Long-term safety of KLIS barrages need re-engineering: Study
Hyderabad: The flood protection measures may be in place at Sundilla, Annaram, and Medigadda barrages of the Kaleshwaram Lift Irrigation Scheme (KLIS) but if the latest model studies of the Medigadda barrage, and a recent previous study for Annaram are anything to go by, the medium and long-term stability and safety of the barrages will require a massive engineering effort to protect the structures from the vagaries of floods in Godavari river.
The latest model studies for Medigadda, and the one for Annaram, have shown gaping faults in the original designs of the two barrages, and according to engineering experts, the same would also hold good for the Sundilla barrage.
All three barrages experienced various states of distress and damage springing leaks from under their foundations with the worst damage occurring at Medigadda with a portion of the barrage cracking and sinking. The model studies for both barrages took into account various flow parameters including free flow state, and with the gates lifted to specific heights.
According to sources, the model study for Medigadda at IIT Roorkee on June 13 and 14, and again on June 27 and 28, has once again demonstrated the inadequacies in design of the downstream structures of the barrage including its apron, and flood force dissipation arrangement using cement concrete blocks. It is now believed that because of these design shortfalls, water from the upstream side of the barrage forced its way from under the foundations causing serious damage to Block 7 of the Medigadda barrage.
Once the model study was completed, experts who conducted it have recommended not only an extension of the downstream apron from its current 7.98 metres to 48 metres but also design it in such a way that a three-metre pool of water stays on the extended apron to serve to dissipate flood water energy on the downstream side. “In effect, what the barrage urgently needs is a 48-metre long stilling basin made of cement concrete bed. This in itself will require new designs, and will be a major construction activity,” an irrigation engineer said.
It may be recalled that a similar study for Annaram done at the Central Water and Power Research Station, Pune, too ended up in a recommendation of extending the structure on downstream side of the barrage for a total of 60 metres, but in this case, the stilling basin was recommended to have a total depth of 6 metres for effective flood force dissipation given the geographic requirements at the location.
Engineers working at Annaram had also informed irrigation minister N. Uttam Kumar Reddy about the need for the 60-metre long stilling basin during his recent inspection of the three barrages to check on the National Dam Safety Agency recommended interim flood protection measures.
The minister made it clear that the state government was following NDSA recommendations for this year’s flood season, and long-term protection measures would follow after the end of the monsoon floods in Godavari river, and expert advice from the NDSA would be sought for the same.