How incorporating lake sensors can prevent flooding during the Chennai monsoon

With Chitlapakkam Lake getting flow sensors that determine inflow and outflow of water into the lake, flood mitigation would become easier.

Every year, Chennai experiences severe flooding, with cars being washed away, homes submerged, and residents navigating waterlogged streets. One of the affected areas is Chitlapakkam, situated amidst three lakes — Chitlapakkam, Seliyur, and Rajakilpakkam — on Chengalpettu’s agricultural lands. Due to its proximity to these water bodies, Chitlapakkam suffers extensive flooding during Chennai’s intense monsoon.

We at Chitlapakkam Rising, along with the Water Resources Department (WRD) and Tambaram Corporation have worked on flood mitigation measures such as the construction of  ‘macro cut-and-cover drains’ around the lake, to drain out surplus water during floods.

We even initiated the construction of a flood regulator to regulate the flow of surplus water as it gets directed downstream and inundates our homes. All these drains are interconnected, carrying the floodwaters into Sembakkam Lake, located downstream. 

Read more: How Chitlapakkam remained flood-free during the recent Chennai rains 

However, using these drains effectively requires an understanding of their carrying capacities and real-time monitoring of surplus water flow during monsoons. This is why I proposed sensor systems and a lake control room, which tracks the water levels in the lakes.

Flow sensors help determine the net inflows and outflows of the lake and can send this information automatically with 24/7 backup and WiFi arrangement to the authorities at WRD and Disaster Management Command Centre. They can then take appropriate decisions to take pre-emptive measures to use flood regulators during the monsoon season. One such lake sensor is currently under construction at Chitlapakkam Lake.

What will lake sensors do?

The sensor will record the water level of the lake daily, which will help quantify the current water volume and storage capacity of the lake. According to the WRD, Chitlapakkam Lake has a storage capacity of seven million cubic feet. However, the water level in the lake fluctuates throughout the different seasons and even daily, making continuous sensor monitoring more than just a record-keeping measure.

So, what can we do with this information? If all inlets and outlets of the lake had flow measurement sensors, we could measure the amount of water that enters the lake and is discharged downstream. During monsoons, these sensors can notify authorities when the lake reaches its full capacity or exceeds the Maximum Water Level (MWL). This information can also be used to predict how long it will take to discharge the surplus water.

This approach can even help us assess how much rainwater is stored in the lake and how much is discharged into the downstream lakes. Based on capacity and surplus readings, we can deepen or revive urban lakes to store more rainwater and avert downstream flooding accordingly. This would facilitate better decision-making regarding existing flood mitigation drains and if more macro cut-and-cover drains were needed.

What happens in times of flooding?

lake sensor
The lake sensor facility being installed in Chitlapakkam Lake. Pic: Dayanand Krishnan.

During floods, when there is excess water, a lake control room would be quite beneficial. Once the lake gets filled up to Full Tank Level (FTL), the measurement equipment would automatically send alerts to the Disaster Management Integrated control room, where lake levels can be cross-checked.

The rainfall gauge sensors will provide information on the catchment area for Chitlapakkam Lake. If there is prediction of a certain amount of rain, the sensors can quickly identify how much water will be entering Chitlapakkam Lake, how much will flood the residential areas and how much water the lake will retain. This information allows flood regulators to open accordingly, serving as preventive measures to preempt flooding and control its extent.

Urbanisation and the need for quicker record-keeping

In recent years, there has been no monitoring of the inflow and outflow of rainwater into the lake, leading to a lack of real-time measurement records. Earlier, lakes were mostly situated in rural areas with large agricultural catchments. But, with rapid urbanisation, there is extensive construction in and around lakes, leading to severe flooding in the city.

Read more: Getting piped water supply to homes in Chitlapakkam

The discharge of rainwater has increased over the years, estimated to be at least three times higher. It is important to document these changes. By understanding the extent of this discharge, we can implement technologies like macro drains to manage specific volumes of floodwater, directing them to other lakes or deepening existing water bodies.

Sensors in Chennai: Where do we stand?

This project is the first of its kind in Chennai. The WRD has initiated a pilot project to install lake sensors in around 90 lakes, with construction currently ongoing at Chitlapakkam Lake. While constructing these sensors, we must ensure that lake control rooms and sensors have a proper power backup and internet support. As power outages are common in the monsoon, it is essential to have alternative power supply to avoid losing crucial data.  

It will also be important for the lake control room to work with field workers and disaster management command centre teams. Once the integrated control room and disaster management teams identify the level of water in the lake, as well as the inflow or outflow at each point in time, authorities can send field workers accordingly.

Once on the field, they can decide to open the shutters in situations of very heavy downpour with high surplus or flooding. Last year, when there was a lake breach in Medavakkam and a nearby Purvankara apartment got waterlogged, there was no flood regulator or any kind of surplus arrangement. The sudden breach caused the tank bund to burst, inundating around 200 to 300 cars. Such disasters should not happen in the future.

Ultimately, these sensors can help not only Chitlapakkam but anyone living near urban lakes in Chennai. In addition to this, rainfall should be seen as a valuable resource — one that can be redirected, harvested, and collected. In addition to lake sensors, residents should be advised to harvest rainwater rather than sending out all the water through stormwater drains.

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