Continued impact of floods in many parts of India, following a season of relentless rainfall, and landslides has claimed many lives and displaced over four lakh people. When the Brahmaputra river enters the northeastern India from a region of high rainfall, it carries a large volume of water, breaching over embankments and submerging its flood plains, and ultimately converging with the Ganges into the Bay of Bengal.
The tapestry of these indelible imprints has been traced in the satellite data available on NASA’s LANCE, a world view real-time platform by our OSINT (Open Source Intelligence) team.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured the top image on September 3, 2023. The next image depicts the region submerged by the deluge.
Floodwaters vary in colour from blue to red, indicating severe flooding areas. The relentless downpour in the higher altitudes of North India has resulted in a surge in the water levels of numerous rivers that feed into the Brahmaputra, with several breaching the danger threshold, thereby posing a grave threat to the region.
Approximately 4 lakh people from eighteen districts – Barpeta, Biswanath, Chirang, Darrang, Dhemaji, Dhubri, Dibrugarh, Goalpara, Golaghat, Jorhat, Kamrup, Kamrup (Metro), Lakhimpur, Morigaon, Nagaon, Nalbari, Sivasagar, and Sonitpur of Assam have reportedly been affected.
A panoramic view of the Sentinel 1A SAR (Synthetic Aperture Radar) images of the Brahmaputra river extracted from Copernicus services – generated using an active system of recording microwave signals from the earth surface – shows a deeper deluge in contrast to the SAR image captured in May.
These false-colour images when joined together, show an extended stretch of the Brahmaputra river, which rolls across northeastern India en route to Bangladesh. Both images use a combination of infrared and visible light to increase the contrast between water and land.
In May to September, the Brahmaputra river once flowed through braided channels, but just a few months later, the channels could not be detected in the swollen river as floodwaters surged, affecting settlements along its banks, including cities, Tezpur and Guwahati.
Satellite images from the area near Mayong village in Assam show that the scanty river in June has now inflated to blanket an area over 17 kilometres across its floodplains.
Similarly, the region near Barpeta district also sees floodwaters inflating from about 12.5 kilometres initially to cover a region of approximately 17.3 km on both sides.
The Teesta river emerges in the eastern Himalayas, and flows through the Indian states of Sikkim and West Bengal to finally enter Bangladesh, converging with the Brahmaputra in the Rangpur division before it flows into the Bay of Bengal. The river can be seen in the satellite images of September 3, accessed from the Sentinel Hub in a flooded state.
Below the Teesta, the Brahmaputra splits into two distributary branches. The western branch, which contains the majority of the river’s floodwater flow, continues due south as the Jamuna to merge with the lower Ganges.
The cumulative rainfall till the month of August over Arunachal Pradesh shows an excess of 28 per cent over normal, as per the IMD.
While looking at the rain data for just the last week of August, Barpeta in Assam shows an excess of 212 per cent, Nalbari of 198 per cent, and Baksa of 212 per cent above the normal. In response to the crisis, 50 relief camps and centres have been opened to provide shelter and support. Among these, 7 are relief camps, while 43 serve as distribution points.
Very high precipitation during monsoon in the upper catchment areas resulted in severe flood inundation in the downslopes of the Brahmaputra basin, leading to floods in Bangladesh.
As per the Dhaka Times, the country has received 35.9 per cent excess rainfall than normal, in the month of August, causing short-term flooding in the river banks.
However, the Mymensingh and Khulna divisions remain in the normal rainfall category.
