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In the last few years, the intensity and frequency of floods have increased, leading to many of the city’s streets getting inundated even after short spells of rain.
Just like there are several reasons for the occurrence of floods, it is important to talk about solutions to mitigate such extreme weather events.
Some things that could be taken into account to do so includes:
In Chennai, some areas flood more than others in a much faster time span. This is determined by the area’s location – whether it is built on a water body or high ground. Identifying the past of the area and comparing it with the present will help us take appropriate measures. The vulnerable areas might need a flood tunnel to take the excess water away, deeper and larger stormwater drains, etc.
Three teenagers decided to take matters into their own hands and started mapping the lost lakes in Chennai in hopes of helping to solve the water scarcity and the flooding. With the help of a group called Ulagalaviya Ilanthamizhar Kuzhu, they formed three teams – one team identifies the lost lakes from old maps, the second team verifies them with old books and archives, the third team talks to the people on the ground to talk about the flooding in their area.
Nandabhalan, one of the members believes that since the water still follows its old stream, the government would be able to identify where the stream is blocked through their map.
They released a map called “மெட்ராஸ் இழந்தது ஏரிகள்”, which translates to Madras’ Lost Lakes with the description “இயற்கையை நாம் அழித்தால், அது நம்மை அழித்துவிடும்!!!”, translating to If we destroy nature, it will destroy us. Of the 97 lakes they’ve mapped, at least 32 have vanished entirely and the rest are rapidly shrinking. These lakes appear as a blue sheath over the present-day urbanized Chennai.
Here is a picture from the map of the Adyar river over present-day Chennai. The map from the year 1814 shows that this was an island.
Stormwater drains are essential as they prevent flooding by draining the excess water away. However, the low number provides very little coverage considering the number of vulnerable areas. Apart from that, even areas with SWDs still show quick and intense flooding which naturally makes us question the quality of the SWD.
In an RTI reply from October 2018, Satta Panchayat Iyakkam (SPI), an NGO found out that there was only 1894 km of SWDs against the city’s road stretch of about 5500 km, which means only 34% of the roads in Chennai are capable of draining water.
As of January 2021, the SWDs coverage increased to 2,071 km, which is less than 50%. This means half of Chennai has no stormwater drains. It was revealed from a study by the Greater Chennai Corporation (GCC) in January 2021 that about 45 km of SWDs are missing in the city.
A Corporate Engineer to The Times of India explained that for the 15 lakh houses in Chennai, only 8 lakh of them have sewages, which means the houses lacking them let the sewage in the stormwater drains.
This clearly means that more sewages and stormwater drains are required to adequately drain the excess water and prevent flooding. Even the SWDs already present are not doing their job because of the lack of study beforehand.
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Quantity alone can’t help flooding in the city because there’s frequent and quick flooding in areas with SWDs.
Before the construction of SWDs in areas, a contour study must be conducted. It is a key preliminary process. Dayanand Krishnan, civil engineering expert and Geographic Information System (GIS) consultant explained to The News Minute that a contour study marks equal points of height in a map, and the SWDs must be built using them such that the water flows from a high gradient to a low gradient, and then naturally into the nearby water bodies.
This would be of large help to the civic body to plan the SWDs without flaws.
However, the current SWDs in the city show a lack of understanding about the area. Ashok Nagar and T Nagar are often cited as examples of poor planning in the construction of SWDs. Lack of linkages, gradient flaws, inadequate size of SWDs, and reverse flows was observed in these areas.
Before the construction of SWDs, there must be proper contour and rainfall catchment studies to understand how the SWDs must be built. It’s crucial to connect the SWDs to a natural water body nearby. If there is an absence of a nearby water body, artificial canals must be built to ensure the water traverses smoothly. Subject matter experts must be called on for opinions before building the SWDs to avoid any flaws.
Under the Greater Chennai Corporation (GCC), the build-up area has increased from 47 sq km in 1980 to 402 sq km in 2012. The increasing developmental projects and rampant urbanization reduced the wetlands from 186 sq km to 70 sq km. There has been some amount of pressure in recent times urging the government to take action.
Jayaram Venkateshan of Arapor Iyyakam said despite the judiciary ruling that it is illegal to reclassify water bodies, it is still being done continuously. The Madras high court two years ago asked for a comprehensive list of the encroachments across the state. However, the state government is still yet to submit the list. The court summoned the chief secretary because of the delay.
During the November 2021 spots of rain, the Madras high court threatened the Greater Chennai Corporation (GCC) with a suo moto public interest litigation if the waterlogging did not improve.
The Tamil Nadu government set up a Special Purpose Vehicle (SPV) – Tamil Nadu Green Climate Company to manage three critical missions. One of them is the Tamil Nadu Wetlands Mission, where they aim to map 100 wetlands in 5 years to restore the ecological balance.
Following this mission, the TN government proposed to declare the Pallikaranai marshland in Chennai a Ramsar site. The Pallikaranai marshland shrunk by 12000 acres in around 48 years. Making this a Ramsar site essentially means this would become a wetland of international significance, enabling conservation and wiser use of wetlands.
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The Indian Institute of Technology (IIT) conducted a modelling study and found out correlations between the increasing carbon emissions and extreme rainfall. IPCC (Intergovernmental Panel on Climate Change) in their report called Changes in Climate Extremes and their Impacts on the Natural Physical Environment noted the climate change “has detectably influenced” several factors that contribute to floods like intense rainfalls, heavier precipitation, increasing sea levels.
NASA based on IPCC’s reports claimed that Chennai is one of the 12 coastal Indian cities that’s likely to be submerged by the end of this century. Tamil Nadu governor R.N Ravi in an annual convocation speech acknowledging climate change, asked students and researchers to prepare for the uncertain consequences of climate change. He cited the changing monsoon patterns, rising sea levels, heatwaves, intense storms, cyclones, and flash floods.
Avilash Roul, the principal scientist at the Indo-German Centre for Sustainability, IIT-Madras wrote about the dire need for innovation in the ability to govern due to a multitude of risks arising from climate change.
The Tamil Nadu government proposed to set up the Chennai Metro Flood Management Committee (CMFMC) in the city. The committee would comprise experts in environment, urban planning, disaster management, devising flood control methods, and designing stormwater drains to reduce the devastating effect of flooding. The chief minister of Tamil Nadu M.K Stalin urged officials to make disaster management in the state a ‘people’s movement’. Roul called the proposed CMFMC long overdue.
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Addressing the different concerns ranging from the proper mapping of Chennai, better stormwater drains, better urban planning that reduces encroachment and preserves water bodies, to addressing and acknowledging climate change can help solve or at the very least reduce the intensity and mitigate the impacts of floods.