‘Design based on flood intensity of 500 year return period’
*Protection to be provided to downstream structures
Mohinder Verma
JAMMU, Jan 9: Government of Union Territory of Jammu and Kashmir has informed the National Green Tribunal (NGT) that Tawi Barrage will not impact ecology of the river in any manner as adequate measures in this regard have been taken. Moreover, the barrage has been designed for flood intensity of 500 year return period, which is much more than the floods observed in September 2014.
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In a detailed report submitted to the green panel, the Chief Engineer, Irrigation and Flood Control Department has mentioned that Tawi Barrage envisages creating a pondage of 1.35 million cubic meters (MCM) capacity with pondage level of 297.8 meter.
“The under sluice gates will remain open for safe passage of water even during the lean discharge in the river. There will be no stoppage of water downstream of barrage at any point of time and therefore, there will be no effect on the ecology of the river”, the report said, adding “there will be no pondage of water during flood season when all the gates will be fully raised to allow flood water flow without any obstruction as such barrage will have no impact during flood conditions”.
About the concerns over potential flood risks from Tawi Barrage and RFD projects because of squeezing of riverbanks from both the sides, the Chief Engineer said, “existing width of waterway at Bikram Chowk Bridge is 300 meter which could safely pass the discharge during the 2014 floods. The total waterway provided at barrage has been designed based on one in 500 year flood return period which is much more than flood discharge during the 2014 floods”.
“The safe passage of the discharge during floods has been validated by the Physical Model Studies for Tawi Barrage conducted by the Indian Institute of Technology (IIT) Roorkee as such there is no risk of potential flood due to construction of Tawi Barrage”, the Chief Engineer said, adding “IIT Roorkee has provided a detailed methodology for operation of gates for various discharge conditions and a comprehensive plan for operation of gates has been suggested to maintain pond level in upstream of barrage and for managing the sediments”.
The comprehensive Standard Operating Procedure (SOP) for operation of gates during various discharge conditions will be incorporated in Supervisory Control and Data Acquisition (SCADA) system for operation of automatic gates.
“Due to automatic operation of barrage gates corresponding to various discharge conditions, an early warning in this regard will be transmitted by Early Warning System installed at Manwal Tawi Bridge to the SCADA system as such there will be no obstruction to flow during heavy floods”, the report said.
About the apprehensions that construction work on the central portion of RFD covering the river island could damage the ancient Ranbir Canal structure running underneath across the river, the Chief Engineer submitted that ancient Ranbir canal structure has outlived its life and stands abandoned since long.
“This structure has been replaced by a new RCC structure constructed in the year 1990 as such construction work on the central portion will have no effect on this new structure which has been constructed well before the river bed level and is running to its full capacity without any obstruction even after construction of RFD works”, the report said.
The Chief Engineer has further submitted that keeping in view the September 2014 floods and in order to avoid such incidents in future, morphological studies of River Tawi have been conducted by the Economic Reconstruction Agency (ERA) under World Bank funding.
“A Detailed Project Report for flood mitigation and comprehensive river management measures for Tawi Basin is under preparation by ERA through consultant Aqualogous-Oiltech JV and protection of structures to the downstream of Tawi Barrage has been considered in the DPR”, the Chief Engineer said, adding “the protection works will be provided in accordance with the provisions of the DPR”.
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