The rapid urbanisation in the last two decades, and reduction of water bodies and green cover has contributed greatly to the change in climate conditions, according to environmentalists.

Hyderabad Rains in which some people are walking with umbrellas and some were driving in vehicles amidst inundated roadsImageCredits_PTI
news Climate Change Tuesday, October 19, 2021 - 11:07

This story is among several stories from TNM that will highlight the inundation, flooding and other consequences of heavy rains in Hyderabad. TNM hopes to draw attention to these issues, which have now become perennial in many areas of the city, by talking to experts, officials and more.

On the night of October 8 this year, Hyderabad recorded heavy rainfall of about 100 mm in the span of a couple of hours in parts of the city including Secunderabad, Saidabad, Moosapet and Saroornagar, among others. Climatologists say that this amount of rainfall is usually spread over a span of a day or two. Describing this as ‘microbursts’ or ‘mini’ cloudbursts, they say the city is facing the impact of the phenomenon due to global warming and climate change.

A cloudburst is defined by the India Meteorological Department (IMD) as intense rainfall measuring 100 mm per hour over a localised area, not exceeding 20-30 square kilometers. While some meteorologists have suggested that receiving more than 50 mm of rainfall in a span of two hours may be called a mini cloudburst or microburst, there is no clear definition of this weather phenomenon. Moreover, IMD has said that forecasting such cloudbursts is far from easy, given the highly localised nature of these weather events.

Change in rainfall pattern

According to data from a report titled ‘Weather and Climatology in Telangana’ from the Telangana State Development Planning Society (TSDPS), the high-intensity rainfall phenomenon is recent and has increased in the last two decades.

If we observe the occurrence of highest rainfall in a 24-hour period in Hyderabad in the last hundred years, four out of five highest rain events were reported in the last two decades. While Hyderabad and its surrounding districts, including Rangareddy, Medchal and Malkajgiri, received the record highest rainfall in a 24-hour period – 431.8 mm – from September 1908, this was followed by 241.5 mm in Begumpet on August 24, 2000, 226.8 mm in Saroornagar on July 21, 2012, 230.2 mm in Quthbullapur on September 21, 2016 and 300 mm in Hayathnagar on October 10, 2020.

Hyderabad city itself witnessed the top three spots of highest rainfall in 24 hours in the rains that wreaked havoc in October 2020. On one day – October 14, 2020 – 258.3 mm rainfall was recorded in Musheerabad, 252.4 mm in Saidabad and 248.3 mm in Bandlaguda.

What climatologists say

Mahesh Palawat, Chief Meteorologist from independent weather agency Skymet, says these extreme weather events are likely to increase in intensity and frequency due to climate change and global warming. “Now the air is warming up due to an increase in global temperatures. So the capacity to carry moisture is also higher, which leads to microbursts and intense thundercloud development, which usually leads to intense rainfall or heavy downpours for two to three hours,” he says.

Elaborating on microbursts, Mahesh says, “Microbursts have been observed for the last 4-5 years and we’re going to see more of it in the next 10-12 years.”

Mahesh points out that extreme weather events have increased significantly due to climate change and global warming. He explains, “The rainfall pattern has also changed. Earlier it used to be uniform rainfall, now heavy rainfall in short duration is more common. Heavy rains have decreased but the intensity has increased. Microbursts have also increased, the amount of rainfall that used to occur in the span of two to three days is now occurring in 24 hours or sometimes even 5-6 hours.”

Meteorologists also say that weather systems developing over the Bay of Bengal have changed in recent times, and this in turn is impacting Telangana. “The occurrence of extreme weather events has increased in Hyderabad. The weather system developing over the Bay of Bengal used to travel in a north-westerly direction earlier – across Odisha, Chhattisgarh, Madhya Pradesh, sometimes over Uttar Pradesh. Now it is taking westerly trends, over Odisha, Telangana and Vidarbha. That’s why the intense rain activity has also increased in Telangana, particularly during the monsoon season. And the rain activity is not limited to July, August and September, it also extends into October and November,” he explains. 

IMD Hyderabad Centre Director K Nagaratna agrees that the city has been seeing a change in the rainfall pattern. “Yes, the rains in October 2021 were microbursts, but we could not do proper research due to lack of manpower. For the last few years, we have been observing rainfall of short duration and high intensity. More studies need to be done in this regard,” says Nagaratna.

Causes of climate change specific to Hyderabad

Environmentalists who have been doing studies in the city over the years say that the rapid urbanisation and growing population alongside pollution are some of the main reasons for the changes in the weather.

Hyderabad-based environmentalist BV Subba Rao points out that the city has witnessed rapid concretisation in the last two decades and the fastest growth was observed in the last 10-12 years. However, he adds that the development happened without any regulations or restrictions over which area should be developed, what kind of buildings should come up, and what material should be used. This, he adds, resulted in a lot of violations.

This rapid, unregulated growth has resulted in Hyderabad flooding after short, intense spells of rainfall. “On one side is unregulated concrete development, on the other side is the shrinkage of open spaces, parks and lakes. The lakes, which regulate the microclimate and keep the surroundings cool, have been lost over a period of time. More than 50% of lakes are now gone. So, the net result is that the city has become a radiation pocket, so more the radiation, more the water evaporates and the area becomes a vacuum. It sucks the clouds, especially rain-bearing clouds, so that’s why we’re experiencing these sudden outbursts,” Subba Rao explains.

Subba Rao notes that last week Secunderabad received 70 mm of rain in one hour, so the trend is changing to sudden outbursts of rain in pockets. “The outbursts of rains are in certain pockets, one day in Secunderabad, one day in Malakpet, so we’re not experiencing widespread rain, the trend is changing to high-intensity, short duration rainfall,” he says.

But in these circumstances, the environmentalist wonders whether the city is prepared, as there are not enough lakes to receive all that water, which is resulting in many areas getting submerged and inundated under flash floods.

Syed Azeem Unnisa, Professor at the Department of Environmental Sciences in Osmania University, Hyderabad, points out that the city’s growing population is also adding to our climate woes. “The population in the city is growing exponentially and the space is shrinking. As a result, more new buildings are coming up to accommodate them, more vehicles are being used for transport. A lot of pollutants are being released into the atmosphere, be it carbon dioxide or methane from industries or vehicular pollution. The state should bring in measures to curb the same.”

Subba Rao adds, “The rapid urbanisation going on in Hyderabad is establishing heat pockets. Even while it’s raining, the temperatures are not cool, so that is a change in the typical Hyderabad weather. Probably similar changes are happening in other cities like Bengaluru, Pune and Nagpur among others. Despite these unfortunate changes, the Urban Planning Department does not seem to have learnt anything. We do not have experts, especially in hydrology, climatology and other related fields, set up in the Department. So how can the administration plan when they are not equipped at all? The only manpower they have are those who go and open manholes whenever it rains. This is the greatest skill our people exhibit in the midst of a crisis!”

Can the city tolerate more rains? What can be done?

Subba Rao says, “The importance of water bodies like lakes becomes much more relevant in cities now. The kind of havoc Hyderabad has faced in the last three years due to the high-intensity rains is unprecedented. There is a need to study, analyse and understand the change in rainfall and reorient the water management in the city to make it suitable for living.”

Subba Rao, who has studied rainfall data for the last 30 years, says that the incidence of cloudbursts and microbursts is increasing. During the October 2020 rains itself, there were seven to eight localised cloudbursts in Hyderabad.

Anant Maringanti, Executive Director of city-based research and action initiative Hyderabad Urban Labs, points out that a Special Cell headed by a designated Lakes Commissioner was recently formed to protect the 185 lakes and water bodies in Hyderabad. “The Lakes Commissioner has to know what is happening by working with various departments and initiate measures accordingly. Wherever there could be floods and inundation, the authorities should first identify those hotspots and find the reasons. They should work with people to bring in change, local residents will know what the problem is. If my house is inundated, I’ll try to find its cause,” Ananth says.

Also Read: Half of Hyderabad would be submerged if it rained for 17 days, says study

Also ReadHyd has a plan to fix nalas — but the city flooded, thanks to delay in implementation

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