Urban Flooding: Learning from Chennai's Past to Build Resilient Cities

Entering December, as disaster experts of the country are anticipating and preparing for expected cold waves due in January in many states, the landfall of cyclone Fengal in Tamil Nadu takes us back to the days of July and August 2024, when several cities across India were struggling to ‘stay afloat’ amidst extreme rainfall and consequent urban flooding. It was only as recently as October 2024 that Chennai experienced flooding and was again flooded at the end of November. It is interesting to note that every spell of rainfall now can cause waterlogging and urban flooding in this important city. All sectors working on research, implementation, and financial feasibility for risk reduction and resilience must, therefore, align forces to find solutions to these urban floods occurring now, not every year, but every quarter.

While urban flooding may not receive the same gravitas as riverine flooding, flash flooding, or glacial lake outburst flooding (GLOF), it has continuously been recorded since the past decade to cause loss of life, livelihoods, severe infrastructure damages, and disruption to the economy for days on end. Critical infrastructure, including healthcare, has not only ceased functioning but also collapsed (structurally, operationally, or both) during urban floods.

As Chennai battles with urban flooding yet again, it may be worthwhile to look back at the ghost of deluges past while the cyclone and heavy rainfall passes us by. Chennai has experienced notable urban floods in 1976, 1985, 1996, 1998, 2005, 2008, 2010, 2015, and 2023. The 2015 urban flood of Chennai was an unmitigated calamity that was unexpectedly devastating. The deluge caused by the opening of the Chembarambakkam reservoir during very heavy rainfall without prior adequate warning led to emergency evacuations for people living near the banks of the Adyar River and other low-lying areas. Unplanned development, illegal construction, and lack of environmental impact assessments significantly contributed to the flooding. These are common phenomena observed across all Indian cities struggling with urban floods.

Lower floors of hospitals were inundated, patients shifted to upper floors, backup supplies were exhausted due to disruption in the supply chain, shortage of food and water supply, power losses in huge parts of the city disrupted operations of the IT sector, all modes of transportation suspended, livestock and poultry died, and agricultural lands were destroyed. With water levels increasing up to 10-12 feet, 1 lakh houses were damaged, an estimated economic loss worth 20,000 crores incurred and more than 200 people lost their lives.

Similar losses have also been recorded during the previous urban floods in Chennai. While rapid and unplanned urbanization is typically held accountable for increasing urban flooding occurrences, the older and more obsolete drainage designs are also to be blamed. The Central Public Health and Environmental Engineering Organization (CPHEEO) published a ‘Manual on Sewerage,’ with guidelines for designing drainage systems using a uniform design rainfall intensity of 12-20 mm/hour for Chennai, Mumbai, and Delhi. With rainfall recorded at 50-70 mm/hour this decade, drainage systems are not only obsolete but also largely failing.

At SEEDS, we work to provide relief and response post-disaster. Still, our higher goal has always been to enhance preparedness and awareness in the communities, to help them prepare, adapt, and become more resilient. Post the 2015 floods, in addition to the distribution of utilities and hygiene kits, interventions such as designing and constructing safe transitional homes for 200 families, distribution of non-electricity water purifiers, repairs to a school, setting up WASH committees, and conducting hygiene awareness activities. It was observed that the majority of the low-lying areas get inundated for days together, and the low-income households in marginalized communities continue to stay in waterlogged houses. Rebuilding their homes and enhancing their flood preservation skills were both essential. Increasing community reliance through women-led WASH committees notably changed the residents’ perspectives towards their vulnerability.

With urban areas still operating on half-a-century-old drainage systems and rapidly urbanized areas quickly losing their infiltration capacities, the vulnerability of the city and its residents only increases. It is rather dreadful to consider every warning of rainfall or cyclone as a premonition of an urban flood. Impacts are not limited to damage and disruption; loss of lives has escalated over the past decades. It may be helpful to acknowledge that the availability of post-flood relief for the community does not diminish the gravity of the impact of unplanned development in old and new cities. Learning from the ghost of past deluges and enhancing the resilience and preparedness of communities and infrastructure would be a fitting redemption. Cities may be ‘smart,’ ‘sustainable,’ or ‘green,’ but until they are resilient, the ghosts of urban flooding will haunt us.

This article is authored by Sumedha Dua, a project manager at the Sustainable Environment and Ecological Development Society (SEEDS)

(No Hans India Journalist was involved in creation of this content)