Typhoon Haiyan Overwash Sediments From Leyte Gulf Coastlines Show Local Spatial Variations With Hybrid Storm and Tsunami Signatures

Marine inundation associated with the 5 to 8 m storm surge of Typhoon Haiyan in 2013 left overwash sediments inland on the coastal plains of the northwestern shores of Leyte Gulf, Philippines. The Haiyan overwash deposit provides a modern sedimentary record of storm surge deposition from a Category 5 landfalling typhoon. We studied overwash sediments at two locations that experienced similar storm surge conditions but represent contrasting sedimentological regimes, namely a siliciclastic coast and a mixed siliciclastic-carbonate coast. The contrasting local geology is significantly reflected in the differences in sediment grain size, composition and sorting at the two sites. The Haiyan overwash sediments are predominantly sand and silt and can be traced up to ~ 1.6 km inland, extending farther beyond the previously reported \u3c 300 m inland limit of sedimentation. Sites with similar geology, topographic relief, and overland flow conditions show significant spatial variability of sediment thickness and inland extent. We infer that other local factors such as small-scale variations in topography and the type of vegetation covermight influence the spatial distribution of overwash sediments. The Haiyan overwash deposits exhibit planar stratification, a coarsening upward sequence, a non-systematic landward fining trend, and a sharp depositional (rarely erosional) basal contact with the underlying substrate. Overall, the Haiyan deposits have sedimentologic and stratigraphic characteristics that show a hybrid signature common to both storm and tsunami deposits

Micropaleontology of the 2013 Typhoon Haiyan Overwash Sediments from the Leyte Gulf, Philippines

Coastal geologic records allow for the assessment of long-term patterns of tropical cyclone variability. However, the accuracy of geologic reconstructions of tropical cyclones is limited by the lack of modern analogues. We describe the microfossil (foraminifera and testate amoebae) assemblages contained within overwash sediments deposited by Typhoon Haiyan when it made landfall on the islands of Leyte and Samar in the Philippines on 7 November 2013 as a Category 5 super typhoon. The overwash sediments were transported up to 1.7 km inland at four study sites. The sediments consisted of light brown medium sand in a layer \u3c1 to 8 cm thick. We used Partitioning Around a Medoid (PAM) cluster analysis to identify lateral and vertical changes in the foraminiferal and testate amoebae data. The presence of intertidal and subtidal benthic, and planktic foraminifera that were variably unaltered and abraded identify the microfossil signature of the overwash sediments. Agglutinated mangrove foraminifera and testate amoebae were present within the overwash sediments at many locations and indicate terrestrial scouring by Haiyan\u27s storm surge. PAM cluster analysis subdivided the Haiyan microfossil dataset into two assemblages based on depositional environment: (1) a low-energy mixed-carbonate tidal flat located on Samar Island (Basey transect); and (2) a higher-energy clastic coastline near Tanauan on Leyte Island (Santa Cruz, Solano, and Magay transects). The assemblages and the taphonomy suggest a mixed provenance, including intertidal and subtidal sources, as well as a contribution of sediment sourced from deeper water and terrestrial environments. (C) 2016 Elsevier B.V. All rights reserved

Geomorphic and sedimentologic imprints of typhoons Durian and Haiyan storm surges on the Philippine coasts

Typhoon Haiyan tragically attests to the vulnerability of Philippine coasts to storm surge hazard. It has also highlighted the limited and patchy knowledge that exists on the impacts to immediately affected communities despite the high frequency of storm surges in the archipelago. Moving forward, this dissertation contributes to increasing the level of local and regional science-based knowledge by laying down groundwork on the geologic investigations of storm surge impacts in the Philippines. Two recent storm events namely the 2006 Typhoon Durian (Reming) and the 2013 Typhoon Haiyan (Yolanda) provided an opportunity to study the geomorphic and sedimentologic imprints of storm surges and the resulting coastal overwash. This dissertation though primarily built upon a geological framework of storm surge has benefited considerably from the integration of multiple disciplines including meteorology, oceanography, coastal engineering, and history. Overall, the multi-disciplinary approach led to (1) local understanding of storm surge dynamics and the factors affecting the spatial variation of amplification leading to inundation overland; (2) characterization of the onshore geomorphic and sediment imprints within the bounds of hydrodynamic conditions and sediment transport processes; and (3) historically oriented investigation of storm surge heights and the geologic impacts to the coasts near typhoon landfalls in the Philippines.​Doctor of Philosophy (ASE

Geomorphological and sedimentological records of recent storms on a volcaniclastic coast in Bicol, Philippines

Typhoon Durian in November 2006 was most notable for a series of devastating lahars that buried communities at the base of Mayon volcano in Bicol, Philippines. Typhoon Durian delivered extreme rainfall that remobilized volcanic debris that caused more than-1200 deaths and extensive property damage. Although not as deadly as the lahar, Typhoon Durian also generated a storm surge that caused localized dune breaching on Malinao barrier sand spit in Lagonoy Gulf. In the absence of instrumental data of the storm surge, we used the geomorphical and sedimentary imprints including erosion scarps, washover fans and terraces to infer the inundation heights on the barrier spit. The surface elevations of washover fans, terraces and relic dunes indicate inundation heights above 1.5 m but not exceeding 3 m. Typhoon Durian's overwash deposit is characterized by typical washover fan stratigraphy, and exhibits horizontal to sub-horizontal lamination on the front to mid-fan and foreset stratification near the fan terminus. Subsurface stratigraphy using shore-normal ground penetrating radar (GPR) imaging reveals at least two buried erosional surfaces farther inland from the erosional surface of Typhoon Durian. Similar to Durian, the older erosional surfaces were probably sustained from previous typhoons. We infer that episodic erosional events most likely have repeatedly disrupted the prograding development of the Malinao barrier spit. Typhoon Durian highlights the exposure of volcanic landscapes to multiple hazards from cyclone landfall. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)

Typhoon Haiyan overwash sediments from Leyte Gulf coastlines show local spatial variations with hybrid storm and tsunami signatures

Marine inundation associated with the 5 to 8 m storm surge of Typhoon Haiyan in 2013 left overwash sediments inland on the coastal plains of the northwestern shores of Leyte Gulf, Philippines. The Haiyan overwash deposit provides a modern sedimentary record of storm surge deposition from a Category 5 landfalling typhoon. We studied overwash sediments at two locations that experienced similar storm surge conditions but represent contrasting sedimentological regimes, namely a siliciclastic coast and a mixed siliciclastic-carbonate coast. The contrasting local geology is significantly reflected in the differences in sediment grain size, composition and sorting at the two sites. The Haiyan overwash sediments are predominantly sand and silt and can be traced up to ~ 1.6 km inland, extending farther beyond the previously reported < 300 m inland limit of sedimentation. Sites with similar geology, topographic relief, and overland flow conditions show significant spatial variability of sediment thickness and inland extent. We infer that other local factors such as small-scale variations in topography and the type of vegetation cover might influence the spatial distribution of overwash sediments. The Haiyan overwash deposits exhibit planar stratification, a coarsening upward sequence, a non-systematic landward fining trend, and a sharp depositional (rarely erosional) basal contact with the underlying substrate. Overall, the Haiyan deposits have sedimentologic and stratigraphic characteristics that show a hybrid signature common to both storm and tsunami deposits.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio

Ground Penetrating Radar (GPR) Survey of Ground penetrating radar (GPR) survey of formerly mined coastal sand in central Vietnam: a rapid, non-invasive method for investigating the extent and impact of Mined Areas

Ground Penetrating Radar (GPR) offers a non-invasive, high-resolution subsurface imaging method that can be used to investigate and characterise the sedimentary features and depositional history of various coastal deposits. GPR utilises the electromagnetic wave properties in the megahertz frequency range and can generate 2D and 3D images of the subsurface to identify coastal depositional features to a depth in excess of 20m. In this study we use a series of GPR surveys to identify the depth and physical characteristics of an infilled site formerly subject to sand mining for heavy mineral sands. We outline a fast non-invasive technique that allows large areas of coastal dunes to be imaged for the purposes of delineating past land uses. The technique is likely to be particularly applicable to developing coasts where the historical record is incomplete or fragmentary or there has been a history of poorly constrained or illegal sand mining

Dimension anthropique de l'éruption du Mont Pinatubo (Philippines) entre 800 et 500 ans BP

International audienceLe volcan Pinatubo, aux Philippines, est célèbre pour son réveil brutal en 1991. Beaucoup moins connue est l'éruption précédente qui eu lieu entre 800 et 500 ans BP. La connaissance des conséquences de cet événement a récemment progressé avec la découverte de sites archéologiques et l'étude de témoignages oraux et géographiques. Des fouilles ont permis d'établir que des coulées pyroclastiques et des lahars ont probablement conduit à l'abandon d'importants villages situés sur les piémonts du volcan. Sur le versant est, la localisation des sites archéologiques et un certain nombre de toponymesactuels suggère une redistribution générale de la population vers de nouvelles terres côtières remblayées par des dépôts de lahars. Ce redéploiement démographique ne s'est pas produit sur le versant ouest malgré de similaires remblaiements côtiers. Ces modifications topographiques et sociodémographiques ont profondément perturbé le contexte économique et notamment les activités commerciales qui liaient alors la région au continent asiatique. Les témoignages oraux de l'éruption duMt. Pinatubo entre 800 et 500 ans BP, notamment des légendes, nous renseignent quant à eux sur les groupes ethnolinguistiques affectés par cette catastrophe (aetas, kapampangans et sambals). La connaissance de ces événements passés s'avère importante afin d'anticiper de futures catastrophes

Surf beat-induced overwash during Typhoon Haiyan deposited two distinct sediment assemblages on the carbonate coast of Hernani, Samar, central Philippines

Wave set-up steepened and accentuated the storm surge during Typhoon Haiyan in November 2013 resulting in bore-like flooding with surge heights of 7 m and flow velocities reaching 5 m s on the open-sea coastal plain near Hernani. This study investigates two distinct sediment assemblages left behind by the coastal flooding associated with this surge. The first assemblage consists of numerous coastal boulders that now occupy the reef flat, and the second pertains to a laterally extensive sand sheet that blanketed the coastal plain up to ~ 300 m inland. The majority of the boulders has b axes between 1 and 2 m, weigh no > 10 t, and were originally submerged on the reef edge. The boulders found more landwards of the reef edge were potentially lying loosely on the reef flat prior to Haiyan. In contrast, the coarse carbonate sand sheet starts at ~ 10 m inland of the current shoreline and has a maximum thickness of 10 cm and gradually thins to 3 mm at ~ 300 m inland. The Haiyan sand contains moderate concentrations of foraminifera (Amphistegina spp., Baculogypsina sphaerulata, and Peneroplis spp.) that were both abraded and unaltered, pointing to a reef flat and beach source for the sand. Sediment transport inverse modeling complements previous flow velocity estimates using numerical modeling, which altogether indicate sustained high-velocity overland flow despite the presence of coral reefs and mangroves as natural defenses to extreme waves