instead, we are decreasing the capacity of the river to carry floodwaters


  • Deforestation in the catchment area has led to an increase in the silt content of the river flow. 
  • There has been increased conversion of forests to agricultural and pastoral lands, which significantly contributes to the flood damage. 

Climate Change

  • Floods were never seen as a disaster in Bihar. It was seen as replenishment of the flood plains.
  • However, in recent years, the intensity and frequency of floods have increased significantly. 
  • Add to that climate change-induced glacial melting, that causes water levels in the Kosi basin to increase dangerously.
  • This leads to more silt, and hence, catastrophic floods and related disasters.
What are the impacts of floods in Bihar?
  1. Loss of life and property
    • People suffer an immense loss of life and property, including loss of public infrastructure like bridges, roads, schools etc., during high floods.
    • As communication links and infrastructure such as power plants, roads and bridges are damaged and disrupted, some economic activities may come to a standstill.
  2. Displacement
    • People are forced to leave their homes and normal life is disrupted.
    • Thousands of people are displaced due to floods every year.
    • People are forced to relocate along with their livestock to the other side of the embankment during monsoons.
    • It is an endless cycle where houses are built and destroyed.
  3. Poor Livelihood
    • People displaced from flood-hit areas are forced to look for other means of livelihood, having their agricultural lands destroyed. 
  4. Agriculture
    • Thousands of acres of existing arable land have become waterlogged, causing tremendous loss to crops.
    • Livestock rearing has also been impacted as excessive waterlogging leads to limited grazing land.
    • Silt has also led to a shift in traditional crops as it leaves no water retention capacity in crops.
    • The sheer amount of silt and uneven land due to the shifting of deposition of silt makes farming very difficult.
    • Irrigation is another issue as the area is battered by either too little or too much water.
  5. Poor Investment
    • Governments and corporations hesitate in investing flood-prone areas as there is always the risk of loss of lives and property.
  6. Long-term Impacts
    • Damage to infrastructure also causes long-term impacts, such as disruptions to supplies of clean water, wastewater treatment, electricity, transport, communication, education and health care.
    • Loss of livelihoods, reduction in purchasing power and loss of land value in the floodplains can leave communities economically vulnerable.
    • Floods can also traumatise victims and their families for long periods of time. The loss of loved ones has deep impacts, especially on children.
    • Displacement from one's home, loss of property and disruption to business and social affairs can cause continuing stress. 
Measures to Mitigate

Focus on Preparedness

  • Embanking rivers have been a controversial technology and was known not to have worked well in China and the USA.
  • They found it hard to maintain the embankments and any breach in them would frequently offset benefits accrued over the past many years in one go.
  • We also suffered huge losses after embanking rivers in Odisha and finally, with the Damodar.
  • We learnt the bitter lesson that when a heavily silt-laden river is embanked, the sediment gets trapped within the embankments leading to the successive rise of the riverbed necessitating raising of the embankments.
  • What can be done is better preparedness through accurate weather forecasting and implementing suitable evacuation methods. 

Strengthiening embankments

  • There is a need to strengthen the existing river embankments. 
  • There is, however, a practical limit to which the embankments can be raised and maintained. 
  • Embankments should be avoided on heavily silted rivers.
  • They should only be constructed where required. 

Need for Regulations

  • Damage to floodplains harms the riverine ecosystem, lessens groundwater recharge capacity and poses threats of flash floods.
  • Enforcement of Floodplain Zoning Regulation/Flood Hazard Zoning is a must to avert floods like done in the U.S.
  • Recent floods in Kerala (2018), Bihar, Assam remind that there is un urgent to enact a river regulation zone (RRZ).
  • In Bihar, most of the times, the decision-makers go for structural measures like construction of embankments, flood retention walls, flood levees and channel improvements, etc.
  • However, it is felt that structural measures itself are not sufficient to reduce the adverse impacts of floods in the state.
  • Hence non-structural measures like flood plain management policy, building bye-laws, and flow and silt management policy are also required.
  • It contemplates the use of flood plains judiciously.

It has also been suggested that river beds be dug to maintain the water level low. But this is a short term solution, being very expensive and unsustainable. 

International Cooperation

  • The long term solution would be to form a coalition of flood-affected countries and share expertise and technologies in flood management.
  • Many nations are implementing sustainable solutions to mitigate the impact of floods and India can benefit from them.
  • There is a need for India and Nepal to come together on this issue.
  • Both India and Nepal should work together agree on a constructive way out.


Kosi Silt Management: Case Study
  • Getting rid of the excessive silt is one of the many ways to solve the problem and villagers from a village named Piprahari have found a way: water purification by using silt-based drinking water pots.
  • Apart from pots, excessive silt is also being used to build roads, landfills, brick making, and roadside excavated fields.
  • Villagers are bracing against floods by mostly making houses from the silt.
  • The communities are also looking at ways to cultivate crops that can be grown on silt instead.
  • Even though Kosi silt is slightly deficient in nutrient value, some villagers suggest that alternate crops such as watermelon can be considered by supplementing it with compost for improving soil fertility.
  • While there is cognisance of potential solutions, the Bihar government is eager to explore and scale-up the beneficial usage of silt.
  • It had been working on pilots of products with silt and establishing usage of silt in collaboration with research institutions.
  • The state also joined hands with an initiative by the UK government, the Action on Climate Today (ACT) to create innovative methods for silt management from Kosi.
  • The top-most adaptation strategy was estimating the amount of silt deposited and managing it for commercial purposes.
  • This could address the problem of recurrent floods caused due to excessive deposition of silt.
  • A study under the joint initiative shows that the excess silt has proven utility in reclaiming lowland and waterlogged areas, which can further help mitigate floods.
  • It can also be used in low-lying agricultural fields, in road construction, brick manufacturing, new landfills and perennial horticultural/medicinal crop cultivation, thereby leading to increased production and household income.
  • The study also recommends the integration of Mahatama Gandhi National Rural Employment Guarantee Schemes with the silt management process.
  • ACT is providing policy recommendations on how to manage the de-siltation process and a comprehensive framework that can be applied to other rives of Bihar.


  • Floods not only affects the infrastructure but also the socio-economic life in the state.
  • Bihar, already an economically backward state, needs immediate and long-term measures.
  • There is a need to minimize negative consequences and ill effects of flooding by means of integrated flood management.
  • Due to rising global warming, effects of climate change through extreme weather events will be more severe in the coming years.
  • It's time we adopt sustainable development practices on the ground level to prevent catastrophic impacts of floods and other disasters. 

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