Cyclone Rains Spur Papua New Guinea Landslides

NASA...

Sept. 24, 2025

April 20, 2026

A narrow, light-brown landslide scar cuts through dark green forested mountains in East New Britain and extends south toward a stream valley. Rivers swollen with floodwaters, areas of forest clearing, and scattered clouds are also visible in some parts of the image.

NASA Earth Observatory/Michala Garrison

Sept. 24, 2025

April 20, 2026

During a break in the clouds, the OLI (Operational Land Imager) on Landsat 9 captured an image of landslide fallout in the forested Gazelle district of East New Britain on April 20, 2026 (right). A second image from Landsat 9 shows the same area on September 24, 2025 (left), before the landslides.

Since much of Papua New Guinea lies close to the equator where the Coriolis effect is weak, the risk of tropical cyclones striking the island nation is relatively low, especially in its northern areas. Nevertheless, unusually warm sea surface temperatures and atmospheric conditions favorable to storm formation brought powerful Tropical Cyclone Maila dangerously close to the islands of Bougainville, New Britain, and New Ireland in April 2026, fueling intense rainfall.

The heavy rains saturated steep terrain in the Gazelle district of East New Britain, triggering landslides on and around April 9 that led to several deaths, according to news reports. The Landsat 9 satellite captured an image of the fresh landslide scars cutting through the dense tropical forests in the Baining Mountains on April 20, 2026. The Toriu River and other sediment-laden waterways are visible to the east of the landslides.

The landslides appear as light-brown swaths of exposed soil and debris extending north toward a nearby river valley, contrasting with the surrounding green vegetation and scattered white clouds. A second image from Landsat 9 shows the same area on September 24, 2025, before the landslides.

Maila was notable for its intensity—reaching Category 4 strength on Australia’s cyclone intensity scale (Category 3 on the Saffir-Simpson scale used for U.S. hurricanes)—and also for its slow movement near Papua New Guinea. Instead of passing quickly through the region, Maila lingered, allowing rainbands to repeatedly strike East New Britain. Satellite-based precipitation estimates from NASA’s Global Precipitation Measurement (GPM) mission indicate that hundreds of millimeters of rain likely fell across the region in less than a week.

NASA’s Landslide Hazard Assessment for Situational Awareness (LHASA) model uses precipitation estimates from GPM along with slope, soil, and land cover data to identify areas where rainfall is likely to trigger landslides. During the height of the storm, LHASA highlighted parts of East New Britain—including the Baining Mountains—as having an elevated risk of slope failure.

NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.