‘Consider studies of river basins for audits, building new structures’
The washing away of the colonial bridge on the Savitri river on the Mumbai-Goa highway near Mahad has raised questions over efficacy of the way bridges and barrages are being planned and built on our rivers.mumbai Updated: Aug 04, 2016 17:44 IST
The washing away of the colonial bridge on the Savitri river on the Mumbai-Goa highway near Mahad has raised questions over efficacy of the way bridges and barrages are being planned and built on our rivers. Experts working in the water sector told HT that it was not enough to just conduct structural audits of the old, colonial bridges to ensure its safety. They said that hydrological study of river basins is a must for any new construction on the rivers as well as audit of old structures.
“An overall hydrological study of a river basin has to be carried out before planning new structures on the river like barrages and bridges. Similarly, a safety audit of existing old structures will not work unless the changes in the river basin are counted for,’’ said Parineeta Dandekar, associate co-ordinator with South Asia Network for Dams, River and People (SANDRP).
She added, “Climate change is for all to see. The rainfall days have reduced but intensity of rainfall in shorter duration is much higher. This has an impact on the velocity of pressure exerted on such structures. In a small basin like Savitri, which comes under a high rainfall catchment area, the pressure is all the more.’’
The catchment area of the Savitri river had registered in Mahad had received ten times more rainfall than normal in 24 hours on Wednesday between 230 and 260 mm. Mahableshwar, where the Savitri river originates had recorded 790 mm of rainfall since Monday against its average of 63 mm. The river was in a spate as a result.
Chief Minister Devendra Fadnavis has called for a judicial probe into the Mahad accident and a structural audit of all 36 bridges along the Mumbai-Goa highway.
Pradeep Purandare, water expert and former associate professor with the state’s Water and Land Management Institute (WALMI) agreed with Dandekar. He said that there is a mechanical response to the way we audit and build bridges on rivers.
“It’s not enough to just look at traffic estimates, weight of vehicles that will run on the bridge. What about lateral pressures on such structures.. the sand mining that is carried out often illegally on the banks and has an impact on the flow of water. Climate change that is affecting our river basins also has to be looked into but is not considered unless big dams are being built,’’ said Purandare.
Structural engineers had told HT that the alignment of the new bridge built in 2001, could have also contributed to the collapse of the colonial bridge as it had narrowed passage of water, increasing pressure on the pillars of the bridge.