Chennai rains: Can the city withstand another urban flood?

Seven years aft devastating floods killed much than 400 radical successful the confederate Indian metropolis of Chennai, the portion is witnessing terrible rains that are becoming harder to predict. BBC Tamil's K Subagunam finds retired if the metropolis is equipped to woody with the interaction of changing upwind patterns.

Schools and colleges person been unopen successful Chennai for the 2nd clip successful November aft dense rains lashed the metropolis connected Friday.

Videos showed radical wading done muddy waters which flooded the streets and residential areas of the coastal metropolis of 12 cardinal people.

Authorities are connected precocious alert arsenic much dense rains are expected successful the coming days.

The deluge comes conscionable 10 days aft the metropolis recorded its heaviest rainfall successful much than 30 years connected 1 November.

At slightest 26 radical person died successful rain-related incidents since 31 October.

Experts accidental the rains person not lone go much predominant but besides much unpredictable, making it hard for authorities to respond rapidly.

"No 1 could person predicted that the metropolis would person 140mm of rainfall successful 24 hours close astatine the onset of the monsoon play earlier this month," says Dr S Janakarajan, the president of South Asia Consortium for Interdisciplinary Water Resources Studies.

"It was an unexpected upwind lawsuit wherever forecasts changed from greeting to evening."

The authorities authorities tried to power the concern by bringing retired centrifugal pumps to wide waterlogged areas and sending its alleviation teams to flood-affected neighbourhoods.

But arsenic oversea levels emergence and vigor waves intensify, experts accidental the metropolis volition request to bash a batch much to mitigate the interaction of utmost upwind conditions successful the aboriginal and to debar a repetition of the deadly floods successful 2015.

"The information that h2o entered people's homes astatine the precise opening of the monsoon play shows conscionable however unprepared Chennai is this time," says SA Haris Sultan, a subordinate of anti-corruption watchdog Arappor Iyakkam based successful the city.

Located connected the seashore of Tamil Nadu state, Chennai is 1 of the largest cities successful India.

The metropolis is besides a hub for concern accumulation and automobile manufacturing.

Unlike a bulk of India - which depends connected southwest monsoon successful June for rains - the months of October and November are the superior monsoon play for Chennai.

The metropolis depends connected the rains to negociate its h2o needs during the summertime months.

In 2019, the metropolis witnessed a terrible drought and was forced to bring successful 10 cardinal litres of h2o per time from different districts to mitigate the crisis.

But geographically, Chennai lies connected a low-lying plain - with astir parts of the metropolis conscionable 2 to 5 metres supra oversea level.

In its latest report, the United Nations' Intergovernmental Panel connected Climate Change (IPCC) named Chennai arsenic 1 among 20 coastal cities successful the satellite that are expected to look large flood harm by 2050.

A pb writer of the study warned the metropolis would look a "double whammy of vigor and humidity, and cyclones" arsenic temperatures rapidly emergence successful South Asia.

To hole for the monsoon play this year, the section authorities carried retired an ambitious task to physique tempest h2o drains - which would cod excess rains from the streets and drain them into the sea.

But wrong 3 days of dense rains successful the archetypal week of November, the metropolis was wholly flooded, bringing beingness to a standstill.

Climate idiosyncratic Dr Roxy Mathew Koll says the metropolis faltered successful dealing with the concern due to the fact that of the progressively erratic quality of monsoons.

"We present person abbreviated episodes of beardown upwind bursts and dense rains which are little predictable and challenging to adjacent monitor, fto unsocial forecast," helium says.

Others experts accidental that the city's existent drainage strategy and groundwater structures are inadequate to halt wide waterlogging and to store rainwater for summers.

"Most of Chennai has go buildings and roads," says L Elango, a prof of geology astatine the city's Anna University.

Over the past decade, Chennai has witnessed large-scale operation and accelerated industrialisation - overmuch of which has grown without a program and with nary respect to h2o flows, and without anticipating utmost upwind events.

According to information from the State Planning Commission, much than 80% of onshore is nether operation successful the city.

Prof Elango says that gathering monolithic tempest h2o drains and groundwater recharge structures connection small benefit, arsenic Chennai's factual topography prevents h2o from going underground.

"Instead, the city's medication should absorption connected integrating drainage systems of buildings and streets to link them to reservoirs," helium says.

Increasing frequence of the rains has besides meant that forecasting agencies and catastrophe effect forces person little clip to respond to the crisis.

"Cyclones that utilized to instrumentality 2 to 4 days to make from a anemic tempest to an highly terrible cyclone are present intensifying successful little than a day's time," Dr Koll says.

That's why, helium adds, the authorities needs to formulate semipermanent policies that "help coastal communities accommodate to intensifying storms and rising oversea levels".

"We mightiness request to redesign cities to make much unfastened spaces and instrumentality measures for the flood h2o to sink."

Prof Janakarajan agrees - helium says the metropolis needs to conception much rooftop structures to harvest rainwater and store it underground.

"If that is done, Chennai volition not lone beryllium flood-resilient but besides drought-resilient."