'Repeat of Kosi catastrophe soon'

Experts Of Opinion River’s Embankments Are Well Past Use-By Date

Amit Bhattacharya TNN

New Delhi: The breach in the Kosi embankment needs to be urgently plugged to bring back normalcy in Bihar, but geologists who have studied the river say the embankments will not hold for long.
‘‘These embankments aren’t going to last. I would be surprised if they hold for another 10 years. We are going to be faced with another catastrophe in the near future if other measures aren’t taken now,’’ says geologist Rajiv Sinha of IIT Kanpur.
The reason for the experts’ fear is simple. The Kosi embankments have far outlasted their ‘use-by’ date. These were built between 1956 and 1960 with a projected life of 20-25 years. While regular repairs have been reportedly done, siltation has been raising the riverbed. ‘‘It’s just a matter of time before the river breaks through again,’’ says Sinha.
The embankments were built at a time when planners believed rivers could be ‘‘controlled’’.
Says geologist S C Tandon, the pro vice-chancellor of Delhi University, ‘‘Rivers can no longer be looked at as problems of engineering. The world is moving towards integrated management of rivers. This requires studying the various factors determining the stream flow of a river and generating models to zero in on pressure points. Then solutions can be arrived at.’’
These experts say integrated management is the best bet to avoid a repeat of this year’s destruction. ‘‘The time to act is now. Before the next monsoon, we must begin to know what the river is doing,’’ says Sinha, who has a PhD from Cambridge on sedimentology in the Kosi plains.
Embankments have been preferred in India because these constructions leave scope for kickbacks to politicians and bureaucrats. But that’s just one aspect of river management, says Sinha. What’s really needed is a geomorphological study of the area —which means studying the land forms and the processes that shape them. ‘‘For this, we need to reconstruct the river patterns in the last 100 years. We need to survey the area, look at satellite and aerial imagery to learn about topographical changes taking place. We need data on water discharge and sediment load,’’ says Sinha.
These data can be used for computer simulation of the Kosi flow and ultimately lead to a predictive model for the river. ‘‘The idea is to map out the problem areas. These may not lie at the site of the breach but be upstream,’’ says Sinha.
Tandon compares a river breach to a tear in a shirt. ‘‘If a shirt tears from a particular spot, you sew it from there. But to prevent another tear, you must also look at where the pressure is coming from — maybe the stitch needs to be loosened from a particular place. It’s the same with rivers. Unless the flow and topographical features are known, it’s difficult to ascertain why a breach occurred and what could prevent it.’’
Sinha is sceptical about the efficacy of a big dam on Kosi for preventing floods. ‘‘Big dams aren’t the best solution for controlling floods. One needs to look at longterm data to see whether a dam will work.’’
Sinha, Tandon and other geologists like Vikrant Jain, a reader in DU’s department of geology, have sought a grant from the department of science and technology for urgently studying the Kosi river. ‘‘For long, crucial hydrological and sediment load data hasn’t been made available to us by the government, ostensibly because the river comes from another country, Nepal,’’ says Sinha. ‘‘But this mindset needs to change. Scientists can provide more insights into river-water sharing issues than anybody else.’’
Tandon says there’s another compelling reason why rivers like Kosi need to be scientifically studied — climate change.

Course change permanent?

Has the course of the Kosi permanently changed? Rajiv Sinha, a geologist at IIT Kanpur who has researched on the river, says it too early to answer that question. ‘‘Plugging the embankment will lead Kosi to flow on its old bed. But whether it will stay on that course will depend on how much silt has formed on it,’’ he says. Embankments don’t offer a permanent solution. Sinha says jacketing of the river can be dangerous since Kosi carries around 80 million tonnes of silt every year. ‘‘Through the breach, the river has found its lowest possible terrain. If the elevation difference between the current flood plain and Kosi’s old course is large, that is, if the old course is much higher, then it will be very difficult to bring the river back to its bed,’’ he says.