Assam was hit by the first wave of flood with the Brahmaputra's tributary Jiadhol rising alarmingly in the flood-prone Dhemaji district yesterday. Officials said in Dhemaji that heavy rainfall for the last few days has led to the water level of Jiadhol river to rise alarmingly affecting more than 20 flood-prone villages of the district. A section of National Highway-52 was also submerged at Samarjan with traffic stranded on the way. The district administration has sounded an alert and efforts are being made to ensure traffic movement along NH 52.