Guwahati: Simultaneous extreme rainfall in Nagaland and the adjoining plains of Assam triggered devastating flash floods in three districts of upper Assam, chief minister Himanta Biswa Sarma said on Friday.“When Mokokchung, Wokha and Mon in Nagaland received exceptionally heavy rainfall, Charaideo in Assam simultaneously recorded rainfall that was 436% above normal. At the same time, Sivasagar received 134% excess rainfall between July 18 and 20. This meant that while huge volumes of water were flowing down from the hills into Assam, the plains were also receiving intense rain, leaving little room for drainage and triggering the devastating flash floods,” Sarma said.India Meteorological Department data showed Mokokchung received 238.9 mm against the normal 40.3 mm — an excess of 493%.Sarma said heavy rainfall in Dibrugarh, Jorhat and parts of Arunachal Pradesh aggravated the situation as the Brahmaputra was already carrying a high monsoon discharge.Hydrologists said runoff from river systems originating in Nagaland and Arunachal Pradesh rapidly converged in Brahmaputra tributaries, while the swollen river slowed their drainage.The state govt plans a hydrological assessment and discussions with neighbouring states on weather monitoring, real-time rainfall data sharing, reservoir management and advance flood warnings. Officials said coordination among Assam, Nagaland and Arunachal was essential to mitigate similar events.
