Torrential rains and high tide lead to widespread flooding across Kolkata

Rising river levels caused the gate to close, Calcutta Municipal Corporation engineers say

Subhajoy Roy



Posted on 18.06.21, 02:55

Torrential rains and a high tide, which prevented water from flowing into rivers, caused widespread flooding across the city on Thursday, engineers from the Calcutta Municipal Corporation said.

Ten drainage pump stations in the city recorded more than 100mm of rain from 10 p.m. Wednesday to 6 a.m. Thursday. Five of them recorded more than 150 mm of rain during the period.

Data shared by Calcutta Municipal Corporation (CMC) showed Mominpore Drainage Pump Station recorded 179mm of rain, Kalighat Drainage Pump Station 168.2mm, Behala Flying Club Station 163.6mm,

Topsia 153mm station and Chetla Lockgate 150mm station.

Almost all of Kolkata was flooded as dawn broke on Thursday due to heavy rains overnight.

A waterlogged theater road on Thursday afternoon.

Central Avenue, Colootolla, Park Street, JL Nehru Road, Camac Street, Queens Park, Lake Gardens, Southern Avenue and Kasba were among the hardest hit.

Some of the city’s pockets that are not usually waterlogged, such as Loudon Street and Rawdon Street, were flooded on Thursday.

An engineer blamed the widespread waterlogging on the high volume of rain overnight and the high tide the following morning, which failed to let water flow into the Hooghly and Bidyadhari rivers.

“The city received maximum rain from 10:00 p.m. Wednesday to 4:00 a.m. Thursday. We were able to drain a lot of water as the Hooghly gates stayed open until 4am. It was closed at 4am and reopened at 8am. The gates were closed again between 4:30 p.m. and 8:30 p.m.,” said Tarak Singh, a CMC board member who heads the drainage service.

But the volume of precipitation far exceeded the water’s capacity to drain away. Kolkata’s underground drainage system is designed to prevent waterlogging only if it rains up to 6mm in an hour, an engineer has said.

A flooded Lake Gardens on Thursday afternoon.

Capacity is increased by installing more pumps. “The water could not be evacuated after 4 am. In addition, more rain added to the volume of accumulated water. The water was drained from most roads by the afternoon,” Singh said.

Rainwater accumulated in the city naturally flows west into the Hooghly and east into the Bidyadhari after passing through drainage pump stations.

Gates through which water passes into the rivers had to be closed for several hours on Thursday as water levels in the rivers were too high due to rain and high tide.

“Whenever there is heavy rain, the Hooghly sluices are opened so that some of the rainwater is drained into the river. This reduces the load on drainage pumping stations. It becomes a problem when heavy rains coincide with high tide,” the engineer said.

Loudon Street

“At high tide, the water level in the Hooghly is higher than the level of the drainage pipes. If the gates are kept open, the water from the Hooghly will flow back into the drainage system and only worsen the clogging. This is why the locks must remain closed at high tide in the Hooghly.

A similar system is followed in the operation of locks in the Bidhyadhari River.

Singh said if it didn’t rain at night, the remaining water would be drained in the morning.

“Most of the water receded in the afternoon. Some places were waterlogged until the evening, probably due to other issues like blocked drains,” he said.

Some gully pits were blocked with plastic and polythene bags, which further slowed the evacuation of water.

In Behala, the waterlogging was blamed on the inability of the civic body to operate the Behala Flying Club’s drainage pump station. Singh said people living along a canal into which the pumping station is pouring water protested, saying water from the canal was entering their homes.

“We hope we can get the station pumps running soon,” Singh said Thursday evening.

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