Typhoon Haiyan's sedimentary record in coastal environments of the Philippines and its palaeotempestological implications

Abstract

Abstract. On 8 November 2013, category 5 Supertyphoon Haiyan made landfall on the Philippines. During a post-typhoon survey in February 2014, Haiyan-related sand deposition and morphological changes were documented at four severely affected sites with different exposure to the typhoon track and different geological and geomorphological settings. Onshore sand sheets reaching 100–250 m inland are restricted to coastal areas with significant inundation due to amplification of surge levels in embayments or due to accompanying long-wave phenomena at the most exposed coastlines of Leyte and Samar. However, localized washover fans with a storm-typical laminated stratigraphy occurred even along coasts with limited inundation due to waves overtopping or breaching coastal barriers. On a recent reef platform off Negros in the Visayan Sea, storm waves entrained coral rubble from the reef slope and formed an intertidal coral ridge several hundreds of metres long when breaking at the reef edge. As these sediments and landforms were generated by one of the strongest storms ever recorded, they not only provide a recent reference for typhoon signatures that can be used for palaeotempestological and palaeotsunami studies in the region but might also increase the general spectrum of possible cyclone deposits. Although a rather atypical example for storm deposition due to the influence of infra-gravity waves, it nevertheless provides a valuable reference for an extreme case that should be considered when discriminating between storm and tsunami deposits in general. Even for sites with low topography and high inundation levels during Supertyphoon Haiyan, the landward extent of the documented sand sheets seems significantly smaller than typical sand sheets of large tsunamis. This criterion may potentially be used to distinguish both types of events.