Large swathes of Bangalore in India are now submerged following exceptionally heavy monsoon rains. Experts say the floods have been exacerbated by poor urban planning, highlighting how cities in India and elsewhere need to adapt as climate change brings more extreme rainfall in the future.
This week, boats and tractors could be seen carrying commuters to work on the waterlogged roads of the Karnataka state capital, while hundreds of families had to be evacuated. More than 120 of the city鈥檚 210 artificial lakes have overflowed this month, fuelled by precipitation in the southern part of the state.
The unprecedented rains didn鈥檛 come as a surprise to climate scientists. In its latest report, the Intergovernmental Panel on Climate Change across South Asia. In the next decade, India鈥檚 southern states are likely to see an increase in high-intensity and very high-intensity rainfall events, with precipitation of more than 100 millimetres per day, according to at the Center for Study of Science, Technology and Policy, a Bangalore-based think tank.
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Earlier this year, Murthy co-authored a study describing at a district level. She found that under a scenario of moderate global carbon emissions, southern India could experience up to two additional very high-intensity rainfall events per year, and up to three under a high-emissions scenario.
Bangalore, an IT hub, has 99 automatic weather stations that have been collecting data for the past 10 years, says , a civil engineer and water expert who helped design water management policies in the city. 鈥淭he results confirm that rainfall intensity is going up, but also that rainfall patterns vary across the city,鈥� he says. This is because its expansion has contributed to the urban heat island effect in which cities retain more heat, altering the local microclimate and in turn the strategies needed to manage it.
鈥淏angalore wallows in nostalgia 鈥� we talk of our old water systems and we believe if they were protected that alone would prevent flooding,鈥� says Srikantaiah, but the existing system was designed to trap water for irrigation. For example, Bangalore鈥檚 lakes aren鈥檛 equipped with sluice gates, which means they can鈥檛 release excess water and their water level cannot be lowered in anticipation of rain.
鈥淲e now have to invest in infrastructure appropriate for these very intense rains, such as improved sewerage, stormwater drainage and solid waste management,鈥� he says. This would ensure debris isn鈥檛 washed away by floodwater, clogging drains.
As well as safely removing excess stormwater, urban planners envisage a 鈥渟ponge city鈥� able to store it for when drought comes. 鈥淭he climate crisis also means that this year we could have too much rain, and next year too little,鈥� says Srikantaiah.
With the non-profit organisation Biome Environmental Trust, he is leading a drive to build 1 million wells across the city, to harvest rainwater and recharge the aquifers with the equivalent of about 1500 million litres per day during the wet season. Around 200,000 wells have already been built, he says.
Cities around the world must plan for different types of climate hazards, including heatwaves and droughts, at the same time, says at the University of Reading in the UK. 鈥淲e can鈥檛 assume that what we鈥檝e seen in the last 20 years in our cities will stay the same,鈥� she says.
This is particularly hard at a time when the world is facing a financial and energy crisis, she says. 鈥淏ut in the long term, unless we do those types of things, deaths will happen.鈥�
Bangalore鈥檚 well-digging initiative is a step in this direction, but a radical overhaul of urban infrastructure is unattainable for many cities, particularly in low-income countries. In these places, Cloke says, 鈥渢he low hanging fruit are early-warning systems: being able to tell people that something is going to happen, and for the authorities in charge to evacuate people when needed.鈥� These systems are cheap compared with other options, she says. 鈥淵ou can just begin immediately and all you need is one person in a room.鈥�
