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Tuesday, May 18, 2021

Lessons for Pune pour in from Chennai floods

A natural water stream is the path rainwater takes to drain into bigger water bodies. Using topographical sheets and Google earth imagery, the researchers have studied almost all the basins and the results are disturbing.

Written by Partha Sarathi Biswas | Pune |
December 6, 2015 1:11:02 pm

The flash floods in Chennai, which has claimed over 200 lives so far and caused massive damage to the city, is said to be the result of indiscriminate destruction of water bodies and natural streams in the city, among other things.

Cut to Pune. Over the last few years, the city has seen many flash floods, which town planners and experts blame on disappearance of natural streams and water bodies. They say that of late, the city has been witnessing floods even during medium rains, which is a cause for alarm as the city might go the Chennai way during heavy rainfall.

Geographically, the city of Pune lies in a valley with many small and medium streams meandering down its area to empty at the Mula-Mutha basin. In their study, researchers Tushar Shitole, principal of Mamasaheb Mohol college, and Shrikant Gabale, a PhD scholar, have identified six major basins that are active in and around the city – Ramnadi, Ambil Odha, Nandusi, Bhairoba nala, Wadki nala and Wagholi nala.

A natural water stream is the path rainwater takes to drain into bigger water bodies. Using topographical sheets and Google earth imagery, the researchers have studied almost all the basins and the results are disturbing.

Ramnadi Basin

Back in 2010, the tiny river of Ramnadi was in the news for the havoc its flash floods created in the Baner-Bavdhan area, leaving 11 people dead. The public outrage in its aftermath prompted authorities to say they would raze illegal encroachments as well as demarcate red and blue flood lines for the river. While majority of the encroachments were pulled down, the demarcation of red and blue flood lines (construction within these lines is not allowed) is yet to happen.

During the course of their research, Shitole and Gabale found that almost 20 per cent of the secondary streams draining in Ramnadi had vanished and the width of the stream had reduced by almost 15 per cent. Of the 416 streams draining into the Ramnadi, 106 have vanished while the rest are at threat of disappearing due to the construction boom in the area.

Along with Ramnadi, the tiny river of Devnadi in the neighbouring Baner area has also been under a lot of stress due to encroachment.

Local residents had even moved a PIL in the Bombay High Court the problem. Anupam Saraph of the Baner Balewadi Area Sabha said that although the High Court had asked for removal of sewage lines and debris from the area, the Pune Municipal Corporation (PMC) had failed to do so. “The rivers are the lifelines in maintaining the water cycle in the area. Since the civic body has taken up channelisation work which involves concretisation of Devnadi, the wells have dried up in the area. Incidents of heavy rains invariably leads to flooding as the water is neither able to seep into the ground nor able to flow along the body of the river,” Saraph said.

Ambil Odha basin

In June 2013, flash floods near Shindewadi on National Highway 4 washed away a woman and her child. According to Gabale, the flash floods in this region were caused due to the closure of the waterways in the upper reaches of the rivulet Ambil Odha, which happens to one of the most important tributaries of the Mutha river. With 40 per cent of the first-order streams of the Ambil Odha lost forever, the researchers say, danger of flash floods in this area remains real. “These are the waterways which the rainwater take for surface run-off and their disappearance is dangerous for the local hydrology of the area and can lead to flash floods,” says Gabale. The district administration had taken up the issue of removing unauthorised construction in the area but the threat of flash floods still remains.

Wagholi-Kharadi basin

The heavy rains which lashed the city towards November-end caused deep distress for residents of Lohegaon, Dhanori and nearby areas. Waterlogging was reported from numerous areas, causing severe damage to vehicles and property. This area, home to huge construction boom, has also seen some of the largest loss of water streams.

Local resident Sameer Patil talks about how they had to pull down a compound wall as the water level was fast accumulating there. “Even during moderate rains, water-logging is a problem in the area. However, when it started raining continuously, the water level was fast increasing. We had no other way but to pull down the wall to allow the water to flow through,” he says.

This, town planners and geographers say, was a clear sign of the vanishing water streams in the area. In the Wagholi basin area, 34.78 per cent of the streams have vanished due to unplanned growth. Similarly, the Bhairoba Nala and Wadki Nala, which traverse through Hadapsar and its neighbourhood areas, have lost 22.73 and 16.56 per cent of their streams. With construction boom continuing unchecked in these areas, locals fear a Chennai-like situation here.

“There is no space left for the water to drain out due to construction of embankment walls. The magnitude of flooding can be reduced by allowing channels for the water to pass through,” Shitole says.

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