Embankments

A recent fact-finding report on the Kosi floods of 2008 – prepared by a civilian organization, the Fact Finding Mission on the Kosi, composed of various experts such as Sudhirendar Sharma, Dinesh Kumar Mishra, and Gopal Krishna – highlighted the fact that although India has built over 3000 km of embankments in Bihar over the last few decades, the propensity for flooding has increased by 2.5 times during the same time period, not to mention that embankments failed during each major flooding event.^[19]

The report, titled Kosi Deluge: The Worst is Still to Come, stressed that embankments straitjacket the river. In the case of the Kosi, it found that because of siltation the river bed had risen several feet in relation to the adjoining land. The high and low lands separated by embankments have created a situation where the lowlands have become permanently waterlogged. Sixteen per cent of the land mass of north Bihar is permanently waterlogged.^[19]

In 1954, when Bihar's flood policy was introduced, Bihar had approximately 160 km of embankments. At that time, the flood-prone area in the state was estimated to be 2.5 million hectares. Upon completion of the system of embankments, 3,465 km had been constructed and were administered by the Water Resources Department (WRD). However, the amount of flood-prone land had increased to 6.89 million hectares by 2004.

Farakka Barrage

The recent period has seen serious interruption in the dynamic equilibrium of the river, hindering the natural oscillation of the river within its meandering belt. The meandering belt of the Ganges in Malda and Murshidabad districts is 10 km wide. Upstream of the Farakka Barrage, the water level of the Ganges has risen about 8 meters. The river, which flowed in a South Easterly course between Rajmahal and Farakka during early decades of this century, has now formed a concentration of meander loops to accommodate the additional discharge due to the barrage. Due to the obstruction caused by the Barrage, each year nearly 640 million tonnes of silt are accumulated in the riverbed.^[20] 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:

• Interception of the flow channel being changed from straight to oblique
• Sedimentation (640 x106 metric tonnes per 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

A 2016 Central Water Commission (CWC) report on Bihar floods states that the Farakka Barrage, even under the worst scenario, can impact areas up to 42 km upstream, due to a backwater effect.^[21] Patna is located about 400 km upstream. The report blamed the number of banana plantations on the river bank between Patna and Bhagalpur as one of the reasons for the floods, based on the assessment of 100 years of flooding of the Ganga. The CWC report stated that the sedimentation in Ganga, in Bihar, is basically due to huge sediment load contributed from its northern tributaries – the Ghaghra, Gandak and Kosi rivers. The flood-affected area in Bihar was 2.5 million hectares in 1954 when the length of all embankments in Bihar was 160 km, but the flood-affected area increased to 7.295 million hectares in 2016, after the construction of 3731 km of embankments.^[22]

Contributing water sources

North Bihar is within the flood plains of eight major rivers, all of which are tributaries of the Ganges.

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