With each passing year, Chennai residents are increasingly concerned about the unbearable summer followed by large-scale flooding. Experts attribute the rising temperature and flooding to rapid urbanisation that reduce the green cover and the spread of waterbodies. To mitigate the impact of heat wave and flooding, experts have recommended improved land use planning, better maintenance of waterbodies, and more effective solid waste management strategies.
At the recent Tamil Nadu Climate Summit 3.0, former IAS officer V. Thiruppugazh, the head of the Advisory Committee on Mitigation and Management of Flood Risk in the Chennai Metropolitan Area, said Chennai was projected to experience a temperature increase of 1.9 degrees Celsius by 2040 and 2.9 degrees Celsius by 2080, compared with the baseline level.
59% increase
According to the data provided in a report, ‘Beating the Heat: Tamil Nadu Heat Mitigation Strategy’, between 2003 and 2023, areas having temperatures of 24 degrees Celsius-26 degrees Celsius increased by 59%. The Urban Heat Island effect in Chennai and Tiruvallur has increased by nearly 3 degrees Celsius, says the report. Projections indicate that by 2050, the average maximum temperature in Tamil Nadu is likely to rise by 0.4 degree Celsius, with northern districts likely to experience more heat. Heat wave in Chennai is projected to increase from 42 days during 1985-2014 to 81 days during 2021-2050, the report cautions. Many nights are warmer in the city’s urban areas than in periurban areas, and an increase in the built-up area is cited as a possible reason.
In his lecture on ‘Addressing Heat Wave Risks in a Warming World: Integrating Climate Adaptation Strategies’ at the summit, Mr. Thiruppugazh proposed expanding access to drinking water, adjusting official working hours, creating cooling shelters for outdoor workers, planting more trees, and installing cool roofs to tackle the rising temperatures.
A former Chief Planner of the Chennai Metropolitan Development Authority (CMDA) points out that intensity of rain is high but it is of a short duration. “Tamil Nadu is a water-deficit State and it cannot afford to let water drain in the sea. The land available in the flood-prone locations must be identified and used for farming or creating parks rather than houses. These areas can act as water storage, and property damage from flooding can be reduced,” he says.
‘Fortify the property’
“If permanent development is unavoidable, property must be fortified with tall compound walls and larger storm water drains and pumping systems. Further, the Madras High Court’s order to the government departments that 10 saplings be planted for every tree cut should be extended to all private establishments,” he says.
‘Approach Paper to Chennai Climate Action Plan’, published by Habitat Forum INHAF, an NGO engaged in human settlements development, points to shrinking wetlands. It proposes a substantial increase of the green cover in the Chennai Metropolitan Area, from 6-12% to 25%. The report also suggested relocating the Coastal Regulation Zone (CRZ) inland by approximately 500 metres to prevent the construction of new residential and commercial buildings and abandoning the plan to increase biofuel dosing in petrol and diesel.
‘Bio-methanation is better’
D. Raghunandan, Climate Lead for the ClimACT-Chennai programme of INHAF and lead author of the paper, suggests bio-methanation instead of waste-to-energy plants, which are causing air pollution from incineration of waste. “Bio-methanation involves organic materials microbiologically converted under anaerobic conditions into biogas, which is cleaner. The only requirement for the process to work efficiently is that the wet waste should be devoid of plastic. In Indore, decomposting is done, but that is space-consuming and there are not many consumers for the product, like farmers.”
He also points out that concrete stores more heat, thus increasing the need for air-conditioning. If energy-efficient materials are more widely used, the cost of green buildings will decrease. These energy-efficient materials help in natural cooling, reducing the use of air-conditioning, he says. “Also, the State Energy Conservation Mission’s recommendation for people to set the temperature of their air-conditioners at 26 degrees Celsius must be made mandatory, especially for commercial and transport services,” he adds.
Shrinking wetlands
The paper also says the Pallikaranai marsh, once spread over 50 square kilometres, shrank to 5.99 square kilometres by 2007. It now covers a mere 3.17 square kilometres. Coastal wetlands in Kovalam have diminished owing to urban encroachment. It says the Kosasthalaiyar, one of Chennai’s three major rivers, has suffered severe degradation. Industrial expansion has reduced its 8,000-acre catchment by at least 1,500 acres. Sludge and the absence of dredging have decreased its depth from an estimated 14 feet a century ago to around two feet. This has lowered its capacity to absorb floodwaters and moderate local temperatures through evapotranspiration.
The report recommends restoring the wetlands, creating new waterbodies, rejuvenation of rivers, and removal of industrial encroachments, and stricter conservation measures to improve flood management and groundwater recharge.
S. Janakarajan, president, South Asia Consortium for Interdisciplinary Water Resources Studies, says, “In the context of climate action and climate resilience, what is the most needed for Chennai is to work towards preparing water security strategies which can contribute to flood and climate resilience.” He says that besides the three major watercourses (the Buckingham Canal, the Adyar and the Cooum), the major basins of Kosasthalaiyar and Kovalam, 18 macro-drains and 33 micro-drains have been under-maintained, and the interaction of outer and inner ring roads over small streams obstructs natural water flow to the canals, leading to more flooding.
Greater Chennai Corporation Commissioner J. Kumaragurubaran says the government has asked for information on heat-related studies to formulate a new heat wave mitigation plan.
Published – February 23, 2025 11:11 pm IST