Experts fear Kosi may have changed course

The current flood zone, experts say, is in the “Dhusan channel” which the Kosi once occupied between 1921 and 1926. Before the breach last month, the Kosi was flowing down what is called the Sapt Kosi course, about 100 km west of the Dhusan channel.

“Left to its own devices, the Kosi probably wouldn’t naturally re-occupy the Sapt Kosi course,” says Neil A Wells, a geology professor at Kent State University and co-author (with University of Michigan’s John Dorr) of a 1987 seminal paper on the Kosi’s behaviour.

“If no one did anything, you would probably have Kosi flow down both the Sapt channel and the Dhusan for several months to several years. The Sapt channel will probably gradually fill in and the Dhusan channel (or more likely multiple interconnected channels) would be subject to a lot of diverse infilling, erosion, flooding, and shifting, until it established a new course,” Wells said in an email interview with The Indian Express.

“So the fix should be perfectly fine for a few years if they do it right, barring exceptional rains and floods but it won’t last forever. It will in no way be a ‘solved problem’ that people can ignore,” said Wells.

This is echoed by Professor Emeritus B Prakash of IIT Roorkee who has worked on the Kosi since late ‘70s and Rajiv Sinha of IIT Kanpur, whose latest research is focused on flood-risk mapping of the Kosi basin.

“If the current water flows are sustained for another two to three weeks, then it is very likely that the river may stay in this position leaving behind the old position,” Sinha told The Indian Express.

This dramatic course change, he said, will force geoscientists to rethink all assumptions about Kosi flooding.

The change is all the more startling given that up to the 1950s, Kosi was always shifting westward because of the terrain. But after embankments came up in the 60s, silting elevated the river bed on the eastern side.

“After rising of the river bed, we have been raising the height of embankments. This is not a solution. Repairing the river back to the route is only postponing a bigger problem,” said Prakash.

“We must start thinking in terms of managing the river rather than controlling them,” said Sinha.

The Government, too, admits the dilemma. “A comprehensive study will have to be done on this,” said U N Panjiar, Secretary, Ministry of Water Resources. He said the Centre had set up a committee of experts from Central Water Commission, Ganga Flood Control Commission, Central Water and Power Research Station, Pune; professors from IIT Roorkee and NIT, Patna, and a representative from the Bihar government.

Panjiar said that while the committee constituted by the Bihar Government would look at short-term solution to check the flood, this expert committee would look at long-term solutions, including the changing of the Kosi’s course.