Floods in Bihar

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. 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. 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. The 2013 Flood in Bihar affected more than 5.9 million people in 3,768 villages in 20 districts of the state.2017 Floods affected 19 districts of North Bihar causing death of 514 people. Around 1.71 crore people are hit by the floods. This flood was result of sudden increase in water discharge through rivers- Gandak, Burhi Gandak and Bagmati , Kamla, Kosi and Mahananda- due to heavy rain in the catchment areas of the major rivers of north Bihar in Nepal.

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.

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