Friday, August 29, 2008

Rain: five tanks on the outskirts of Bangalore overflow

The Hindu : Front Page : Rain: five tanks on the outskirts of Bangalore overflow
Bangalore: Rainwater partially overwhelmed some 100 houses on either side of the Hebbal valley as five major tanks, beginning with the Bettahalasuru tank near the Bengaluru International Airport, overflowed late Wednesday night.

Low-lying areas such as Byraveshwaranagar, Hennur Garden, Vaddarapalya, Kothanur, Nandagokula Layout, Patel Garden and so on were waterlogged. Although rain ceased in the early hours of Thursday, the water level is yet to recede at many places.

Bruhat Bangalore Mahanagara Palike (BBMP) Commissioner S. Subramanya said that all the major five interlinked tanks — Bettahalasuru, Agrahara, Kogilu, Yelahanka and Rachenahalli — filled as the area received 352 mm rainfall in the last three days. Had the same quantum of rain occurred in the erstwhile BMP areas, the consequences would have been unimaginable.
Cascading effect

The Bettahalasur tank spilled over first on Wednesday midnight when it rained 110 mm and this had a cascading affect on the other tanks.

Meanwhile, Hebbal and Nagawara tanks in the city overflowed.

All these resulted in the flooding of the Hebbal valley which connects to Kalkere tank, he said.

Dr. Subramanya said the BBMP personnel had to cut open the Kalkere tank, allowing water to flow further to pre-empt flooding of some of the newly added areas to the BBMP. “It will take at least 24 hours for water to completely recede if it does not rain again.”

Executive Engineer (Byatarayanayapura zone) M.P Somesh said the stormwater drain had the capacity to take only 55 to 60 mm rainfall and could not cope with the doubled inflow.

Two other factors contributed to the flooding: diversion of water near Hennur Bande, where the drain is being refurbished, and the bottleneck caused by the narrow pipeline (only 2 to 4 metres wide compared to the 42-metre width of drain) below a nearby railway track, said Mr. Somesh.

Dr. Subramanya said there was no damage as there were not many constructions, particularly on both the sides of the Hebbal valley, and this allowed the water to take its natural path.

It would have been a different situation had the Vrushabhavathi valley experienced a similar inflow, he said and pointed out that encroachment had greatly narrowed the valley.

He warned against complacency saying the situation might worsen if the catchment areas of these tanks received heavy rain consecutively.
River or road?

Overnight, the roads in Patel Gardens, Kothanur, one of the affected areas, turned into a flowing river.

There was water all around and one could not make out where the road ended or the sidewalk began.

“I could not send my five-year-old to school as the van could not access our road,” said Pavitra H. Her daughter Shraddha did not mind and joined a gleeful batch of neighbouring youngsters celebrating a holiday. “In fact, in the morning the water was up to the hip level. I could not afford to take time off work and waited till noon for the water to recede. Finally, I sat pillion on my husband’s bike with my legs in a horizontal position to avoid getting splashed,” said Ms. Pavitra.

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