Posterity Will Not Forgive: Kosi Disaster
By DR. AB THAPA
The Kosi River is now on the verge of shifting to the east far away from its present course. Posterity will never forgive us if our South Asian region is plunged perhaps into one of the world’s greatest catastrophes in terms of loss of life and property as a direct consequence of our negligence to timely address the Kosi flood problems despite the clear warnings of those involved in Kosi study about the imminent danger. We all involved in Nepal ’s water resources development activities would be blamed for such tragedy. Future generations would be raising accusing finger particularly at those institutions such as the Planning Commission, Ministries of Water Resources and Environment, and various other agencies professing to be concerned for the study and development of our country’s water resources. International institutions such as the ICIMOD, Winrock etc operating inside Nepal already for a long period in the field of water resources would perhaps be finding very hard to escape from the wrath of public and international community for having failed to provide timely advise to avert the Kosi disaster. It would be particularly annoying because the Kosi disaster could have been easily averted and the preventive measures instead of becoming the slightest burden to the nation would have on the contrary greatly helped to benefit the common people of Nepal struggling very hard for their livelihood.
Kosi Flood Problem
The Kosi River known as the river of sorrow of the Bihar shifted from east to west over 12O km in the last 200 years. In the past about 8000 sq. km. of lands had been laid waste as a result of the sand deposit. In course of shifting, many towns and villages were wiped out, and heavy losses of property, cattle, and human life were inflicted. Fortunately the embankments built few decades ago temporarily helped to check the lateral shifting of the Kosi. But at present the detention basin upstream of the barrage at Hanumannagar is almost full of sediments. Soon the embankments would be ineffective to control the Kosi floods.
Now the Kosi is on the verge of shifting to the east far away from its present course. The peoples of Nepal and India are heading for a flood disaster on an unprecedented scale. But only very few in Nepal and India appear to have realized the extent of this grave danger. It would be unfortunate if the Kosi swing to the east takes the life and property of millions in South Asia by surprise while the concerned institutions and agencies would merely be silent spectator.
Why Kosi Would Abandon Its Course?
The Kosi River brings every year an enormous quantity of sediments from its catchments in the mountains. Sir Claude Inglis an expert on Kosi had attributed the shift of the Kosi River channel to excessive sand load carried by the river. Leopold and Maddock considering Kosi behavior had stated that a braided stream will tend to shift laterally at a rate dependent on the rate of accumulation of material being deposited. As one course becomes higher than possible adjacent paths, the river would shift.
Data published in the American Society of Civil Engineering in March, 1966 indicate that in the period between 1938 and 1957 every year on an average about 100 million cubic meters of sediments used to be deposited on the Kosi River bed. The maximum such deposition was around Nirmali in India not far away from Hanumannagar. There was a very big change in sediment deposition pattern immediately after the completion of the Kosi barrage in 1963. The results of the Kosi River channel study for post barrage period have been published by V.C. Galgali, Central Water and Power Research Station, Pune (India), and Gohain & Prakash of Roorke University. All the past studies confirm that the Kosi River bed just upstream of the barrage has significantly aggraded due to sediment deposition. On account of ponding, sediment deposition had occurred, flattening the bed gradient. The bed slope of the river in the pond area was abut 0.61 m per km in the year 1956 prior to construction of the barrage, which became flatter to about 0.42 m per km in the year 1969, ie in six years of the functioning of the barrage. Studies were made to determine the sediment deposition based on post flood 1963 and 1970 surveys These studies indicated that about 35 million cu. m. sediments had deposited in the pond length of about 10 km upstream of the barrage, giving an average depth of about 0.4 m in about 8 years with a rate of bed level rise at about 0.05 m per annum.
Embankments Would be Ineffective
Embankments built a few decades ago temporarily helped to check the lateral shifting of the Kosi. The detention basin upstream of the Kosi barrage near Hanumannagar is going to be very soon full. After that the embankments would be ineffective to prevent the lateral shifting of the Kosi. It is predicted that the Kosi would again take its 1732 course. The farthest position of the new course of the Kosi is expected to be about 120 km away from its present course. The swing of the Kosi river to the east could be sudden and almost unexpected because nobody yet exactly knows when it is going to happen. The people would be completely taken by surprise. So the loss of life could be very high. In a similar type of 1938 flood incident of the Yellow River in China the number of people killed alone was about half a million. It does not need to be further explained that such shifting of the Kosi to the east would be a biggest disaster for the whole region. Generally the flood damages are temporary in nature but the Kosi flood damages would be widespread and also permanent in nature. Mr. Shilling Feld . an expert on Kosi, has warned a longtime ago that the eastward movement of the Kosi will be in one big swing accompanied with great loss of life and property.
Situation Already Alarming
Few years after the commissioning of the Kosi barrage there was a big flood in 1968. A discharge of about 25,000 cumecs was recorded. The flood at that time did not pose serious threat. At present the conditions might be altogether different. It is said that whenever the discharge exceeds 9,000 cumecs which is fairly common the whole area between the embankments is submerged. Such observations raise the fear that a flood similar to 1968 flood in magnitude could prove to be catastrophic. It should be further remembered that the 1968 Kosi flood is not exceptionally rare. A flood of this magnitude has already been observed twice within the last 50 years. Fortunately in course of the last 35 years the maximum flood discharge of the Kosi River has not exceeded 16,000 cumecs.
Resolving the Flood Problem
Provision of dams in the drainage area with very big storage volume is the only lasting solution to the Kosi flood problem. It is the opinion of the renowned experts and scientists involved on the Kosi study in the past. We can draw such lesson from the past experience of China also. It can be confidently said that there are not any substitutes for the large storage dams to control the Kosi floods. The storage dams should be provided in time. Unfortunately some peoples in Nepal and India have misgivings about the Kosi dams. Such misgivings are unfounded and they are often the result of present global disenchantment with the high dams particularly for the generation of hydroelectricity. In case of the Kosi dams this type of notion is completely misplaced. The life and property of too many peoples in Nepal and India would be at great risk if the Kosi dams are not built in time.
1997 Indo-Nepal Study Agreement
Nepal had signed an agreement with India in 1997 to conduct jointly the detailed study of the Sun-Kosi Dam Project, Kosi Dam Project and the Navigation Canal linking Nepal with the seaport. It is explained hereinafter that the Sun-Kosi dam project would have to be implemented at the earliest if the life and property of millions in Nepal and India are to be protected from the devastation caused by the shifting of the Kosi river to the east far away from its present course.
Why Sun-Kosi Dam Project First?
There are three compelling reasons why the implementation of the Sun-Kosi Dam Project would have to precede the construction of the Kosi Dam Project. Firstly, it can be said with certainty that at least one storage dam should be built either across the Kosi or its biggest tributary the Sun-Kosi in very near future to avert Kosi flood disaster. Secondly, it would not be possible to build later on the Sun-Kosi Dam Project if the Kosi Dam Project is implemented first. The site chosen for the Sun-Kosi dam would be submerged in the Kosi Dam reservoir. But fortunately the Kosi Dam Project can be implemented even after the completion of the Sun-Kosi Dam Project. Thirdly, it would take a very long time just to complete a fairly satisfactory detailed study of the mammoth Kosi Dam Project which is going to be one of the largest high dam projects in the whole world. Thus for the next few decades we would have to mostly concentrate on the problems related to detailed study of the Kosi Dam Project. Let us not forget that the People Republic of China was struggling for more than 20 years to complete the detailed study of the Three Gorges Project which is virtually on a par with the proposed Kosi Dam Project in magnitude and engineering complexity. It would, however, be quite risky to delay for a long duration the implementation of the project earmarked to control to the Kosi river to avert flood disaster. As a result, we should be concentrating in near foreseeable future almost exclusively on the implementation of the Sun-Kosi Dam Project which is also considered to be the lifeline for the people of Nepal desperately in need for increasing the agricultural productivity through extensive irrigation development.
Great Significance of the Sun-Kosi Project
The necessity of the irrigation development on a large scale in Nepal had been keenly felt since the middle of 1960s. Bearing in mind such necessity of large scale irrigation development, the experts of the Food and Agriculture Organization ( FAO) and the Government of Nepal had begun the study of the Sun-Kosi Terai Project in 1965 to determine the possibility of irrigation development in the Eastern Terai Plain by diverting the abundant water of the Sun-Kosi River. The final feasibility report was submitted in October, 1972.
The feasibility report makes it perfectly clear that the people in Nepal are mostly dependant for their food supply and livelihood on a narrow belt of cultivated land in Terai. The potential new land for cultivation is very limited in Nepal. Thus, there is a need to raise agricultural productivity by intensification; i.e. by increasing the average cropping intensity. The Sun-Kosi diversion could help to provide sufficient water round the year to increase the cropping intensity as well as the per hectare yield, as a result, the agricultural production could be substantially increased.
In Conclusion
The imminent danger of the Kosi floods to be triggered off by the sudden change of its course is too great to be ignored. Tens of thousands of people in Biratnagar area might perish and many times more could be rendered homeless in the future Kosi floods. People in far greater number would be affected in north-east Bihar also. Luckily, the implementation of the relatively small Sun-Kosi Storage Dam Project at the earliest could provide effective shield from the threat of the Kosi floods for about next 40 to 50 years. If future studies confirmed that there is room for doubt about the capacity of the Sun-Kosi Storage Reservoir alone to control the Kosi floods, we could also think of implementing the small Tamar-1 Storage Dam Project side by side with the Sun-Kosi Dam Project. Thus, we need not rush to implement in very near future the mammoth Kosi Dam Project which has been considered to be indispensable for the safety of life and property of millions in our region.
(Dr. Thapa writes on water resources)
