Nov 17, 2006

By DR. AB THAPA

Universities and academies are seen playing in most of the countries very important role in shaping national policy on socio-economic development. They are usually in forefront in helping to resolve complicated problems facing the country. Nepal is now going to confront with a new type of problem. It is the Kosi flood problem. The Kosi river is on the verge of abandoning its present course and shifting to the east far away from its present position, hence the life and property of millions of peoples in our region are at great risk.

The Kosi river flood control problem, beyond all doubt, has emerged as the most important task before us requiring immediate attention of the whole country. Unfortunately only very few of us are aware of it. The Kosi problem is too complicated and vast to be handled solely by a single institution in Nepal . It need not be explained that universities, academies and various national and international institutions involved in the field of water resources development of our country and other socioeconomic sciences should come forward to help to resolve the Kosi flood problem.

River of Sorrow

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.

All the elderly people living in the Saptari district not far away from the Kosi river would not have much difficulty to recall that some 50 years ago the channel of the Kosi river flowing across the Sunsari district from north to south was gradually shifting laterally from east to the west. The river was already quite close to Hanumannagar. It is reported that by that time the Kosi. River debouching into the Terai plain at Chatra and joining the Ganges River near Kursella in India had already laid waste about 500 square miles of lands in Nepal alone. People living in the eastern part of the Saptari district were panic stricken. They were leaving their ancestral homes in thousands to find shelter at safe places far away from their villages carrying with them whatever few things they could take with them. The headquarter of the Saptari district at Hanumannagar was swiftly moved to Rajbirag which was at a safe distance away from the Kosi River. Fortunately the shifting of the Kosi River course to the west was held in check by the embankments built on either side of the river some 50 years ago. Now all those who are involved in the Kosi River study are saying that the embankments built to protect the life and property of millions in India and Nepal might have already outlived their usefulness. What is going to happen the next? Every common man would be expecting to get an answer. Perhaps it is of interest to all of us to know why the Kosi River changes its course.

Sediment Deposition

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 the 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.

Alarming Situation

All the past and present studies and the very recent observations indicate that the Kosi is quickly turning into a hanging river and we are heading for an unprecedented flood disaster. Such flood disaster would not be just one time event. Like the Yellow river floods disaster in China in the past, the ferocious floods of the Kosi would also be frequently hitting particularly our Sunsari district and the North Bihar wiping out towns and villages, and laying vast area of lands bare with sand deposits. The eastern and the southern boundaries of the flood-affected area could extend upto the Mahananda river and the Ganges respectively. India 's railway and roadway linkages with her northeast states could also be severed. In a similar type of China 's Yellow river 's latest flooding in 1938 the number of persons killed alone was about half a million. After this flooding big storage dams were built to control the Yellow river floods. The river is now completely regulated. There are no more flood damages. It is stated in CHINA DAILY (October 16, 1998) that the Yellow river dams have helped to save flood damages as of now of about US $ 50 billions.

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 any 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.

If the Kosi River changed its course to the east, the flood-affected area of the Kosi in the past estimated at about 8,000 sq. km could again be laid bare with sand deposits within a certain period by the combined effect of the Kosi floods that bring big quantity of sediments and the shifting of the main river course from one channel to another. The changing of the river course is the distinguishing feature of breaded rivers like the Kosi.

In Conclusion

Mr. F.A. Shilling Feld, a renowned expert on Kosi study, had made a chilling forecast a long time ago “ The westward movement of the Kosi oscillation (in the past) is slow and is in a series of steps, each of which is attended with damage to property of temporary nature. The eastward movement (in future) of the oscillation will probably be accompanied with great loss of life and property.” The Kosi floods control problem has already emerged as the biggest challenge facing our country.

Indeed, the Kosi River is posing a serious threat to life and property of millions in Nepal and India Solutions to the Kosi floods problem should be quickly found. Our universities and academies should direct their activities to help to resolve the imminent Kosi flood problem.

(Dr. Thapa writes on water resources)