Investigating historical storm surge occurrences in the Philippines from tide gauge observations

Abstract

Tropical cyclones frequently affect the Philippines, making its coastal areas highly vulnerable to storm surges. As an archipelagic country with an extensive and complex coastline, local coastal characteristics strongly influence surge magnitude and extent. However, most previous studies have focused on individual extreme events or numerical simulations of specific TCs, with few systematically reconstructing historical storm surges from instrumental observations nationwide. This study fills this gap by investigating historical storm surge events (SSEs) using tide gauge observations from 1947 to 2024. An annually varying threshold was applied to residual sea levels derived from de-tided water levels, identifying 133 SSEs across multiple coastal locations. Most storm surges measured 20–50 cm, whereas only about 5% exceeded 1 m. In contrast, storm tides (the combination of storm surge and astronomical tide), exceeded 1 m in approximately 39% of events, demonstrating the important contribution of tidal timing to coastal water levels. The highest storm surge, 211 cm, was recorded at Pasacao, Camarines Sur during Typhoon Molave (2020). High storm surges mainly occurred along the coasts of Catanduanes, Camarines Sur, Eastern Samar, Cagayan, Batanes, and Palawan, where shallow and wide continental shelves favor surge amplification, while they were largely absent in Mindanao. Case studies of Typhoon Molave (2020) and Super Typhoon Goni (2020) further highlighted the influence of coastline orientation and tidal phase on storm surge impacts. The resulting database represents the most comprehensive instrument-based storm surge inventory for the Philippines to date and provides a valuable resource for storm surge forecasting, hazard assessment, and model validation.