In the Himalayan terrain, the Kosi river is formed by the confluence of seven smaller streams, viz. Indravati, Sun Kosi, Tama Kosi, Likhu Kosi, Dudh Kosi, Arun Kosi and Tamar Kosi at different places in China, Tibet and Nepal, before its entry into the Indian state of Bihar. The Kosi river is responsible for many floods in Bihar.
The Kosi river in north Bihar plains, eastern India presents a challenge in terms of long and recurring flood hazard. Despite a long history of flood control management in the basin for more than 5 decades, the river continues to bring a lot of misery through extensive flooding. This paper revisits the flooding problem in the Kosi river basin and presents an in-depth analysis of flood hydrology.
The recent Kosi megaflood, caused by a breach in the Kosi embankment in Nepal on August 18, 2008 and a sudden change in the course of the Kosi River, was one of the most significant and damaging flood events ever to hit Bihar. The Kosi disaster also ranks as one of the greatest disasters in India.
The Kosi afflux bundh breached in Kusaha in Nepal on 18 August 2008. This was the eighth incident of its kind and the first time did a breach occur upstream of the Kosi Barrage. The ones in 1968 and 1984 were no less disastrous but this year
The recent Kosi floods have proved once again that inadequate control measures have been responsible for the recurring disasters. Typically flood control and riverine studies focus on hydrological information, whereas a much more integrated approach that pays attention to specific morphological factors is required.
A combination of short- and long-term measures that gives importance to both structural (traditional) means and non-structural techniques is required to solve the perennial flood problem in north Bihar.
The strategy of building embankments to constrain river flow and to prevent floods in north Bihar has proven to be questionable and flawed. Reliance on a dam-and-reservoir system for that purpose only offers limited protection and even greater risks of flooding in case of damage.
