The devastation brought back memories of the 2015 deluge in the city — the disaster was a result of the heaviest rain in several decades and poor reservoir management. Here is a look at what happened in 2015 and how the latest flooding is different from the one caused eight years ago.
What happened in 2015?
The 2015 flood in Chennai was markedly different from the deluge on Monday. The deluge killed more than 200 people and submerged lakhs of homes.
The crisis began when the Chembarambakkam reservoir, near its full capacity, started discharging water into the Adyar river at an alarming rate. On December 1, 2015, consistent rains had filled the reservoir to 3,396 million cubic feet. By evening, engineers, fearing a breach, released water at 29,400 cusec (1 cusec unit equals 28.317 litres of liquid flow per second), a drastic increase from the 900 cusec outflow recorded at the month’s end.
This release, without adequate public warning, led to widespread chaos. By midnight of December 2, areas within a 4-km radius of the Adyar river were submerged.
Notably, the first heavy rain warning was issued on November 28, with a forecast of 50 mm rainfall, yet the outflow from Chembarambakkam wasn’t gradually increased. The situation exacerbated when two days later, Chennai received 200 mm of rainfall over 14 hours, exacerbating the situation.
The poor reservoir management was severely criticised — questions were raised regarding the overlook of earlier warnings and the sudden release of huge amounts of water without alerting the public or emergency services.
Therefore, the 2015 flood was more a result of reservoir mismanagement rather than natural climatic conditions, like this time.
What’s different this time?
Unlike the 2015 floods, the current flooding is a direct result of the cyclonic storm.
Chennai experienced a single-day rainfall of 24 cm on Monday, slightly less than the 29 cm recorded in 2015. However, the IMD categorises rainfall of 21 cm and above as “extremely heavy,” underscoring the severity of the current situation.
In a span of 35 hours starting from Sunday 8.30 am, Nungambakkam recorded a staggering 43 cm of rainfall till Monday evening, exemplifying the extraordinary nature of this climatic event.
How has Cyclone Michaung impacted Chennai?
The aftermath of Cyclone Michaung’s impact on Chennai and its neighbouring districts is marked by significant devastation. The cyclone led to eight deaths, and approximately 18,729 people including 6,000 within Chennai city limits, were moved to relief camps.
The relentless rains brought by the storm resulted in severe flooding. The Chennai airport, which is built on the flood-lanes of Adyar river, had to suspend operations, affecting nearly 300 flights and stranding over 1,500 passengers. Southern Railway also cancelled several long-haul trains, with others terminating at Chengalpattu. Many areas, particularly low-lying ones like Medavakkam, Keelkattalai, and Mudichur, remained submerged under 3-4 feet of water.
The Nandhivaram-Guduvanchery lake also reached its full capacity, leading to the flooding of nearby residential areas. The Chennai-Tiruchy highway was severely affected and the ground floor of the Chromepet government hospital was inundated.
Power supply was suspended as a precaution from Sunday night. Despite efforts by the Chennai Corporation and other government agencies, many roads were impassable on Monday, and widespread power outages were reported.
The impact of Cyclone Michaung also severely disrupted telecommunications in Chennai, halting essential communication networks including phone services, cellphone networks, and the internet. Many telephone exchanges across Chennai blacked out, affecting internet services and mobile connectivity, leaving residents struggling to connect with work or loved ones.
While major exchanges functioned using generators after the blackout by Tangedco, the state-owned power company, minor exchanges in low-lying areas faced issues. Exchanges in Tambaram, Adyar, Kellys, and Velachery were particularly affected, with equipment shut off to prevent damage from inundation.
Why is Cyclone Michaung’s impact so severe?
Talking to The Indian Express, S Balachandran, Deputy Director General of Meteorology at the India Meteorological Department (IMD), attributed the severity of the situation to three primary factors.
First, the cyclonic system Michaung’s proximity to the coast significantly amplified its impact. At its closest, it was merely 90 kilometres away, a distance alarmingly closer compared to previous cyclones.
Second, the system exhibited an unusually stagnant movement. What typically moves at speeds between 10 to 18 kph slowed down to a mere 7 kph, further dropping to an almost standstill pace of 5 kph.
Third and perhaps most critical factor was the intensification of the system while it was stationary. This intensification, occurring so close to the coast, led to heavy and prolonged downpour. The slow-moving nature of the system resulted in increased wetness, exacerbating the situation.
How have authorities responded?
As Chennai faced an onslaught of rain on Sunday night and Monday, the city’s water management became critical. The WRD was closely monitoring the Chembarambakkam Lake, a crucial reservoir.
Responding to the escalating situation, the WRD increased the release of surplus water from 6,000 cusecs to 8,000 cusecs. This was followed by a phased discharge strategy, as the inflow surged to an alarming 12,000 cusecs. The department then began discharging water at an increased rate of 500 cusecs every half hour, eventually ramping it up to 1,000 cusecs.
Additionally, at the Poondi reservoir, another significant water body, authorities discharged 17,000 cusecs of water due to an inflow of around 6,000 cusecs from its catchment area.
Indian Army personnel evacuate stranded residents from a flooded colony during heavy rainfall due to Cyclone Michaung, in Chennai district, Tamil Nadu. (PTI Photo) 
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