Development activities in the neighboring hill state of Assam without hydrological studies and appropriate environmental protection measures have further worsened the flood situation in the plains, especially during heavy rainfall. Arup Kumar Sharma, Professor of Civil Engineering, IIT Guwahati and Hydrologist, Assam floods have affected infrastructure construction and mining in Arunachal Pradesh, Nagaland and Meghalaya.
Regarding the impact of road construction, massive logging for mining and other infrastructure activities in hilly areas, Prof. Sharma said such activities can change flood conditions in plains without proper hydrological studies and restoration of vegetation cover. He mentioned that due to heavy rainfall in the hilly areas, the amount of water and silt increases. Also, faulty road crossings cause floods and landslides, he pointed out. Roads lack open space for mountain streams, which disrupt communication and cause artificial flooding by water accumulation on flat roads.
He cited the recent unusual floods in southern Assam and the Khanapara-Zorabat area of Guwahati as two main reasons. The first reason is massive deforestation in the Awahika region south of the river. Satellite images show that activities in Arunachal Pradesh have affected Sibsagar and Jorhat, Dhemaji and Dibrugarh, and Khanapara, Zorabat and Guwahati due to deforestation in Meghalaya. This deforestation due to mining and road construction has reduced the water and sediment carrying capacity of the rivers and the silt accumulation has turned the rivers into torrents.
Changing rainfall patterns due to climate change further complicates the situation. Professor Sharma said, due to climate change, more intense rainfall is now being felt. El-Nino usually acts as a factor in low rainfall, but its influence in the Eastern Himalayas this year cannot be denied. Cyclonic moisture from the Bay of Bengal over Nagaland and Manipur hit the hilly areas and caused heavy rainfall. Incessant rains lead to soil saturation and heavy rains in barren areas lead to abnormal runoff.
Referring to the flood situation in the hilly areas like Karbi Anglong and Dima Hasao districts, he said, similar rains may inundate the plains of these districts. He said that the dam authorities were forced to release excess water during heavy rains. Hence, regular monitoring of flood conditions is necessary to send early warnings and reduce flood disasters. He emphasized on the need to form a coordinating committee comprising academicians, catchment authorities and concerned district administrations covering hilly and plain states for flood forecasting and disaster mitigation. Developing hydrodynamic and hydrological models with sensor-based data will aid early warning. He also mentioned setting up of adequate rain gauges in hilly areas and regular monitoring through drones.
This expert said that to prevent the deterioration of the situation, it is necessary to urgently afforest the riverside areas through environmental management systems. Future flood disasters are expected to be greatly mitigated by economically viable and erosion-resistant tree planting and construction of water conservation infrastructure and conservation measures on land rights.