Two Years Since Chennai Floods, a Forecast System Is on Its Way

IIT Madras, IIT Bombay and Anna University are developing a flood forecast system to predict floods.

Critical patients on stretchers being rowed down in boats; good samaritans wading through neck-deep waters to save trapped animals; looking up at the sky and hoping for a helicopter to drop a few packets of food... such images of the 2015 Chennai floods are still fresh in the minds of people.

Nobody wants to even risk the chance of a repeat episode. So a group of scientists from IIT Madras, IIT Bombay and Anna University are developing a flood forecast system by which you would be able to issue a flood warning well in advance.

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The Principal Scientific Advisor to the Government of India had pitched the idea to devise a system to forecast floods, and after 2015 the study area was decided as Chennai and neighbouring suburbs.

The institutions were roped in with the help of the Ministry of Health and Family Welfare, State Public Works Department, Chennai City Corporation, India Meteorological Department and other central agencies.

So How Does It Work?

First, in order to measure the amount of precipitation over a set period of time, it is necessary to install rain gauges which double up as automatic weather stations. They have been installed at 15 places in and around Chennai, like Arakkonam, Kaveripakkam, Vandalur and Poonamallee, which have good GSM network and security. These gauges collect all weather parameters such as temperature, wind speed, relative humidity, to help study the extent of rainfall better.

Second, to evaluate the type of soil in every riverine area and how it reacts to rainfall. For example, the Adyar area has clayey soil, while Couum and Kosathalaityar is sandy.

Third, water level loggers or sensors have been placed in over 15 locations such as Okkiyam, Pallikaranai, Adyar, Couum, and Kosathalaiyar. These essentially measure the level of water flowing in the nearby reservoir.

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So Can We Prevent Floods?

Prevent?  No. Predict and take precautions? YES.

With the rain forecast provided by the IMD and the data the team collects through the system installed, IIT Madras vouches that once the system is in place completely, they can warn at least 72 hours before a flood hits the city.

The information will be shared with the State Disaster Mitigation agency and agencies can be alerted for people to be evacuated.

We want at least version one operational and running by southwest monsoon 2018 starts next July. The summer showers won’t cause any flooding, but we will have something to test out and fine tune our model. But yes, we can predict floods!

Balaji Narasimhan, Associate Professor, Department of Civil Engineering, IIT Madras

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So Could we Have Averted the 2015 Disaster?

Well, Professor Balaji says a resounding no. The intensity of the rains were such that the floods would anyway have struck the city. But what could’ve been done to minimise the damage was to spruce up the archaic British laid sewage and water management system and put in a little more thought into urban planning.

Also, when weather forecaster Ramanan says you can expect moderate or heavy rainfall, there is no system to translate that into a forecast for flood alert.

Balaji Narasimhan

The IIT Madras professor also dismissed the misconception that opening the gates of the Chembrambakkam lake had played havoc during the floods.

If you think Chembrambakkam had released 29,000 cubic feet per second at the maximum, three times that amount of water came from Tambaram, Mudichur and others due to the breaches in the tanks. Meanwhile, our estimate is that 1.3 lakh cusecs passed through Adyar. So if you compare, you will realise even without Chembrambakkam water release, we would’ve been flooded anyway.

Balaji Narasimhan

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Flood and Drought Are Two Sides of the Same Coin

Tamil Nadu, a state which is largely dependant on agriculture, has been affected year-after-year by the droughts. Crops have failed, farmers have committed suicide and there is always a long queue of buckets and pots near the water lorries and tanks. We are largely dependant on 2 months of rains, for 10 months of water needs.

Professor Balaji claims that if you look at the aerial images of the flooded zones, you can retrace the extent of water bodies that were there initially, before man built his concrete jungles.

If you take care of water bodies, they will recharge the bodies and you will be able to tide over the drought season.

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So is the State Doing Enough to Prepare for Floods?

Well, this year too, even after a short spell of rains roads were inundated and streets waterlogged. The civic body has still not levelled and desilted all roads so that water can percolate more easily and encroachments checked and cleared.

But sources say they have learnt their lesson.

The Tamil Nadu Urban Infrastructure Financial Services is working on a flood forecast system on a much larger scale, with hundreds of sensors spread out in vital areas in and around the city.

Hopefully, there won’t be another 2015-like episode. And even if such a disaster strikes, at least all Chennaiites will be on some higher ground watching all the action and not be washed away in it.