Kosi repair starts, but Nepal holds key to long-term solution

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New Delhi, Sep 2: As Bihar grapples with the worse flood in its history, caused by the marauding Kosi river, work has started to repair the breach and ensure the river flows through its original path.

When the swollen Kosi river burst its banks in a part of Nepal just north of the border with India, it changed course, now flowing through a fresh channel some 120 km to the east, it has no levees or protective embankments. The worst hit districts were Araria, Madhepura, Supaul and Purnea.

The Kosi barrage built in 1964 was meant to hold 9.3 lakh cusecs of water so that the plains of Bihar and not flooded.

Two afflux bund or channels were created on the either side to reduce the pressure on the barrage and provide irrigation to the region. On the western side the afflux bund, made of compact mud, is 12-km-long while on the eastern side the bund is 32 km long.

The bunds are periodically maintained by the government of Bihar to ensure their strength and to withhold a Kosi in spate. This year, however, no such repairs were done. Due to heavy silt deposit (see chart) the Kosi had a tendency to move eastwards. The yearly repairs ensured that the bunds were able to hold the water of the river in its normal course.

This year the bunds gave away and 1.3 km breach in the eastern afflux bund and 80% of the river water rushed through the breach while 20% of the river continued its normal route.

Now a team of experts, comprising from the centre and the state have chalked out a plan to get the river back on course.

The idea is to go upstream from the breach side and divert the water away from the afflux bund. This would allow the bund to be repaired and ensure normal course of the river.

To divert the river water from the bund, the method will be a choice between concrete porcupine, wire crating or nylon crating.

“Depending on the flow and depth of water either one of these techniques will be used. If the depth and flow is less, then wire crating or nylon crating will be used. If the flow and depth is high then concrete porcupine would be used,” said central water commission chairman A K Bajaj.

Porcupine is a revolutionary and versatile concrete block retaining wall system. It needs no mortar and requires the minimum of plant and machinery for installation. The individual Porcupine element is an interlocking curved concrete block, which achieves its stability by the grooves on the top surface of one block matching the splines on the bottom of another.

The flow of water over the past few days have reduced. From 1.7 lakh cusecs of water on Saturday the amount of water discharged was 1.2 lakh cusecs on Monday. “Work has started on the diverting the water by government of Bihar and CWC is providing the technical help,” Bajaj said.

Weather permitting, Bajaj said the work on getting the river back on course and repairing the breach does not have to wait till November. “Work has already started and we have ensured the breach doest not increase any more. One does not have to wait till the end of the monsoon period to mend the breach.”

This, however, is not the long-term solution. Bajaj stressed that in future it is imperative to construct the Kosi High Dam.

“The Kosi High Dam is the only long term and feasible solution,” Bajaj said.

For Kosi High Dam to become a reality, the government of India will have to negotiate hard with the Nepali government. The detailed project report (DPR), which was being formulated by the two countries, was abruptly put on hold two years back after Nepal showed its disinterest in the dam.