Outdated stormwater system and encroached nullahs increase risk of ‘urban flooding’ in Pune

Encroached nullahs, vanishing natural streams and faulty stormwater drainage lines are being cited as the main reasons for the increased incidents of urban flooding in Pune.

Written by Partha Sarathi Biswas , MANOJ MORE | Pune | Published: October 15, 2017 4:42 am
Pune rains, heavy rains in pune, pune encroachments, pune rain forecast, pune weather,  Pune Municipal Corporation (PMC),Geographic Information System (GIS) , pune news, indian express news   Rain continued to lash Pune on Saturday, a day after the city saw its third wettest day in a decade. (Express Photo By Sandip Daundkar)

A COUPLE of hours of torrential rain on Friday brought Pune to a virtual halt, and once again highlighted the danger of urban flooding that lurks behind the facade of ‘Smart Pune’. With heavy rain becoming more of a norm than an anomaly, experts and planners say incidents of urban floodings are likely to increase in the future. Encroached nullahs, vanishing natural streams and faulty stormwater drainage lines are being cited as the main reasons for the increased incidents of urban flooding in Pune.

Shrikant Gabale, head of the Geographic Information System (GIS) Cell of ETH Limited, has been studying the phenomenon of urban flooding and flash floods in Pune since the last few years. Gabale, who has identified over 60 flash flood points in the city in recent years, said, “A decade ago, there were hardly 20-odd such points,” he claimed. Flash flood points are areas that are prone to flooding after medium to heavy showers.

The increase in the number of flash flood points was due to the “faulty and non-scientific” stormwater drainage lines in the city, said Gabale. Stormwater drainage lines should be aligned to the gravitational slopes and the manholes provided should be at regular intervals, he said, adding that in Pune, he has identified many points where the drainage line and gravitational slope of water are in opposite directions. “Instead of manholes located every 30 metres, we have haphazard placement of manholes, which aggravates the problem, rather than tackling the threat of urban flooding,” he said.

Gabale said the stormwater drainage maps of Pune require immediate attention, and called for a re-survey of the system. “The maps should include flow directions and pipeline capacity of the system,” he said. The non-clearance of rubble also plagues the vital drainage system, causing it to overflow.

Incidentally, the revised development plan of Pune had pointed out the precarious condition of the stormwater drainage system in the city. The city has 23 river basins and 228 nullahs but currently, only 52 per cent of the existing roads have proper drainage. The report, submitted to the Pune Municipal Corporation (PMC), had recommended strategies to protect the natural drainage system, as well as for the desilting, rehabilitation and remodelling of the stormwater drainage system in the city.

Another major reason for urban flooding in Pune: the gradually disappearing natural streams and nullahs, which have been heavily encroached upon. Gabale’s study had shown how, on an average, 30-40 per cent of the natural streams in major basins of the city have vanished, and this has resulted in increased cases of waterlogging. In case there is an encroachment on its natural path, rainwater tends to accumulate on the roads, flooding them. The problem is acute in areas like Baner, which has seen large-scale development over the last few years.

City MP Anil Shirole said he has time and again asked the PMC to look into the issue. “We should identify the problem and take steps to solve it,” he said. The PMC, on its part, claimed the problem of waterlogging will be partially resolved within a few months, as the civic administration is implementing a ‘sewerage masterplan’ to counter the recurring problem of flooding. “Wherever the plan has been implemented, the problem of overflowing nullahs or stormwater drains has been addressed. The master plan had received the civic general body’s approval and the civic chief’s proposal for increased budgetary provision was also approved,” said PMC City Engineer Prashant Waghmare.

Conceding that nullahs have been encroached on, Waghmare said, “Because of schemes like gunthewari, implemented by the civic bodies, nullahs either got encroached on, or their course is changed.” PMC Superintendent Engineer Jagdish Khaore said under the sewerage masterplan, the civic body will survey each and every drainage line, to ascertain the exact type of drainage pipeline needed in that area. “Currently, we are surveying Aundh, Baner, Bopodi and Vithalwadi basins… we will check the diameter of the drainage pipeline as per the projected population in 2027, 2037 and 2047, and then install the right one,” he said.

Admitting that many drainage lines were almost 25-40 years old, Khaore said, “In gaothan areas, drainage lines are at least 40 years old, but in new areas, they are about 10 years old.” He added, “One lakh drainage chambers in the city “are being surveyed with the help of GIS…”.

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