Rains Swamp the Gandak River

Between September 24 and 27, 2026, torrential rains drenched Nepal’s mountainous Lumbini and Gandaki provinces. The late-monsoon deluge triggered landslides and pushed the Gandak River, also called the Narayani, to record levels in both Nepal and India. Runoff streaming into the braided river system overtopped and breached embankments in several areas, inundating farmland and settlements along the river for hundreds of kilometers. News reports indicated that flooding and landslides affected hundreds of villages and displaced thousands of people.

NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer) instruments on the Terra and Aqua satellites captured images on September 20 and September 29, 2026, showing the extent of the flooding. The false-color images combine infrared and visible light (MODIS bands 7-2-1) to make it easier to distinguish water: floodwater appears blue, vegetation is bright green, and clouds are light blue.

In many areas, water inundated seasonal fields on low-lying deposits of sand and silt within the river’s channel, called diara, where flooding is expected. However, it also breached embankments and flooded several settled areas, including parts of Bagaha, Areraj, and Fulia Khand. Data from Nepal’s Department of Hydrology and Meteorology indicated that a gauge in Devghāṭ reached as high as 11.94 meters on September 27, the highest since measurements began there in the 1960s. According to news reports, gauges in India along the Gandak that set new high-water marks included Bagaha, Dumariaghat, Rewaghat, and Lalganj.

As authorities assessed the full extent of the damage, NASA noted several tools and datasets available for tracking rainfall and flooding, including Worldview, FLOOD Viewer, and the GPM IMERG Global Viewer. The Earth Observatory images were created by Lauren Dauphin using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview, with the story by Adam Voiland.