Experts offer tips to check Kosi bund breach
PATNA: While breach in the eastern Kosi afflux embankment at Kusaha in Nepal around three and half years ago caused catastrophic flood in six districts bordering Nepal and brought into focus the vulnerability of physical structures created as part of the Birpur barrage system, people living in the Kosi basin districts, along with the state’s water resources department (WRD), continue to remain burdened by a plethora of other problems.
As state WRD minister Vijay Kumar Choudhary said in his inaugural lecture at a session of technical presentations on ‘Holistic Solution to the Problems Related to Kosi Floods’ organized by the WRD here on Sunday that the Birpur barrage and the network of canal system has revolutionized agrarian scene in the Kosi basin by facilitating three-crop agriculture activities, problems still remain unresolved.
The problems include persistent annual floods, unchecked erosion caused by the river, routine and yet alarming annual loss of arable land due to erosion, annual silt deposits, and uncertainty with regard to the protection of embankments. Breaches had occurred six times at various points in the embankments of the Kosi- Dalwa (1963), Jamalpur (1968), Bhatania (1971), Baharua (1980), Nauhatta (1984) and Jogania (1991), Choudhary added.
Nayan Sharma, head of the department of water resources and management at IIT Roorkee and Wolfgang-Albert Flugel, head of the department for geo-informatics, hydrology and modelling at Friedrich Schiller University (Germany) suggested solutions to the problems.
While Flugel dwelt largely on the need to prepare and collate hydrological information base on the watershed of the Kosi as an aid to prepare hydrological response model to the problems, Sharma made suggestions with regard to the cost-effective work as against the hitherto practised cost-intensive physical model method that relies on construction of structures to address the problems. The latter also includes construction of spurs to deflect water back into the river.
According to Sharma, under the mathematical model in contrast to the physical model, the embankments could be protected with geo-mattresses (laying and insertion of sand-filled mattresses along the slopes of embankments to prevent their erosion by overtopping of water and to check entry of water into the embankment through holes).
Further, he suggested the use of submerged vanes in the river at points where erosion is caused since the submerged vanes lower the speed of water at the deeper layers of water current resulting in sedimentation. Also, porcupines could be used to facilitate sedimentation and reclaim eroded land, and the ‘jack jetty model’ could be used to channelize the river along its main course. “The problem points should be identified, and the points at which the work is to be started should be prioritized,” Sharma said, adding: “Dredging of the silt and sand from the course of the river is not a viable solution. It is also cost-intensive.”
State WRD principal secretary Afzal Amanullah said the delivery of experts has given an exposure to the department’s engineers to alternative ideas apart from giving their viewpoint on the problems to the Kosi Inquiry Commission.