Floods in Bihar

A view of 2008 Bihar flood

Bihar is India's most flood-prone State, with 76% of the population in the north Bihar living under the recurring threat of flood devastation.^[1] According to some historical data, 16.5% of the total flood affected area in India is located in Bihar while 22.1% of the flood affected population in India lives in Bihar.^[2] About 68,800 square kilometres (26,600 sq mi) out of total geographical area of 94,160 square kilometres (36,360 sq mi) comprising 73.06% is flood affected. Floods in Bihar are a recurring disaster which on an annual basis destroys thousands of human lives apart from livestock and assets worth millions.^[1] The 2013 Flood in Bihar affected more than 5.9 million people in 3,768 villages in 20 districts of the state.^[3]

History

Recent Chronology

Recent year in which human death due to flood is more than 100.

Map of floods in India showing North Bihar as a flood-prone area

• 1984 Bihar flood
• 1986 Bihar flood
• 1987 Bihar flood
• 1993 Bihar flood
• 1995 Bihar flood
• 1996 Bihar flood
• 1997 Bihar flood
• 1998 Bihar flood
• 1999 Bihar flood
• 2001 Bihar flood
• 2002 Bihar flood
• 2003 Bihar flood
• 2004 Bihar flood
• 2007 Bihar flood
• 2008 Bihar flood
• 2013 Bihar Flood

Reason for flooding

Geographically Nepal is a mountainous region. 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. To protect the Koshi River dam as well as the Koshi Barrage Pool's embankments, Indian engineers who are in charge of the dam in Nepal, further open the dam's gates which can cause flooding down river in Bihar. In 2008 during a high flow episode a breach in the East Koshi afflux embankment above the dam occurred and the Koshi river, known for centuries as the Sorrow of Bihar, picked up an old channel it had abandoned over 100 years previously near the border with Nepal and India. Approximately 2.7 million people were affected as the river broke its embankment at Kusaha in Nepal, submerging several districts of Nepal and India. 95% of the Koshi's total flowed through the new course.

Embankments

A recent fact finding report for the Kosi floods of 2008, prepared by a civil society organization by various experts like Dr. Sudhir Sharma, Dr. Dinesh Kumar Mishra, and Dr Gopal Krishna, highlighted that although India has built over 3000 km of embankments in Bihar over the last few decades, 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.

The Fact Finding Mission recently released a report titled Kosi Deluge: The Worst is Still to Come, in which it stressed that embankments straitjacket the river. In the case of the Kosi, it found that because of siltation the river bed was in fact several feet higher than the adjoining land. The high and low lands separated by embankments have created a situation where the low lands have become permanently waterlogged. Sixteen per cent of the land mass of north Bihar is subject to permanent waterlogging.

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.

Deforestation

Deforestation in the catchment area has led to increase in the silt content of the river flow. The total catchment area of the Kosi is 74,030 km², excluding the catchment areas of its two important tributaries, the Kamla (7,232 km²) and the Bagmati (14,384 km²). These tributaries of the Kosi are important in themselves and are generally dealt with separately. Out of the total catchment of the Kosi, only 11,410 km² are located in India and the rest (62,620 km²) lie in Nepal and Tibet. The river's catchment area at Triveni in Nepal is 59,550 km². The average rainfall in the upper catchment of the Kosi is 1,589 mm while in the lower areas it is 1,323 mm. The average annual silt load of the river is 92,400 acre feet (114,000,000 m³).

Farrakha barrage

The period 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 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.

Farrakha barrage has led to following problems upstream of the barrage:

• Interception of the flow channel/ changed from straight to oblique
• Sedimentation (640 x106 metric tonnes/ year)
• Reduction of the cross-sectional area
• Declining slope of the long profile
• Widening of the river and increasing length
• Increase in flood frequency and magnitude

Affected rivers

North Bihar is a playfield of eight major rivers. All these rivers end up in Ganges.

• Ghaghra
• Gandak
• Budhi Gandak
• Bagmati
• Kamala
• Bhutahi Balan
• Kosi
• Mahananda

Statistics

See also

• CNN-IBN 30 Minutes documenetary on Bihar Floods 2008 by Marya Shakil - Part 1 Part 2 Part 3 Part 4
• 2008 Indian floods

Gallery

• 

  An old picture of 1935 flood in flood

• 

  A view of 2008 Bihar flood

• 

  The Kosi before it flooded in August 2008

• 

  The Kosi during the August 2008 flood

References