Jammu: Authorities sounded a flood alert on Sunday after incessant rains continued for over 24 hours in Jammu city, causing many rivers and water bodies to swell. "A flood alert has been sounded and all departments concerned with flood protection duties were asked to keep their field staff ready," a district administration official said here. "The Tawi river was flowing at 18 feet on Sunday morning, which is the danger mark," an official said. "Chenab river was flowing above the danger level at 30 feet," he added. Landslides in the Ramban district have blocked the Jammu-Srinagar national highway. Traffic on the highway has been suspended on Sunday, the official said.