Chennai floods: What happened at Chembarambakkam, negligence or nature’s fury?

Here is a crystal clear explanation of what is going on.
Chennai floods: What happened at Chembarambakkam, negligence or nature’s fury?
Chennai floods: What happened at Chembarambakkam, negligence or nature’s fury?

Media reports stating that the delay in opening sluice gates at the Chembarambakkam Lake caused the heavy flooding in several parts of Chennai, which led to deaths, has set alarm bells ringing in the Public Works Department (PWD) of the Tamil Nadu government. On Wednesday morning, an urgent report was being prepared by officials of the PWD for briefing the Chief Minister.

Here is a crystal-clear explanation of what is going on.

First, we need to understand the Adyar River, Chembarambakkam Lake and how they are connected to Chennai’s flooding.

The Adyar River originates from a tank near Manimangalam village in Sriperumbadur in Kanchipuram district, but it is only when the water from the Chembarambakkam lake joins the river that the stream appears. The river then flows through Tiruvallur and Chennai and flows into the Bay of Bengal at Adyar in Chennai.

Chembaramkabbam Lake is a rain-fed reservoir which supplies water to Chennai city through pipelines. When the lake's water flows over capacity, the excess is released into the Adyar River. Releasing excess water into the river is important, because if that is not done, then the lake walls could breach, leading to an uncontrolled flow of water into the Adyar, and thus Chennai city.

The lake can hold water up to a maximum level of 24 feet (the measure which is used to indicate the amount of water), with a full capacity of 3645 million cubic feet (which is the volume of water it can hold).

During heavy rains, when the water level is close to full capacity, water is released into the river. The amount of the release of water is measured in “cusecs”, which is “cubic feet per second”.  The more “cusecs” of water is released into the Adyar River, the faster water will rise, eventually overflowing into the banks of the river.

When too much water is released in a short period, Adyar River overflows, flooding residential areas and other parts of Chennai. This is what is believed to have happened on December 1 and 2.

So, what are the allegations now?

Several reports have been published by media houses over the “negligence” of government officials in either not releasing water at the right time or in not giving out enough warning to people living in areas around the Adyar River so that they could shift to safety.

Going by the major reports in Times of India and The Wire, the following allegations have been levelled.

One, there was a bureaucratic delay in opening the sluice gates at the lake, because of which the flooding was excessive, when the gates were eventually opened.

Two, Adyar was carrying more than one lakh cusecs of water on December 2 and 3, much more than the official account.

Three, though some press releases were given out by the Chennai Collector regarding water levels, they did not convey the intensity of the water levels, especially later in the day on December 1.

The reports imply that officials in Chennai were lax in warning people about the rising water levels.

What is the PWD’s version and what happened at Chembarambakkam?

The News Minute has since spoken to top officials of the PWD to understand their side of the story. We have spoken to the Principal Secretary of the PWD and another engineer at the PWD who was at Chembarambakkam Lake on the fateful night.

NS Palaniappan (Principal Secretary) PWD says that the accusations are incorrect, “We opened Chembarambakkam flood gates as per regulation. We cannot do more than that,” he told TNM.

He also denies bureaucratic delay. “The regulation lies with the Chief Engineer and he regulated it. I know he did it judiciously. As the rain was heavy, beyond a limit they cannot hold it up. According to the flood manual, they can hold it up only to 2 metres.” He also says that warnings were given well in advance.

The engineer of PWD who TNM has spoken to, laid out what happened that night very clearly.

On that night, at least one Chief Engineer, one Senior Engineer and one Assistant Engineer were present at the lake apart from the regular staff. The senior officials had gone to the lake to monitor the situation between midnight on December 1 and 5am on December 2.

The engineer has given us data in an attempt to prove that water was released from the lake in a systematic manner.

On December 1, as the day progressed, the inflow of water into the lake increased due to the rains, and correspondingly the outflow of water from the lake to the Adyar River was increased.

According to the engineer, 6pm was the major breaking point when the water level reached dangerous levels. The engineer says that water was never released beyond 29,000 cusecs.

“We saved the reservoir, and we restricted the outflow to 29,000 cusecs so that too much water does not flow into the river. We were getting about 31000 cusecs of inflow till 6am in the morning, but we never crossed the limit,” says the engineer.

Then why was there such excessive flooding in areas in Chennai?

“There was 47.5cm rainfall which is unimaginable – we cannot stop nature. Adyar river has its own catchment, we cannot say that Adyar river increased only because of the Chembarambakkam lake, the rainfall was at 50cm in Tambaram – that is unpredictable rainfall – and all that comes to the Adyar river. So if there was excessive flooding, it need not be just because of Chembarambakkam,” says the engineer.

Did they give out enough warning?

“Every time we increased the level of release, we informed the district collectors, people at the revenue department, local Tahsildars, Village Administration Officers, the Chennai City Corportation, we have informed everyone,” he says.

Why did they not release enough water earlier?

“It is wrong to say that we should have released the water earlier, even if we had emptied the entire Chembarambakkam lake and kept it, the water would have filled up in just a day. The inflow was very high,” he says.

The engineer laments, “We have risked our lives to save others. Several engineers, we were at the spot and trying to do the best, and we are being blamed now.”

Interestingly however, the PWD Secretary had a slightly different version. When asked what would be done if something like this happens again, he says, “We are cautious now and we have reduced the levels sufficiently now. We have reduced it so much that it can hold even heavy rain.”

So why wasn’t that done earlier?

“We had reduced, but not heavily. Now, we have seen the kind of rain and have made provisions,” he says.

Several other questions remain unanswered.

After being informed by the PWD officials, did officials of Chennai Collectorate and City Corporation do enough? We have not been able to get through to the Chennai District Collector or the Commissioner of City Corporation. But even if conventional means like press releases to media houses were used to warn people, is that enough in the face of an unprecedented calamity?

Everyone would agree that this was a natural disaster of epic proportions and no government in India could have been prepared entirely. But the hydrological systems of the city are well known and understood. Further, in the days running up to December 1, there was a round of torrential rains which exposed the unpreparedness of the city. There were enough warnings on the rains by the Met department. Should the government not have prepared better?

The Tamil Nadu government has come under severe criticism for its lack of communication, and this time, it has cost lives. If allegations of bureaucratic delays due to lack of instructions from “the top” are true, then the loss of lives to flooding in Chennai perhaps typifies the flaws in the administration.

Related Stories

No stories found.
The News Minute