[Assam] Kosi Deluge: dredging an impossible solution
Chan Mahanta
cmahanta at charter.net
Tue Sep 16 12:36:21 PDT 2008
>8. Kosi Deluge: dredging an impossible solution
> Posted by: "sgvombatkere at hotmail.com" sgvombatkere at hotmail.com mediavigil
> Date: Mon Sep 15, 2008 10:35 am ((PDT))
>
>Reference the discussion on dredging the Kosi channel, may I point out
>that the annual sediment load of Kosi is estimated at 115 MILLION
>cubic metres. Even at some point upstream where the sediment could be
>less, the proponents of dredging might like to calculate HOW MANY 7
>cum vehicle loads that would take, propose WHERE the dredged material
>would be dumped, check WHETHER the State of Bihar can muster that many
>vehicles to move out the dredged material EVERY YEAR, and check
>WHETHER there will be road space remaining for other vehicles not
>engaged in transporting the dredged material. It is simply not practical !
>
>However, dredging at local levels may be effective for limited periods
>of time because the river is not one that can be "controlled" or
>"trained". But why are we talking about dredging when the cause of
>the problem is the embankments themselves?
>
>Maj Gen S.G.Vombatkere (Retd)
Dear Sudhir:
Good to hear from you.
I am guilty of highlighting the issue. It was in response to a dam
proponent's verdict that
if reservoirs and rivers require dredging, it has to be done--or
something in that vein; similar to other dam/embankment proponents'
laments that it is all a problem of govt. officials who are derelict
in their duties but remaining unaccountable -- leading to clogged
safety releases or silted reservoirs -- and not bad or unwise
engineering.
I posed the question that IF dredging is A solution, if not THE
solution, then why does it not get done?
Surely a lot of dredging can be done even by human labor wielding
hoes and carrying the dirt on head-baskets during the dry season.
And if dams and embankments were built with the assumption that
there would be no silting or as much silting as it has turned out to
be, then de-silting must be considered as A SOLUTION .Question is
WHY has it not been done? Not even tried. Would we NOT want to know
WHY?
Mind you now, the silting estimates over the greatly now greatly
widened and extremely shallow riverbeds do NOT necessarily mean that
all that silt will have to be dredged every season. If even a
narrow channel with a reasonable depth can be maintained it will
alleviate the conditions of water spread enormously. Even though the
rivers will not be " CONTROLLED" or "TAMED" its bank eroding and new
channel creating tendencies will be greatly impeded. It may not hold
true for the Kosi -- I am not familiar with its conditions. But
there certainly are rivers in Assam that can benefit from dredging.
Many tributaries of the Brahmaputra did not use to be as shallow a
few decades ago as they are now or cause damaging floods that did
not use to in the past. If a dredged and straightened channel is
created, it will greatly eased the flooding. I suspect it will be
true to some Bihar rivers as well.
Where does the excavated silt go to ? Good question. There could be a
number of answers to that. But I will focus on one: I don't know
about Bihar, but in Assam the demand for landfill is extremely high.
So much so that in Guwahati, which like most Indian cities have
plenty of laws but no governance , people have obliterated a number
of minor hills - illegally -- that dotted the metro area--for
landfill to build on. In the process they also have wiped out the
numerous wetlands that were home to water-birds and animals and
plants, not to mention the water detention facilities. So, now,
every time it rains even moderately hard, the whole city gets
inundated and literally floats in its own excreta. Even in rural
areas of Brahmaputra Valley, like where I grew up, there is an
enormous demand for fill-dirt. High ground there is in short supply
for building and year-round agriculture. Most of the ground there is
low lying - serving only as rice growing areas, producing just one
crop a year. Some of it can definitely be filled, without creating
adverse conditions. When the British built roads and railroads, they
had to get the fill material from surrounding areas, creating useless
swamps that neither can be used for rice growing, nor for
fish-farming. Some of that could be filled and reclaimed. Some fill
material can be deposited to the shallower braids of the river that
will be abandoned if a stright and deepened channel is created.
Returning to the point--Assam and Bangladesh to the south and west
requires great amounts of landfill material. They could be put on
river barges ( not trucks and not even on rail wagons) and
transported where the demand is. But first the Brahmaputra needs to
be dredged so that a year round deep channel is available for barges
to ply from eastern Assam to the Bay of Bengal, like it once was and
which the British used very effectively to build its empire in the
sub-continent.
Then comes the question of undermining bridge columns. But that is a
non-issue for the Brahmaputra. I
think there are all of four bridges over the Brahmaputra in Assam.
Besides if these bridges were supported by piers which could get
undermined by dredging 3 meters or so of silt or even original river
bed, then those bridges ought to be demolished first to begin with.
So river dredging in Assam is not an outlandish or unrealistic
concept. It has far too many merits to be summarily dismissed as an
impossibility. But it is NOT something to argue FOR in defense of
embankment building or mega dam building. That is the difference.
Best.
Chandan
At 4:51 PM +0000 9/16/08, WaterWatch at yahoogroups.com wrote:
>There are 10 messages in this issue.
>
>Topics in this digest:
>
>1. A River's Rage
> From: mediavigil at yahoo.co.in
>
>2a. Time to Get united:Re: CRIMINAL MEDICAL NEGLIGENCE AND DEATH AT SAHA
> From: mishrajournalist
>
>3a. Re: Kosi River shifting
> From: Bhavanishankar Benkipur
>3b. Re: Kosi River shifting
> From: rina mukherji
>3c. Re: Kosi River shifting
> From: vishwanath s
>
>4. Press Release : WAFED representatives met Prime Minister Prachanda b
> From: wafed
>
>5. Rising Sea Level
> From: Billy Haliday
>
>6a. Re: Kosi's tragedy: Blunder after blunder
> From: Bhavanishankar Benkipur
>
>7. Dam(n) Kosi?
> From: ashok kumar
>
>8. Kosi Deluge: dredging an impossible solution
> From: sgvombatkere at hotmail.com
>
>
>Messages
>________________________________________________________________________
>______________________________________________________________
>________________________________________________________________________
>8. Kosi Deluge: dredging an impossible solution
> Posted by: "sgvombatkere at hotmail.com" sgvombatkere at hotmail.com mediavigil
> Date: Mon Sep 15, 2008 10:35 am ((PDT))
>
>Reference the discussion on dredging the Kosi channel, may I point out
>that the annual sediment load of Kosi is estimated at 115 MILLION
>cubic metres. Even at some point upstream where the sediment could be
>less, the proponents of dredging might like to calculate HOW MANY 7
>cum vehicle loads that would take, propose WHERE the dredged material
>would be dumped, check WHETHER the State of Bihar can muster that many
>vehicles to move out the dredged material EVERY YEAR, and check
>WHETHER there will be road space remaining for other vehicles not
>engaged in transporting the dredged material. It is simply not practical !
>
>However, dredging at local levels may be effective for limited periods
>of time because the river is not one that can be "controlled" or
>"trained". But why are we talking about dredging when the cause of
>the problem is the embankments themselves?
>
>Maj Gen S.G.Vombatkere (Retd)
>
>
>
>
>Messages in this topic (1)
>
>
>
>
>
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