The heaviest spell of overnight rain on Monday came at a time the sluice gates that drain out rainwater from Calcutta into the Hooghly were closed because of high tide in the river, engineers of the Kolkata Municipal Corporation (KMC) said.

High tide in the Hooghly means the water level in the river rises above the height of the underground drainage lines that carry the city’s rainwater. If the sluice gates are not closed, water from the river will flow back into the drainage network and inundate roads.

“The sluice gates were closed between 1.30am and 5.30am on Monday,” said a KMC official.

The city received the maximum volume of rain between 11.30pm on Sunday and 4.30am on Monday, said another official.

The simultaneous occurrence of the two meant that the rainwater kept accumulating inside underground drainage lines and when the drains were filled, water started flooding roads. “The rainwater started to go down once the sluice gates were opened around 5.30am,” said an engineer.

All the water would have receded by afternoon but more rain and another round of high tide beginning late afternoon repeated the sequence of the previous night.

Camac Street, Park Street, Shakespeare Sarani, Pretoria Street, Thanthania, MG Road, AJC Bose Road, Chowringhee Road, Bidhan Sarani and Central Avenue were some of the arterial roads whose stretches were waterlogged till early evening.

“If it does not rain anymore, we will be able to drain out water from all roads by Tuesday morning,” mayor Firhad Hakim said on Monday evening after reviewing the situation with engineers.

Multiple roads in Salt Lake were waterlogged through the day.

Both flanks of a 2km-long stretch of VIP Road, bet-
ween Haldirams and airport gate number 1, was under water. The service lanes on both sides were waterlogged, too.

A resident of Koyla Vihar, near Haldirams, said many of her neighbours had to return home after they were unable to drive their cars through the waterlogged road fearing a breakdown.

A drive through the city showed uprooted or broken branches lying on roads. In some places, emergency workers had cut the trunks into smaller pieces and kept them on the roadside.

Over 400 trees were uprooted in Calcutta, Salt Lake and Howrah, officials said. About 280 trees were uprooted in Calcutta, about 120 in Bidhannagar and close to 25 in Howrah city.

Branches of more than 150 trees broke in Calcutta, said a KMC engineer.

A large tree fell at the intersection of Russel Street and Park Street in the afternoon, blocking the crossing. Another tree fell on Cathedral Road blocking the flank closer to Mohor Kunja.

Chainsaws were used to cut the trunks and the branches into smaller pieces and open the roads to traffic. At the Park Street-Russel Street crossing, the tree pulled down a bunch of cables and the rails along the footpath leaned on the road.

A chimney of a defunct factory in Baranagar, next to St James’ Church on Kashinath Dutta Road, collapsed early on Monday on a series of cars. All the cars were smashed.

The premises of the Calcutta Medical College and Hospital remained flooded till late afternoon.

Power supply was cut off in many places, including Ajoynagar, Sinthee, Lake Town and stretches along Purbachal Main Road, Sarat Ghosh Garden Road and Maniktala Main Road.

Parts of Howrah, including Sankrail and Baje Shibpur, also went without power.