Rapid urbanisation, pollution worsen effects of October rains in Bengaluru

With 18 days still left in October and weather experts talking of another week of intense rain, Bengaluru is headed for the wettest October in at least over the past two decades.

Bengaluru is expected to see moderate to heavy rainfall till October15, for which a yellow alert has been issued by the India Meteorological Department. Photo: PTI

Bengaluru is inundated. Nor surprising given how Indian cities lack drainage systems, but surprising because the city is marooned in October.

Heavy rain on Monday night led to waterlogging on the roads leading to Bengaluru International Airport where cabs and private vehicles, including buses, were left stranded while 11 departing flights were delayed due to adverse weather conditions till 10 pm.

Bengaluru airport, which received 178.3 mm of rain on Monday, came to a standstill as areas near the pick-up and drop points were inundated. The situation was so bad that some passengers were ferried on a tractor to the airport. 

The Bangalore International Airport Limited (BIAL) spokesperson commented that since its start of operations in 2008, the airport has not seen such unprecedented rain on a single day. 

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Meanwhile, a man reportedly lost his life due to a short circuit in a house that was flooded after heavy rains in Konappana Agrahara, said Bengaluru west police on Tuesday (October 12). 

The rainfall this year has not been uniform with some months recording more than average rainfall. Even in the month of October, the city is receiving heavy rains. Bengaluru is expected to see moderate to heavy rainfall till October15, for which a yellow alert has been issued by the India Meteorological Department (IMD).

With 18 days still left in October and weather experts talking of another week of intense rain, Bengaluru is headed for the wettest October in at least over the past two decades.

What’s causing the downpour in Bengaluru this October

An official at the IMD told The Indian Express that the trough between cyclones over Bay of Bengal and Arabian Sea have caused the October downpour. “The trough is passing through north interior Karnataka. The low pressure developing in the Bay of Bengal is also contributing to this. In the next 48 hours, Bengaluru will receive thunderstorms. Every year during the month of October and November we witness a similar situation.”

From October 1 to 9, Bengaluru Urban district recorded 78 mm rain as against the normal 61mm, excess of 28 per cent, according to the Karnataka State Natural Disaster Monitoring Centre (KSNDMC). 

According to the IMD, Bengaluru receives heavy rainfall every year during the months of October and November. In October 2005, the city received 605.6 mm of rainfall. On October 6, 2017, Bengaluru witnessed 76.6 mm of rainfall in 24 hours and 385.7 mm of rainfall for the entire month.

Also read: Heavy rains expected in 7 districts of Kerala till October 15

While heavy rains in October and November months is an annual phenomenon, what seems to be making it look so bad is increasing flooding of areas restricting traffic. The Bruhat Bengaluru Mahanagara Palike (BBMP) has identified 209 areas prone to flooding. As many as 153 of these have been identified as sensitive and 53 extremely sensitive. Parts of Bengaluru, which fall in the low-lying areas, witness flooding.

Allegations are that while BBMP identified the sensitive zones, it took no action to address the problem.

An ENVIS Technical Report titled ‘Frequent Floods in Bangalore: Causes and Remedial Measures’ says, “Urban flooding is a consequence of increased impermeable catchments resulting in higher catchment yield in a shorter duration and flood peaks sometimes reach up to three times.  Thus, flooding occurs quickly due to faster flow times (in a matter of minutes). Causal factors include combinations of loss of pervious area in urbanising landscapes, inadequate drainage systems, blockade due to indiscriminate disposal of solid waste and building debris, encroachment of storm water drains, loss of inter connectivity among lakes, housing in floodplains and natural drainage and loss of natural flood-storages sites.”

The reports further says, “Bangalore is experiencing unprecedented urbanisation and sprawl in recent times due to concentrated developmental activities with impetus on industrialisation for the economic development of the region. This concentrated growth has resulted in the increase in population and consequent pressure on infrastructure, natural resources and ultimately giving rise to a plethora of serious challenges such as climate change, enhanced green-house gases emissions, lack of appropriate infrastructure, traffic congestion, and lack of basic amenities (electricity, water, and sanitation) in many localities, etc.”

Urban heat island: Why some parts receive heavy rains and others less

This study shows that there has been a growth of 1028 per cent in urban areas of Greater Bengaluru over 45 years from 1973 to 2017. The urban heat island phenomenon is evident from the large number of localities with higher local temperatures.

Also read: In climate change fight, here’s how India can exceed Paris accord targets

Experts say that due to increased urbanisation, the radiation of excess heat in the city contributes to cloud formation. Pollution also contributes to the variation of rainfall patterns in the city. Temperature too varies across the city. South and East Bengaluru have large pockets of industries, IT companies and residential houses which results in high temperatures. 

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