NASA images show Gandak River flooding as Bihar reports more embankment breaches

NASA’s Earth Observatory reported on October 2 that satellite images showed the Gandak River widening across parts of Nepal and India after late September rain. A gauge in Nepal reached its highest recorded level, while separate reports from Bihar described flooded villages, damaged crops and new embankment breaches. The images show the spread of water; the accounts from Bihar describe its effects on communities downstream.

NASA compared images captured on September 20 and September 29 by instruments aboard its Terra and Aqua satellites. In the later image, the river appears much wider. NASA said runoff from torrential rain had entered the Gandak’s braided channel and that water overtopped or breached embankments in several areas, inundating farmland and settlements along hundreds of kilometres.

What NASA’s Gandak River images show

The images use false colour to make floodwater easier to distinguish: water appears blue, vegetation bright green and clouds light blue. They show where water had spread at the time of the September 29 observation, compared with the September 20 view. NASA identified flooding in parts of Bagaha, Areraj and Fulia Khand, including settled areas.

NASA also distinguished between water covering seasonal fields on low-lying sand and silt deposits within the river channel, where flooding is expected, and water extending beyond embankments into settled places. That distinction matters when reading the images: a wider blue channel alone does not establish the number of homes affected or the scale of losses. NASA said authorities were still assessing the damage.

Where the Gandak reached record levels

NASA cited data from Nepal’s Department of Hydrology and Meteorology showing that the gauge at Devghat reached 11.94 metres on September 27. It described that as the highest reading there since measurements began in the 1960s. The figure is a reading at one Nepalese gauge, not a measurement for the whole river or for any station in Bihar.

NASA also said news reports identified new high-water marks at four Indian gauges: Bagaha, Dumariaghat, Rewaghat and Lalganj. Its account did not give the readings at those stations. The reported Indian records therefore add locations to the picture of the flood, but the 11.94-metre Devghat figure should not be applied to them.

How flooding affected communities in Bihar

Reporting from Bihar describes what the satellite comparison cannot measure on its own. On September 30, The New Indian Express reported that Chief Minister Samrat Choudhary surveyed flood-affected areas in West Champaran and Saran from the air. He also visited a relief centre in Bathna, where he reviewed arrangements for food, medical care, drinking water, sanitation, accommodation and livestock.

The New Indian Express cited water-resources officials on an approximately six-metre breach near Sheetalpur in Gopalganj on September 30. It also reported that an approximately eight-metre section of the right Saran embankment near Haizalpur had subsided overnight, allowing water into nearby areas. Officials warned that low-lying villages near the breaches could be inundated and that connections could be disrupted.

By October 1, The Times of India reported two more breaches in Saran and Muzaffarpur. It said more than 200 villages had been inundated, with standing paddy and other kharif crops damaged, and identified six Gandak-basin districts under close watch: West Champaran, East Champaran, Gopalganj, Muzaffarpur, Saran and Vaishali. Those figures describe the situation reported at that point, rather than a final damage assessment.

Relief operations and remaining uncertainties

The Times of India reported that two Indian Air Force helicopter sorties dropped dry-ration packets to flood-affected people in Panapur block of Saran. The supplies included gram, sattu, flattened rice, sugar and oral rehydration salts. The newspaper also reported floodwater overtopping sections of the Muzaffarpur–Chapra highway, showing that the disruption extended beyond fields and riverbank settlements.

In West Champaran, farmers sought prompt assessments and compensation for crop and other damage, according to The Times of India. NASA said reports indicated that hundreds of villages and thousands of people had been affected or displaced, while authorities continued to assess the full extent of the damage. The available accounts do not establish final losses or when flood conditions will recede.