Persistent rain from Saturday night to 11 am on Sunday caused streams to overflow and inundated several roads in Ngoc Chien and Muong La communes.
Floodwaters and landslides blocked roads, while erosion damaged several bridges, disrupting traffic. The road linking Chom Khau and Ke villages to Muong La was among the worst affected.
In Muong La, flooding along the Nam Pam Stream damaged crops and other property.
Initial estimates showed more than 20 hectares of rice fields, 700 metres of irrigation canals and five houses were damaged.
Rainfall exceeded 249 mm in Nam Pam, 147 mm in Chieng Muon and 134 mm near the Nam Chien hydropower plant, according to local monitoring stations.
Heavy rain was also recorded in Ngoc Chien, Xim Vang, Hua Trai and Ta Xua, raising the risk of flash floods and landslides.
Local authorities said they were clearing landslides, restoring transport links and assessing the damage, while urging residents to avoid flooded crossings and move to safer areas if signs of flash floods or landslides appeared.