While there are a host of manmade and natural factors behind the increasing incidence of floods in Indian cities, it is the former that is more to blame, experts have warned, emphasising that the environment must be respected and things set right before it is too late.
Unplanned construction in low-lying areas and wetlands, rampant concretisation, choked and overwhelmed storm-water drains, as well as disappearing water bodies and natural water channels are responsible for urban floods, which throw life out of gear in cities every monsoon.
A spurt in spells of very heavy rainfall in short durations triggered by erratic weather patterns is a double whammy for already-choked urban infrastructure, which is unable to withstand the sudden pressure, experts say.
A well-thought-out urban plan that takes into account changing weather patterns, and strict implementation of existing building laws and guidelines and environmental rules, is what Indian cities desperately need to become flood-resilient.
“We live in a manner that does not respect the environment, individuals, or the species who share the planet with us,” said Dr Surajit Chakravarty, associate professor, School of Public Policy, Indian Institute of Technology (IIT) Delhi.
Chakravarty, who spoke in his individual capacity, said that the problem of urban flooding has been studied, and rules have been framed for setbacks, flood zones, and construction standards. But, he laments, they are not observed.
"Moving forward, we should respect the floodplains and water channels, and follow regulations,” he said. Flooding due to changes in weather patterns presents an emergent challenge. Planning for resilient infrastructure coupled with mitigation interventions will be needed, particularly in coastal areas, Chakravarty said.
Urban decay: The main cause
Images of flooded IT hub Bengaluru, which went under water in September, are still fresh in our minds. This entire monsoon season, many towns and cities across the length and breadth of India — Jodhpur, Patna, Guwahati, Silchar, Surat, Ahmedabad, Mumbai and Gurugram, to name a few — were flooded after spells of intense rain that overwhelmed their poor and choked urban infrastructure.
Urban floods are, however, not a new phenomenon. Some of the worst urban floods listed by the National Disaster Management Authority (NDMA) and National Institute of Urban Affairs (NIUA) include Bengaluru (2005, 2009, 2013) Hyderabad (2000, 2001,2002, 2006, 2008), Ahmedabad (2001), Delhi (2002, 2003), Chennai (2004, 2015), Mumbai (2005, 2007, 2015), Surat (2006, 2013), Kolkata (2007), Jamshedpur (2008), Guwahati (2010, 2011), Delhi (2002, 2003, 2009, 2010, 2013, 2016), Srinagar (1992, 2014, 2015), Jamshedpur (2008), and Kolkata (2007, 2013).
On the recent Bengaluru floods, T.V. Ramachandra, scientific officer at the Indian Institute of Science (IISc) — Bangalore, said frequent flooding in the city since 2000, even during normal rainfall, is a consequence of an increase in impervious areas, high-density urban development in catchment areas, and a decline in wetlands and vegetation.
The flooding is exacerbated by narrowing and concretised storm-water drains, choked drainage systems and sewer pipes, construction in the path of natural waterways, dumping of debris and solid waste, loss of interconnectivity between lakes, etc., Ramachandra said.
A National Institute of Urban Affairs (NIUA) factsheet also points out that urban floods are a result of inadequate or poor maintenance of storm-water drains, improper planning, encroachment of drains and water bodies, occupation of low-lying areas, modification of catchment areas, and climate change.
Lubaina Rangwala of WRI-India agrees, saying large establishments — both formal and informal — have been built on natural landscapes such as wetlands, lakes and riverine landscapes.
“Formal establishments such as the BKC (Bandra-Kurla Complex in Mumbai) or the IT hub in East Bengaluru are bigger contributors to the crisis, squarely because of the extent of concretisation. But informal settlements are at a greater risk of losses and damage,” said Rangwala, program head, urban development and resilience, WRI-India.
Just as in Bengaluru, encroachments and dumping of waste along the Mithi River in Mumbai or choking of natural water channels such as the Bharalu and Banhini and wetlands such as Silkaso Beel and Deepor Beel in Guwahati or the shrinking water bodies of Gurugram make these cities prone to flooding each time it rains heavily.
Halfway round the world, in Australia, environmentalists raised serious concerns over a spurt in construction in low-lying areas and floodplains to meet housing demand, when large swathes of the city went under water after unprecedented rain.
According to Kapil Gupta of IIT-Bombay, all Indian cities — be they coastal, inland, hilly, riverine or those near dams and reservoirs — are now vulnerable to flooding.
“Most of them have reached saturation point in terms of population growth and accommodation and thus, developmental activities have shifted to low-lying areas and near riverbanks,” Gupta, professor, department of civil engineering, said in an email response.
Bigger drains to match intense rainfall
The NIUA factsheet lists remedial measures that include planned and proper construction of a drainage network; regular maintenance of stormwater drains; use of porous construction material for pavements; water-sensitive infrastructure; a drainage basin as a base for city master plans; protection of lakes and water bodies from encroachments, etc.
Vishwanath S, a Bengaluru-based urban planner and civil engineer, stressed on the need to audit all stormwater drains to have a relook at their capacity in the wake of the increased spells of intense rainfall because of climate change.
“Bengaluru was ready for 60 mm but now has to be ready for 180 mm of rain. We have to relook at flood-prone areas and seriously rethink our strategy and be prepared for very heavy rain,” Vishwanath, a visiting faculty member at Bengaluru’s Azim Premji University, told this writer.
Bengaluru had received 99 mm of rain in 24 hours on September 6, 2022, and 131.6 mm of rainfall a day earlier, its wettest day since 2014, reports said. When Mumbai drowned in 2005, it received 944 mm rain in 24 hours, a 100-year high.
According to Vishwanath, the authorities need to redesign stormwater drains and develop a new master plan for emerging areas to make them future-ready. “Plans for riverside or coastal cities, however, would be different from internal cities.”
Solutions may differ depending on the topography of a place but certain rules apply to all cities, Ramachandra said, stressing the need to protect and restore lakes and wetlands from encroachments and prevent narrowing and concretisation of stormwater drains.
Speaking specifically on Bengaluru, Ramachandra suggested the need to restore interconnectivity among lakes by removing all blockades, protecting valley zones and buffer regions, decongesting the city by shifting major installations to other places in Karnataka and stopping issue of no-objection certificates to major building projects.
The Intergovernmental Panel on Climate Change (IPCC) has warned that there could be an increase in instances of heavy rainfall in shorter spans of time in future, Gupta said.
This means that our existing drainage systems have to be redesigned to accommodate the increased flow levels, Gupta said. “This can be done either by resizing the drains or by judiciously integrating the best management practices into the drainage infrastructure.”
The NIUA factsheet also warns that with climate change, urban floods are expected to become more frequent, particularly in tropical regions, as the flooding season is likely to get longer and affect newer areas.
Build sponge cities
The experts pointed to the concept of sponge cities or green solutions that help the absorption or percolation of rainwater into the ground as a means to combat waterlogging.
Globally, the 'sponge city' concept is gaining much attention and uptake, Rangwala explained. China has a national mandate for all cities to incorporate 'sponge elements' in design and planning.
“These are basically landscape design elements that allow percolation of water, and create natural drainage and micro-climates to manage heat island effects. These, of course, have immense co-benefits on biodiversity, public health and quality of life,” she said.
Rangwala, however, warned that these elements would not work in isolation, especially in heavily concretised cities such as Mumbai. One has to take on a systematic approach to integrate such elements and city departments need to start managing these as part of their city infrastructure, she said.
Vishwanath and Ramachandra also spoke on the need to integrate floodplains with water bodies to help create sponges that can absorb rainwater to a great extent and to get citizens involved in building rainwater harvesting systems.
Riparian vegetation in the floodplains and drains helps in the retention of water. Porous landscapes allow the infiltration of flood water. Lakes can be rejuvenated to enhance water storage capacity and facilitate groundwater recharge. Mini forests of native species can also enhance the recharge potential, Ramachandra said.
Ramachandra said there has been a 1,055 percent increase in paved surfaces in Bengaluru in the past five decades. The implications on natural resources are huge: There has been an 88 percent decline in vegetation cover, a 79 percent decline in water bodies and an increase in the mercury levels (~2 to 2.5 ºC) in the last decade.
“We need appropriate strategies to make the city liveable and we need to stop this senseless unplanned urbanisation immediately.
Mapping floods, better rain forecasting
Mapping rainfall and flood data will help the authorities gauge under what conditions a city is likely to face problems and design solutions accordingly, the experts said, and stressed on improving weather prediction systems to warn people ahead of any such eventuality.
Asked if we could take a cue from local tribal communities in Assam, where houses are built on stilts in flood-prone areas, Rangwala suggested that at a local scale, households are already rebuilding their homes to manage existing flood levels. What may or will have to change is coordinated efforts and better information, she said.
If a city publishes its flood maps, with estimated water levels and projections based on rainfall trends, people can make calculated decisions, she explained.
A catchment can be planned based on its terrain and flows to suggest redevelopment guidelines in high-end neighbourhoods to ensure flood resilience once buildings are rebuilt, Rangwala said. “Incorporating risk information in planning is critical.”
Vishwanath said cities can look at stilt-parking as basement parking is a bad idea as seen in most flood-prone areas.
Gupta of IIT-Bombay explained how with the advanced instrumentation, technology and information, it is quite easy to forecast an urban flood and issue early warnings.
The Municipal Corporation of Greater Mumbai, Gupta said, has installed 60 automatic weather stations to record rainfall every 15 minutes. This information is disseminated through the disaster management authority web portal in real-time during the monsoon.
Vishwanath also mooted the setting up of automatic weather stations to issue accurate three-day forecasts to caution people in the event of sudden and very heavy rain.
Rangwala said this is a critical time for the government to take climate risks into account in urbanisation schemes, policies and programmes. If there is a Smart City 2.0, it is imperative that it puts environmental and climate actions front and centre.
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