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Shower & shape inflict pain
5 reasons for cup of seasonal woes

Heavy shower, saucer shape and clogged drains left several pockets in the eastern part of the city water-locked for almost a week.

While thousands of residents had hard times because of the weeklong waterlogging conditions, the bureaucrats, politicians and even the chief minister indulged in exchange of verbal volleys on the issue. Patna Municipal Corporation (PMC) was at the receiving end most of the time.

Chief minister Jitan Ram Manjhi called it a failure of PMC. Senior leaders in the BJP, including Leader of the Opposition Nand Kishore Yadav and former deputy chief minister Sushil Kumar Modi claimed that the chief minister was making PMC a scapegoat to hide the failure of his government.

The Telegraph probes the reasons behind the flooding:

Rain rush

The waterlogging in most parts of the city started with record rainfall of 210mm in just nine hours on August 14 — breaking the earlier record of 205mm rainfall on August 30, 1997. The downpour continued on August 15 when the city received 102mm rainfall, followed by 65mm on August 16.

Faulty flushout

The civic body does not have any estimate with regard to capacity of rainwater drainage nor is there any separate storm water drainage network in the city. However, technical experts in the PMC said it could drain out water from the streets in 24 hours if it rains up to 65mm between 10pm and 2am. However, it would take around 48 hours to drain out the same amount of water if it rains between 2am and 10am. It takes more than 48 hours if it rains above 65mm in a day.

“If PMC takes more than 48 hours to discharge water from the city if it rains more than 65mm in a day, then it is not difficult to understand why it took seven days to flush out 372mm of continuous rain in 72 hours,” said R.S. Choudhary, a retired town planner.

Saucer setback

According to Patna city development plan prepared in 2006, under the centrally sponsored Jawaharlal Nehru Urban Renewal Mission (JNNURM), the topography of the city is saucer shaped posing difficulty in flushing out the water. This gets aggravated by the fact that the Howrah-New Delhi railway line divides the city into two halves, causing additional inundation. The city receives about 1,100mm of monsoon rain every year and flooding in the city is annual. The southern portion of the city remains waterlogged for most times of the year.

“Accumulation of rainwater is inevitable for Patna as it is a saucer-shaped city. On top of that, the development of the city over the past two decades has been done in an unregulated manner,” said Ashok Ghosh, the professor-in-charge of the department of environment and water management at AN College.

Primitive drainage

The entire drainage system of the city is based on small and big drains built more than 50 years ago during the British rule. As a result, they do not have the required capacity to hold and drain out the excess rainwater. The JNNURM city development plan states that the existing storm water drainage system is limited to certain areas and over the years heavy siltation has taken place, chocking the existing drains.

The JNNURM report states that 52 per cent of the drainage network of the city falls in four neighbouring municipal bodies.

Drain doldrums

One of the most important reasons behind waterlogging in Rajendra Nagar was found to be reverse flow of excess water from the upstream of Saidpur Nalah near Bazaar Samiti.

This was primarily because of clogging of the nalah by dumping of waste material and encroachment of drains by constructing houses over them.

At times, it can take even 500 to 1,000 years for plastic bags to decompose. The waste material at times leads to breakdown of the sump houses as well.