The Sorrow Of Bihar : Kosi River

October 29, 2008 at 10:06 pm 2 comments

Pls note: This Article was Writen in June 2004

The Sorrow Of Bihar : Kosi River

By Dr. AB Thapa

There  are  two  rivers   in  Asia,  which  were  known  in  the  past   as  the  rivers  of  sorrow.  The  Huang Ho   River  in  China , which is also called the Yellow River,  was   known  as  the  “Sorrow  of  China”.   Similarly,  the  Kosi  River  that  flows  from   Nepal  to  India was  known  as  the  “ Sorrow   of  Bihar”. Both  these  two  rivers  were   named  “River  of  Sorrow”  because  they   had  caused  widespread  human  suffering  in  the   past.  At  present,  the  Kosi  and  the  Yellow   River  have  nothing  in  common.  The  Yellow   River  is  already  completely  controlled, as a result, it   does not anymore  pose  threat  to  people.  The   Kosi  still  remains   totally  unregulated. At   present,  the embankments  built  on  both  sides  of   the  Kosi  few  decades  back  have  temporarily   helped  to  control  this  river.  It  is   feared  that  very  soon  the  Kosi  would   abandon  its  present  course  triggering  off  a   new  cycle  of  damages and  destructions.  After such incident,  the  Kosi  might  not  anymore  be  only   the  sorrow  of  Bihar.  It  could  be  the   sorrow  of  the West Bengal  and  Bangladesh  apart   from  the terrible  havoc  the  Kosi  floods could   be playing  with  the  safety  of  people  in   southeastern  Nepal.

In the Past

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 because 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.

The Kosi river is now on the verge of shifting to the east far away from its present course. The peoples of Nepal and India are heading for a natural disaster of an unprecedented scale. But it  appears that only   very  few in Nepal and India  have realized the extent of this 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  governments  of  Nepal  and   India  would  merely be silent spectator.

Rise  in Kosi  River Bed   Level

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  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

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.

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.

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 concluded that there are not any substitutes for the large storage dams to control the Kosi floods. Thus, our only recourse is storage dam. 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.

Learning  to Live  with   the  Floods

Some  people  in  Nepal   and  India  have   misgivings  about  storage   dams.  They  regard  that  we  should  learn  to   live  with  the floods, therefore,  it  is  not   necessary  to  build   storage  dams  to   control  the  floods.  The  core  issues   often    raised    against   the  flood  control   embankments  and  dams  in  Kosi  drainage  area    do  not  appear  to be  realistic.  Some   subscribe  to  the principle  that  the Kosi  should    get  back  its  original  route  to  the   Ganga.   One  would  certainly be  at  a  great   loss  to  determine  the  original  route  of   the  Kosi   to  the  Ganga.  The  Kosi   route  had  shifted   from   east  to  west    over  a   distance  of  120  kms   in   the  last  200  years.

In  almost  all  the   cases  when  there  is  surplus  water  in  the   river,  flooding  results. It  is  a  well known   phenomenon   in  hydraulic  engineering.. The   Elbe   and  Rhine  floods  reported  few  years back  in our   newspapers come  under  this  category.  The Yantze  River   floods  are  also of  similar  nature.  The  flood   damages  are  not  permanent  in  nature.  Some   people  try  to  attribute   future  Kosi    floods  also   to   this  type  of   hydraulic  phenomenon.   Unfortunately, the  Kosi  flood   feared   to   wipe  out    in  future     vast  area  of  densely  populated    lands  in  our  region   is   altogether    different  in  nature. Unlike  the above  mentioned   floods  in  Europe  and  China,  the  Kosi   flood  damages  would  be  virtually  permanent in   nature.

The  1997  Indo-Nepal   Study  Agreement

In 1997 an agreement was signed between Nepal and India to carry out feasibility studies of the Sun-Kosi project and the Kosi project along with a navigation canal linking Nepal with the seaport. This agreement is a substantial modification to the earlier understanding reached between the Prime ministers of Nepal and India that covered only the Kosi high dam. The modification was made based on the findings of Nepal explained to Indian side in the meeting. There is a very close interrelationship between the Sun-Kosi and the Kosi projects. This interrelationship required the inclusion of the Sun-Kosi dam project in the Kosi development. Even a simple analysis of both these projects clearly illustrates the following points that help to explain why the Sun-Kosi project should be built first,  and  as  a   result,   the  feasibility  study  of  the   Sun-Kosi  Project  had  to  be  completed  as   soon  as  possible. (a) The diversion of the Sun-Kosi river at Kurule is the most important project of Nepal for agriculture development in near future. .  It   can  be  said  based  on the Karnali  feasibility   study  that  North  Bihar   would  be  getting    for  free  about  65%   of   the   water  diverted  from  the  Sun-Kosi  reservoir  for    irrigation  in  Nepal’s  Eastern  Terai   as   return  flow.  Moreover,  the stored Sun-Kosi  water diverted   in surplus to the need for irrigation in Nepal  for  generation of   power  would also be freely available to irrigate vast area of lands in North Bihar. This very important  project  would be precluded forever after the completion of the  construction of the Kosi high dam project. Fortunately, the Kosi high dam project can be built even after the completion of the construction of the Sun-Kosi high dam project. (b)  The Kosi high dam along with a navigation canal to link Nepal with seaport is a very big project. Needless to explain that navigation canal would be  extremely important  for future development of Nepal  as well as North  Bihar. It will take long time to implement this project. But the Kosi river is on the verge of shifting to the east. The Sun-Kosi dam  project  could   control the Kosi floods in the interim period till the Kosi high dam is completed.   (c)  Very serious downstream degradation problems could  be expected to   arise after the completion of storage dam projects. It is due to release of clear water from the reservoir in big quantity. Such acute degradation problem was observed in Boulder dam of the USA. The river bed in the 77 mile canyon reach had been lowered between 6 and 14 feet. Owing to the exposure of rock ledges the river became stable. However, at   about 130 kilometers away, the riverbed rose by six metres necessitating the construction of very expensive flood control structures. Similar phenomenon could be expected after the completion of the Kosi high dam also. The Sun-Kosi high dam built to control the floods in the interim period could help to reduce downstream degradation. It could also help to determine with greater accuracy the volume of flood regulation storage.

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.”    It  is  hoped  that  the  governments of  Nepal   and India  would  take  up  the  Kosi  development   matters   seriously.

(Dr. Thapa writes on water resources)



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2 Comments Add your own

  • 1. VIKAS  |  November 11, 2008 at 7:45 am


  • 2. Sourav Saha  |  January 19, 2009 at 2:10 am

    since the construction of kosi barrage is responsible for the present threat of rise of kosi bed by depositing large amount of sediments, one of some only possible remedies is desedimentation of the river bed OR natural protection by afforestation so as to minimise the destruction that will cause by flood havoc.

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