River Ganga flowing along Patna breached the danger mark on Thursday for the first time this monsoon, posing flood threat for the state capital.

At 4pm on Thursday, Ganga was flowing at 48.64m above the riverbed at Gandhi Ghat around 8pm, where the danger level is 48.60m. Officials in water resources department said the river had a rising trend from Allahabad in the upstream in the past 48 hours. Officials said a further rise is likely over the next 48 hours. The Met has issued a forecast of light to moderate rain in and around Patna over the next two to three days.

"The water level has risen in the catchment area in the upstream of Ganga, which has led to increased discharge in the river in Bihar as well. As the water level was showing a rising trend in the upstream, including Allahabad and Varanasi till 4pm, we have issued a forecast of rising trend in the river water level along Patna over the next 24 hours," said Lakshman Jha, superintending engineer, flood control and drainage circle-Patna, water resources department.

The neighbourhood settled north of the 25-km-long flood protection wall of Patna faces immediate risk of flooding because of the rise in level in Ganga. Accordingly, the district administration has issued an alert for 48 hours for people settled between the river and the flood protection wall.

Patna district magistrate Sanjay Kumar Agrawal saidon Thursday: "We have issued a warning for people settled in the north of the flood protection wall to be vigilant on the rising Ganga. Though the water level along Patna is expected to recede in the coming days, people residing in buildings beyond the flood protection wall of the city would be forcibly removed, if required. We would be providing alternative accommodation to the affected people under such conditions."

Deliberating on preventive steps being taken to tackle a flood situation, Sanjay said: "We have formed a team of engineers who are closely monitoring the water level and a control room has been activated in Patna. A few teams of the state disaster response force have also been deployed at the ghats along Patna."

Apart from vicinities settled north of the wall, a threat of floodwater gushing into the city through the drainage outlets in Ganga also arises when the river inflates. Neighbourhoods situated on the northern periphery of the city, including Patliputra and Kurji, are the first few to face overflowing drains and waterlogged streets when the water level of Ganga reaches the outlets of municipal drainage leading to reverse flow.

The authorities are required to seal the outlet points of the big drains that discharge water in Ganga to stop the reverse flow. The district administration also shuts down the small drains constructed by residents on their own, which fall directly in the Ganga.