Bihar, predominantly a landlocked state in eastern India, shares borders with Uttar Pradesh to the west, Jharkhand to the south, West Bengal to the east, and Nepal to the north. Its geographical setting plays a significant role in its vulnerability to flooding.
Rivers: Bihar is crisscrossed by numerous rivers, with the Ganges being the most prominent. Other major rivers include the Kosi, Gandak, Bagmati, and Sone. These rivers, especially the Kosi (often called the “Sorrow of Bihar”), frequently overflow their banks during monsoon seasons, contributing to large-scale flooding.
Topography: The state’s landscape is divided into two major regions:
The Northern Plains: This region lies north of the Ganges and extends up to the foothills of the Himalayas in Nepal. It is a flat alluvial plain, highly fertile but also highly flood-prone due to the rivers that flow down from the Himalayas.
The Southern Region: The region south of the Ganges consists of slightly elevated plains, including parts of the Chota Nagpur Plateau, which are less prone to floods.
Causes of Flooding in Bihar
Heavy and Intense Rainfall: Bihar receives most of its rainfall during the monsoon season (July to September). The state is hit by southwest monsoons that bring intense and concentrated downpours. Due to this, rivers in Bihar swell beyond their capacity, leading to overflowing.
Unpredictable Rainfall Patterns: Changes in monsoon patterns can result in excessive rainfall over a short period, which overwhelms the drainage systems and causes flash floods. Sometimes, rain can be heavier upstream in Nepal, affecting Bihar’s rivers downstream.
Himalayan Rivers and Snowmelt
River Systems Flowing from the Himalayas: Bihar is downstream from Nepal, and several rivers like the Kosi, Gandak, and Bagmati originate from the Himalayan region. During the monsoon, heavy rains in the Himalayas combined with the melting of glaciers increase the volume of these rivers. The steep gradient in Nepal causes rapid flow, but upon entering the flat plains of Bihar, the rivers lose speed and begin to flood.
Glacial Melting: Warmer temperatures in the Himalayas lead to faster melting of glaciers, contributing more water to the rivers that flow into Bihar, which worsens the flood risk during the monsoon.
River Siltation
Sediment Deposition: The rivers flowing from the Himalayas carry a huge amount of silt and sediment. Over time, this sediment gets deposited in the riverbeds, reducing their carrying capacity. The Kosi River is notorious for changing its course due to heavy siltation, which leads to unpredictable and destructive flooding.
Riverbed Rising: As silt builds up in the riverbed, the water level rises and even a moderate increase in water flow can lead to flooding.
Failure of Flood Control Measures
Embankment Failures: Embankments have been built along many rivers in Bihar to control floods, but they are often poorly maintained or inadequate to handle large volumes of water. During heavy monsoons, these embankments often breach, causing severe and uncontrolled flooding.
Poorly Planned Infrastructure: Dams and reservoirs meant to control river flows can sometimes worsen the problem if not managed properly. Releasing excess water from dams can lead to sudden floods downstream, which happened during several past floods in Bihar.
Deforestation and Environmental Degradation
- Deforestation in the Himalayas: In upstream areas, particularly in Nepal, deforestation increases soil erosion. This not only adds to river siltation but also reduces the ability of forests to act as a buffer, allowing more water to flow rapidly into rivers.
- Land Use Changes: Unplanned urbanization and encroachment into wetlands, floodplains, and riverbanks in Bihar have reduced the natural absorption capacity of the land. This leads to quicker runoff into rivers and exacerbates flooding.
Uncontrolled Urbanization
- Encroachment on Floodplains: Rapid and unregulated urban development in flood-prone areas has reduced natural floodplains and drainage capacity. Buildings, roads, and other infrastructure block the natural flow of water, creating artificial barriers that make urban areas more prone to flooding.
- Inadequate Drainage Systems: Urban centres in Bihar often lack proper drainage systems. During heavy rains, the water has nowhere to go, leading to waterlogging and localized flooding, particularly in cities like Patna.
International Factors
- Lack of Transboundary Water Management: Since many of Bihar’s rivers originate in Nepal, the state relies heavily on transboundary water management between the two countries. However, the lack of comprehensive flood management strategies between India and Nepal often leads to delayed responses, making flood control difficult.
- Release of Water from Nepal: During heavy rains, water released from Nepal’s dams flows into Bihar, causing rivers to overflow, especially in northern parts of the state.
Inefficient Early Warning Systems
- Lack of Timely Warnings: The flood forecasting systems in place are not always efficient. There are often delays in communication or inadequate technology to predict and warn people about floods in a timely manner. This leads to last-minute evacuations and uncoordinated disaster response.
These factors combine to make Bihar highly vulnerable to seasonal flooding, leading to repeated humanitarian crises and economic damage each year. Addressing these causes requires a multi-pronged approach that includes improved infrastructure, better water management, environmental conservation, and transboundary cooperation.
Impact on Communities
- Humanitarian Crisis: Highlight the loss of life, displacement, and the struggles of affected families. Discuss how floods damage homes, crops, and infrastructure.
- Economic Losses: Provide statistics on the economic toll, including loss of agricultural productivity, damages to property, and the cost of rebuilding efforts.
- Health Concerns: Discuss the rise in waterborne diseases such as cholera, malaria, and the challenges of accessing clean drinking water during floods.
Government and NGO Response
- Relief Measures: Detail the relief efforts by the Bihar government, national disaster management teams, and international or local NGOs. Include evacuation plans, distribution of aid, and temporary shelters.
- Criticism and Gaps: Mention any shortcomings in the relief efforts – delays in aid, insufficient infrastructure, or lack of preparedness.
- Resilience and Recovery: Focus on rehabilitation programs aimed at rebuilding homes, schools, and hospitals after the floodwaters recede.
Long-Term Solutions and Mitigation
- Flood Management Systems: Explore existing flood control infrastructure like embankments, dams, and drainage systems. Discuss the need for improvements in flood forecasting and early warning systems.
- Sustainable Practices: Suggest long-term strategies like afforestation, better water management, sustainable agriculture, and eco-friendly urban planning to mitigate future floods.
- Community Involvement: Emphasize the role of local communities and volunteers in flood preparedness, risk assessment, and implementing grassroots solutions.
Floods as a Curse
Humanitarian Crisis
oLoss of Life: Floods in Bihar often result in significant loss of life, both directly due to drowning and indirectly through waterborne diseases such as cholera, dysentery, and malaria.
oDisplacement and Homelessness: Every year, millions are displaced by the floodwaters, forcing families to abandon their homes and live in temporary shelters, which are often inadequate and unsanitary.
oDestruction of Infrastructure: Roads, bridges, schools, and hospitals are frequently destroyed, leaving communities cut off from essential services. The economic cost of rebuilding damaged infrastructure is enormous and strains local and state budgets.
Economic Impact
oAgricultural Losses: Bihar is an agrarian state, and floods damage standing crops, destroy stored grains, and erode fertile topsoil. This causes food shortages and economic hardship for farmers, who are the backbone of the state’s economy.
oLoss of Livelihoods: Beyond agriculture, floods also disrupt small businesses, labour markets, and industrial activities, leading to significant loss of livelihoods in both rural and urban areas.
oPoverty Cycle: For many people, repeated floods push them deeper into poverty, as homes, crops, and savings are wiped out year after year, with little chance of recovery.
Health and Sanitation Crisis
oWaterborne Diseases: Floodwaters contaminate drinking water sources, leading to outbreaks of diseases. Poor sanitation and lack of access to clean water exacerbate health problems.
oMalnutrition: Floods disrupt food supply chains and reduce access to nutritious food, especially in rural areas, leading to malnutrition, particularly among children.
Environmental Degradation
oSoil Erosion: The fast-flowing floodwaters erode topsoil, which reduces agricultural productivity in the long term. The deposition of silt in unwanted areas, such as roads and residential spaces, creates further issues.
oHabitat Loss: Floods can also damage forests, wetlands, and other ecosystems, causing long-term environmental damage.
Bihar Flood: Loss and Damage Observation
| Year | Districts Affected | Human Casualties | Affected Population | Houses Damaged | Crop Damage (in hectares) | Economic Loss (in INR crores) |
| 2008 | 18 | 527 | 3.3 million | 330,000 | 312,000 | 13,000 |
| 2017 | 19 | 514 | 17.2 million | 700,000 | 720,000 | 8,000 |
| 2019 | 13 | 130 | 8 million | 130,000 | 150,000 | 2,000 |
| 2020 | 16 | 27 | 8.4 million | 175,000 | 700,000 | 5,800 |
| 2021 | 15 | 215 | 7.2 million | 100,000 | 550,000 | 6,000 |
| 2023 | 14 | 40 | 5.4 million | 80,000 | 400,000 | 3,500 |
Source: Bihar State Disaster Management Authority (BSDMA), which tracks annual flood impacts.
Key Highlights from the Table
1.2008 Kosi Flood: One of the most devastating floods in Bihar’s history, caused by a breach in the Kosi River’s embankment. It displaced millions and caused catastrophic damage, with an economic loss estimated at ₹13,000 crore.
2.2017 Flood: Among the worst floods in recent years, with over 500 deaths and massive damage to crops and homes, affecting over 17 million people.
3.2020 Flood: A comparatively less deadly flood, with fewer human casualties (27), but still causing significant displacement and damage to homes and crops.
Comparative Observations
- The Kosi flood of 2008 stands out due to the breach of embankments, which made it an extraordinary event compared to regular monsoon floods.
- In terms of economic loss, the 2007 and 2017 floods were among the most damaging due to the extent of destruction in densely populated regions.
- Casualties and affected population have generally declined in more recent years due to better disaster response and early warning systems, though challenges remain in rural and flood-prone areas.
This table shows the evolving impact of floods in Bihar and highlights the need for stronger infrastructure and disaster management to reduce recurring losses.
Floods as a Blessing
Replenishment of Soil Fertility
oNutrient Deposition: Floodwaters bring fresh silt and sediments from the Himalayan rivers, which are rich in nutrients. This natural process rejuvenates the farmlands by replenishing soil fertility, especially in the northern plains of Bihar. This contributes to better yields of crops like rice, wheat, and sugarcane after the floods recede.
oTraditional Farming Benefits: For centuries, floods have been a crucial part of the agricultural cycle in Bihar. Many farmers rely on the nutrient-rich soil left behind by the floodwaters for their crops.
Recharge of Groundwater
oAquifer Replenishment: Floods help recharge the groundwater table, which is essential for agriculture and drinking water supply. In regions where water levels are depleting, the floodwaters seep into the ground, maintaining the balance of underground aquifers.
oWater Security: Given the erratic monsoon and drought patterns, floods can sometimes ensure that water is available in wells and reservoirs throughout the year.
Ecological Balance
oSupport for Wetlands: Bihar’s floodplains are home to several wetlands that provide habitat for diverse flora and fauna. Periodic flooding helps sustain these wetlands, which are essential for biodiversity and ecological balance.
oFisheries: Floods contribute to the growth of fish populations by creating new water bodies and expanding river systems. This benefits local fishing communities that depend on seasonal fish catch for their livelihoods.
While floods in Bihar undeniably cause massive destruction, displace millions of people, and contribute to economic hardship, they also play a role in maintaining the ecological balance and soil fertility that benefits agriculture in the long run. The key issue is how well-prepared the state is for these recurring floods.
[The writer is Sr. Programme Manager and National Coordinator at Society for Bright Future-New Delhi. [email protected]]