GUWAHATI, July 24 � The submerged heaps of sand deposits in the Brahmaputra river system are at the root of the river�s unremitting bank erosion process, observed noted river engineer Prof Nayan Sarma. Prof Sarma is presently the Head of the Department of Water Resources Development & Management, Indian Institute of Technology (IIT), Roorkee.
He maintained that it is of prime importance to urgently take up the process for tackling the channel instability behaviour of the Brahmaputra River to achieve gradual channelization in a phase-wise manner.
This can be achieved by adopting a strategic approach to systemically bring about subsidiary channel closures combined with effective stream bank erosion control. Such a strategy will require adoption of innovative sedimentation inducing river training techniques, he maintained.
�From a satellite imagery based analysis by my team at IIT Roorkee, it could be estimated that a total land area of about 1700 square kilometres has been eroded by the Brahmaputra and its major tributaries during the period 1990 � 2007,� Prof Sarma said.
This land loss is accompanied by sharp rise in braiding intensity of the Brahmaputra, which is reflected in increased flooding and overtopping of the flood embankments, he said.
To him, the annual average sediment load of the river has now reached a value of about 800 million tonnes, a good part of which gets deposited in the riverbed during the receding flood stage.
He argued that for more durable permanent solution, it is prerequisite to undertake effective catchment area treatment extensively through implementation of soil conservation measures. The approximate time frame of about 30 to 40 years may be required for achieving some sort of reasonable stabilization of the river morphology, he said.
Prof Sarma told this correspondent that this sedimentation process uses to give rise to big heaps of sediment deposits on the streambed submerged in the flow.
Furthermore, he said, the Brahmaputra basin has the highest specific yield in the world of the order of about 3 cusec per square mile.
The increasing sediment ingress, much beyond its transportation capacity, from the watershed areas has also proved to be a major cause for the unbridled channel instability in the Brahmaputra river system.
The likely prospects of the ongoing malaise afflicting the Brahmaputra river system is expected to reach difficult intractable state in a few decades time, which will very adversely affect the entire North Eastern Region of India in many spheres.
On top of all these, there is a very serious apprehension that the possible occurrence of a big earthquake superimposed with the ongoing bank erosion, will spell disaster for the Brahmaputra basin and the NE Region with major course changes and channel avulsions.
This is a very grim scenario for the NE Region that is likely to unfold in a few decades time transforming the Brahmaputra valley as virtually uninhabitable and making bulk of the population destitute, he said.
Due to wanton deforestation and rising urbanization in the catchment area, the soil erosion process is likely to accelerate and the flow volume of surface runoff will further increase resulting in sharp rise of the flood hydrograph.
In contrast to the holistic strategy mentioned above, the approach presently adopted for the Brahmaputra River is based on use of impervious spurs, flood embankments with and without use of geo-tubes, porcupines, bank pitching with boulders etc.
Notably, the present approach is focused on a site specific localized tackling of stream bank erosion in a piece-meal manner without a comprehensive strategy to deal with the problem in totality. Evidently, such a piece-meal approach simply shifts the problem to another river location and at the same time remains vulnerable to future threat from the river as happened at Dibrugarh this year.
In contrast, Prof Sarma said, the proposed combination of submerged vanes with jack jetty is conducive to create favourable flow condition to bring about gradual closure of drifting subsidiary stream channels of the Brahmaputra for ultimate achievement of channelization in a phase-wise manner.
GUWAHATI, July 24 � The submerged heaps of sand deposits in the Brahmaputra river system are at the root of the river�s unremitting bank erosion process, observed noted river engineer Prof Nayan Sarma. Prof Sarma is presently the Head of the Department of Water Resources Development & Management, Indian Institute of Technology (IIT), Roorkee.
He maintained that it is of prime importance to urgently take up the process for tackling the channel instability behaviour of the Brahmaputra River to achieve gradual channelization in a phase-wise manner.
This can be achieved by adopting a strategic approach to systemically bring about subsidiary channel closures combined with effective stream bank erosion control. Such a strategy will require adoption of innovative sedimentation inducing river training techniques, he maintained.
�From a satellite imagery based analysis by my team at IIT Roorkee, it could be estimated that a total land area of about 1700 square kilometres has been eroded by the Brahmaputra and its major tributaries during the period 1990 � 2007,� Prof Sarma said.
This land loss is accompanied by sharp rise in braiding intensity of the Brahmaputra, which is reflected in increased flooding and overtopping of the flood embankments, he said.
To him, the annual average sediment load of the river has now reached a value of about 800 million tonnes, a good part of which gets deposited in the riverbed during the receding flood stage.
He argued that for more durable permanent solution, it is prerequisite to undertake effective catchment area treatment extensively through implementation of soil conservation measures. The approximate time frame of about 30 to 40 years may be required for achieving some sort of reasonable stabilization of the river morphology, he said.
Prof Sarma told this correspondent that this sedimentation process uses to give rise to big heaps of sediment deposits on the streambed submerged in the flow.
Furthermore, he said, the Brahmaputra basin has the highest specific yield in the world of the order of about 3 cusec per square mile.
The increasing sediment ingress, much beyond its transportation capacity, from the watershed areas has also proved to be a major cause for the unbridled channel instability in the Brahmaputra river system.
The likely prospects of the ongoing malaise afflicting the Brahmaputra river system is expected to reach difficult intractable state in a few decades time, which will very adversely affect the entire North Eastern Region of India in many spheres.
On top of all these, there is a very serious apprehension that the possible occurrence of a big earthquake superimposed with the ongoing bank erosion, will spell disaster for the Brahmaputra basin and the NE Region with major course changes and channel avulsions.
This is a very grim scenario for the NE Region that is likely to unfold in a few decades time transforming the Brahmaputra valley as virtually uninhabitable and making bulk of the population destitute, he said.
Due to wanton deforestation and rising urbanization in the catchment area, the soil erosion process is likely to accelerate and the flow volume of surface runoff will further increase resulting in sharp rise of the flood hydrograph.
In contrast to the holistic strategy mentioned above, the approach presently adopted for the Brahmaputra River is based on use of impervious spurs, flood embankments with and without use of geo-tubes, porcupines, bank pitching with boulders etc.
Notably, the present approach is focused on a site specific localized tackling of stream bank erosion in a piece-meal manner without a comprehensive strategy to deal with the problem in totality. Evidently, such a piece-meal approach simply shifts the problem to another river location and at the same time remains vulnerable to future threat from the river as happened at Dibrugarh this year.
In contrast, Prof Sarma said, the proposed combination of submerged vanes with jack jetty is conducive to create favourable flow condition to bring about gradual closure of drifting subsidiary stream channels of the Brahmaputra for ultimate achievement of channelization in a phase-wise manner.
