| 22 Jun 2026
The 2022 Rainfall-Triggered Landslide-Tsunami Disaster in Pilar, Abuyog, Leyte, Philippines and its implications for coastal hazard assessment
Abstract. On 12 April 2022, a rainfall-triggered landslide in Barangay Pilar, Abuyog, Leyte, Philippines generated destructive tsunamis upon reaching the coast, resulting in one of the deadliest landslide disasters in the country’s history. The event occurred during prolonged and intense rainfall associated with the interaction of a low pressure area, Severe Tropical Storm Megi (Agaton), and Typhoon Malakas (Basyang). The cascading rainfall–induced landslide–tsunami hazards caused 54 fatalities, injured 49 individuals, and left 33 persons missing and presumed dead, with tsunami inundation responsible for a substantial proportion of the losses. We reconstructed the event chronology and failure mechanisms using an integrated dataset comprising satellite imagery, unmanned aerial vehicle (UAV) surveys, field mapping, sedimentological analyses, and three-dimensional terrain modelling, eyewitness accounts, social media videos, and incident reports. Results indicate that two landslides with a total volume of around 5.5 x 105 m3 were mobilized as debris flows. The landslides were composed of volcanic materials that originated from a fault-controlled ridge south of Pilar that reached the coast of Leyte Gulf. The initial and larger debris flow generated tsunami waves with runup heights of about 12 m above sea level, devastating residential areas along the coast and overwhelming people fleeing the landslide. Analysis of landslide–tsunami coupling indicates that wave generation was governed primarily by high-momentum impact conditions, with debris flow velocities of up to 25 m/s and short source-to-shore distances limiting energy dissipation prior to coastal entry. These conditions produced strongly supercritical flow and demonstrate that relatively moderate-volume landslides can generate significant near-field tsunamis when velocity and proximity are favorable. This study is the first well-documented subaerial landslide-generated tsunami in the Philippines and provides a data-rich example of a rainfall-induced landslide–tsunami cascade in a tropical island setting. The Pilar disaster highlights the extreme hazard posed by rainfall-triggered landslides in steep coastal volcanic terrains and underscores the need to explicitly incorporate landslide–tsunami cascade scenarios into hazard assessment, early warning systems, and land-use planning in similar coastal regions.
Competing interests: Richard Ybanez is a PhD student of NHESS Executive Editor Dr. Bruce D. Malamud in the University of the Philippines National Institute of Geological Sciences. Dr. Alfredo Mahar Francisco A. Lagmay is the main supervisor of Mr. Ybañez in the same research. No other competing interest is known to the authors.
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