A well-marked low pressure that had formed over the northwest Bay of Bengal, off northern Odisha and Bengal, moved westward and intensified into a depression, causing “very heavy” rainfall with gusty winds across south Bengal throughout Sunday.

According to weathermen, the depression that lay 10km southeast of Digha and 90km east-northeast of Balasore, is set to cause heavy rain in several districts on Independence Day too, with a windspeed of 50 kmph.Rain on Sunday led to a flood-like situation in many areas in South 24-Parganas, North 24-Parganas and East Midnapore.

Gusty winds pushed up river water in the Sunderbans delta that breached many earthen dykes, flooding homes and farms.Kakdwip and Canning subdivisions in South 24-Parganas were the worst hit. Sandeshkhali and Hingalganj blocks in North 24-Parganas also saw major inundation.

The sea in Digha and Mandarmani was turbulent. Though the administration banned sea-bathing, Subhaprasad Mondal, a tourist from Ghatal, entered the water. He was rescued by civil defence personnel.Chief minister Mamata Banerjee. on Sunday said: “Overflowing waters of the Ganga have assumed a catastrophic, flood-like proportion in South 24-Parganas, the Sunderbans, and even North 24-Parganas.... with several dams breached…. What was slated to happen in Odisha happened in Bengal.”

She asked people to stay careful over the next 24 hours. The IMD office in Calcutta has said the situation is likely to improve on Tuesday.