Experts fear Kosi may have changed course

The implications are crucial to deciding on the relief and reconstruction strategy. For, if this is the new course, nudging the river back to its original channel to the west, as is being planned now, could only be “postponing the problem.”

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.

“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.

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