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Why did Bengaluru suffer in the rain?

Rescue team helping Shanti Nagar BMTC workers after heavy rain on Independence Day Early hours in City low lying areas in Bengaluru on Tuesday (15/08/2017).  

Why the deluge?

With unprecedented rainfall lashing the city over the past couple of months, Bengaluru is battered and bruised. Not only has the rainfall broken records, making it the city’s wettest year, it may also be one of the deadliest. So far, over 16 persons have died since May, apart from at least five persons who were killed in road accidents caused by potholes that have sprouted after the rain abated. Houses collapsed, lakes overflowed, and major roads were inundated. Is Bengaluru afraid of the rains?

How intense were the rains?

The city has received more than 1,660 mm of rain since January, more than any year since the India Meteorological Department (IMD) started its monitoring station at the end of the 19th century. Last year, when many parts of Karnataka witnessed drought-like conditions, it received around 1,100 mm in the whole year. However, this year’s rainfall has been erratic to say the least. After strong pre-monsoon spells in May, the first two months of the monsoon were unusually dull with just 83 mm and the prospect of another drought year raised its head. These anxieties were washed away in mid-August, with the night of August 14 seeing nearly 129 mm of rain. For the next two months, near incessant rainfall has lashed the city, with the rain gauges recording in excess of 1,200 mm — 25% above the average annual rainfall.

What has the impact been?

Much of the IT hub remained inundated, lakes overflowed into houses in many areas. Roads were flooded, and then developed potholes — over 35,000, according to the Bruhat Bengaluru Mahanagara Palike (BBMP). Around 90% of the potholes have been fixed, and most major roads are in a decent state now. In the first six months of the year, the BBMP undertook road works amounting to ₹374 crore. On the patchwork after monsoons, it spent around ₹20 crore. On average, the civic body spends around ₹600 crore each year on road works — apart from special grants from the State government for road-widening or flyovers and footpaths.

What about the water crisis?

Rain in Bengaluru is not entirely linked to water crisis. Bengaluru gets its drinking water from the Cauvery basin, which requires rain in the Western Ghats. Water levels in the reservoirs are much higher than they were last year, so no water crisis is expected.

Why did the city get flooded?

Rainfall figures hide a deeper truth of the nature of this season’s monsoon. Meteorologists point out that heavy spells of rainfall — where over 12 mm is recorded in an hour — were unusually common this season. Meanwhile, the urban heat island effect also saw some parts of the city — the heavily concretised landscapes of south and east Bengaluru, for instance — receiving far more rain than the relatively green north Bengaluru. That the city has expanded beyond its means has contributed to the problem. Stormwater drains that crucially connect between lakes are badly designed or have been encroached upon or choked with sewage and garbage. Lakes have been lost and whatever exists has been lined with sludge, reducing the capacity to hold excess rainwater. Layouts and rampant construction have propped up in natural depressions of the city — all of which leave the water with no place to go but into houses.

What can be done?

Civic experts point out that reviving numerous lakes, including the nearly 1,100-acre Bellandur and Varthur lakes, is critical to ensuring that the city can sustain rain such as this year’s. Besides allowing for storage of over five thousand million cubic feet of water, these lakes ensure that more than double their storage capacity percolates to the soil.

Interlinking these lakes is a stormwater drain system that utilises the city’s terrain to transfer water from the catchments to another. However, out of 853 km of stormwater drains, only 400 km has been strengthened. Moreover, the completed drains have all-concrete lining. This means the rainwater gushes to lakes rather than percolate into the surface. Whether the rain has intensified due to climate change — which means stronger downpours and more erratic monsoons — or 2017 was just an anomaly, what is for certain is that unless the infrastructure is overhauled, Bengaluru cannot cope with rain.


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Printable version | Jun 19, 2021 10:02:59 PM |

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