The Koshi embankment near the Indo-Nepal border (at Kusaha VDC, Sunsari district, Nepal) broke on 18 August 2008.

The Kosi River's upper basin in southern Tibet and eastern Nepal drains some 60,000 km2 of mountainous terrain,[5] a region that tectonic forces are elevating by about 1 cm a year.

[6] If erosion keeps pace with geologic uplift, an estimated 600 million cubic meters of sediment would be carried downstream in an average year.

However, empirical measurements of the river's sediment load have yielded estimates of 100 million cubic meters annually,[7] indicating that the area is rising.

The Kosi alluvial fan is one of the largest in the world, covering some 15,000 km2 and extending 180 km from the outermost foothills of the Himalayas to the Ganges river valley.

Preventative flood control measures include upstream reservoirs that can also serve irrigation needs and produce hydroelectric power.

[12] Flooding occurred throughout the Kosi River valley in northern Bihar, in the districts of Supaul, Araria, Saharsa, Madhepura, Bhagalpur, Khagaria and Purnea.

Chief Minister Nitish Kumar requested a rehabilitation package of Rs 145 billion from the central government for the flood ravaged Kosi region.

[23] On 1 September, describing the floods as a "disaster," the Dalai Lama gave 1,000,000 rupees to the Bihar government for relief work.

[24] The Government of Bihar initiated Kosi Reconstruction and Rehabilitation Programme covering 30,000 affected families in Saharsa, Supaul and Madhepura district based on a pilot project implemented by ODR Collaborative, a network of organisations, supporting the Government and an owner driven reconstruction policy was formulated to support each family with Rs.

After signing an agreement with the World Bank in January 2011, this programme has been upscaled to cover 100,000 families for reconstruction of hazard safe houses.

[25] The Government of Bihar has also partnered with ODR Collaborative and UNDP to continue the social and technical facilitation and capacity building for this 'owner driven reconstruction' programme.

[27] Fax messages sent by engineers at the Kosi dam warning the state government of the impending disaster went unheeded as the official authorised to respond was on leave.