Sobo’srainofterror onwedworsethan’05 Flood forecasting system didn’t help
South Mumbai got 331mm rain, compared to 73mm on July 26, 2005, the day city was marooned
South Mumbai on Wednesday received more rain than during the July 26, 2005 deluge, with a maximum wind speed of 101kmph making the situation “hurricane-like” and “unprecedented”, according to the Brihanmumbai Municipal Corporation (BMC). The city was marooned and more than 1,000 people died in the 2005 monsoon mayhem.
According to the India Meteorological Department (IMD), Colaba had recorded 73mm of rain in 24 hours during the 2005 deluge, compared to 944mm in Santacruz. Compared to this, Colaba recorded 331mm rain and Santacruz recorded 162mm in 24 hours between Wednesday and Thursday morning. The civic body said the current capacity of drains is good enough for average or above average rain, but can’t handle an extreme situation like that on Wednesday. BMC said it will explore the possibility of having a holding pond or underground water tunnel to contain the floodwater in south Mumbai.
On Wednesday, upscale localities of south Mumbai such as Marine Drive, Chowpatty, Grant Road, Mumbai Central and Marine Lines witnessed heavy waterlogging. The National Disaster Response Force (NDRF) had to even use boats to rescue passengers stuck at Masjid Bunder Railway station, which was completely under water.
According to the IMD’S threehourly bulletin, between 8.30am and 11.30am on Wednesday, Colaba recorded 51mm of rain, which increased to 120mm by 2.30pm, 229mm by 5.30pm, 293mm by 8.30pm, 328mm by 11.30pm and 331mm by 8.30am on Thursday morning, indicating 242mm of rain in a period of nine hours between 11.30am and 8.30pm on Wednesday in Colaba.
In a statement issued on Thursday, IMD stated: “Mumbai received widespread rainfall with scattered heavy to very heavy rainfall with extremely heavy rainfall at isolated places. Colaba reported the highest rainfall of 331.8mm in 24 hours, breaking its earlier record of August. This is also the second highest all-time record over Colaba after 575.6mm (July 5, 1974).” On the other hand, Santacruz observatory of IMD recorded 32mm of rainfall between 8.30am and 11.30am on Wednesday, followed by 42mm by 2.30pm, 65mm by 5.30pm, 103mm by 8.30pm, 138mm by 11.30pm and 162mm by 8.30am on Thursday.”
MUMBAI :
P Velrasu, additional municipal commissioner, said, “Every area has different capacity and in south Mumbai, the drains have capacity to hold 50-60mm of rain in a period of 60 minutes, which is suitable for average or above average rainfall. What we witnessed on Wednesday was an extreme situation considering our drains in areas like chowpatty are well-maintained, but did not work owing to the rain.”
“Our system can’t cope with an extreme situation like that of Wednesday, and we definitely need to re-look at our strategy. We have to undertake augmentation of our facilities by correlating with the current rain pattern, and this is a process that will take five-10 years. There are no short-term measures for stormwater drainage, apart from increasing dewatering pumps post accumulation of water, which we have already done. We have initiated a process to have the capacity to handle around 90mm of rainfall per hour. Having underground water tunnels in south Mumbai is one of the solutions.”
BMC had initiated a plan for holding ponds in the form of underground water tunnels to divert the excess rainwater for a temporary period, from where they can be drained out further into the sea or put in use by transferring rainwater to the treatment plants of BMC.
Experts claimed that waterlogging, even after projects such as the ₹4,000-crore Brimstowad launched post 2005 being completed, hinted that the drains were not properly cleaned. Brimstowad project includes rehabilitation and augmentation of underground drains in the city from handling 25mm of rainfall per hour to 50mm of rainfall per hour, widening and deepening of nullahs, construction of access road along the nullah and construction of stormwater pumping stations. BMC’S data stated that 36 of the total 58 projects planned under Brimstowad have been completed, which include 19 of the 21 projects planned for south Mumbai.
Nikhil Desai, advanced locality management (ALM) from Matunga, said, “The inefficiency of BMC is clearly out, considering it seems that owing to Covid-19 the cleaning of drains was not done properly.” Velrasu said, “There was no water accumulation owing to choked drains. The intensity of rainfall was very high. We had used around 175 pumps. Meanwhile, BJP on Thursday demanded BMC compensate citizens whose houses were damaged
Bandra
Marol
Vile Parle
Versova
Dindoshi
Kandivli
Nariman Point
BMC headquarters, Fort
Memonwada fire station, Bhendi Bazar
Malabar Hill
Mandvi Fire Station, Masjid Bunder
Byculla
MUMBAI: The city’s flood forecasting system was unable to assist the civic body during the exceptionally heavy rain on Wednesday, the Brihanmumbai Municipal Corporation (BMC) said.
Inaugurated on June 12, the integrated flood warning system for Mumbai (iflows-mumbai), the second for any urban city (after Chennai) in the country so far, was developed to provide possible extent of flooding in Mumbai three days prior to heavy rain events and warnings to areas susceptible to flooding across all 24 wards 12 hours in advance. The system was launched on a trial basis this monsoon and based on its success, it was to be made public next year.
“The system is not fully functional and not handed over to BMC yet. Although it is being used on an experimental basis, it did not provide any alerts to us about possible areas to be flooded 12 hours in advance. We were only aware about the extremely heavy rain event three days prior. No bulletin was issued either on Tuesday or Wednesday,” said BMC’S disaster management chief officer Mahesh Narvekar, adding Wednesday’s rainfall and unprecedented wind speed was the most severe weather event witnessed in south Mumbai over the past two decades. “There was no prior intimation of extremely high wind speed that caused the tree fall and infra damage,” said Narvekar.
Since its launch, IMD made public the flood warning bulletin on July 3, 14 and 15 that issued warnings for 656 spots across 24 wards in the city, dividing them into categories ranging from low probability (less than 1-ft depth), moderate (1-2ft depth), high (2-3ft depth) and very high (over 3-ft depth). “These warnings for Wednesday could have helped direct our manpower to locations faster. However, there is a difference in issuing the forecast and the ground reality. In all, over 200 tree fall incidents were reported across south Mumbai, and major flooding was reported from 25 spots that took seven hours to recede,” said Narvekar.
The system was jointly conceived by various departments of the Ministry of Earth Sciences (MOES) and BMC. “I was recently informed about some technical issues at our observatories due to the pandemic. At a couple of observatories, people were unable to repair them. We will crosscheck what happened,” said M Rajeevan, secretary, MOES. IMD director-general Mrutyunjay Mohapatra said, “Wind warning for the port and fishermen identified maximum wind speed at 70-80kmph. The IFLOWS system is being studied on an experimental basis, and we will check for technical problems.”
Additional municipal commissioner P Velrasu said the accuracy of advanced warnings using the system need to be validated with ward units. A senior BMC official said that on Friday they are holding a meeting with the National Centre for Coastal Research (NCCR), one of the MOES bodies, for further deliberations about the project.