Stoil Chapkanski, Gilles Brocard, Franck Lavigne, Tomy Afrizal, Ella Meilianda, Nazli Ismail, Jędrzej Majewski, Patrick Daly, Benjamin Horton, Adam Switzer, Annika Steuer, Bernhard Siemon, Darusman Darusman, Clément Virmoux, Jean-Philippe Goiran
The Aceh River delta, northern Sumatra, is a subject of interest since the coastline was struck, more than any other, by the 2004 Indian Ocean Tsunami, the largest recorded in human history. Thereafter, significant scientific efforts focused on short-term dynamics to address the environmental effects of the tsunami, but the long-term evolution of the delta in this specific context of volcanic eruptions, megathrust earthquakes and tsunami landing, however, remains to be understood. This study investigates the subaerial delta, based on shallow sediment borehole stratigraphies and C14 ages, in order to provide a partial reconstruction of the western and eastern fluvial and coastal evolution over the past 7 ky. It also benefits from comprehensive resistivity maps produced during recent helicopter-borne electromagnetic (HEM) surveys, and from earlier geomorphological mapping. By prograding, the delta expanded seaward, exposure to swell increased, and a large strandplain accreted along the eastern delta front from 4 to 1 ky BCE. The delta thus evolved asymmetrically, with higher, tightly-stacked beach ridges in the east, which accreted at ∼6 km2/ky. Meanwhile, the Aceh River remained stable, along the western side of the delta, burying the western strandplain under its floodplain. After 0.5 ky BCE, delta progradation increased to ∼14 km2/ky, generating low-lying and wider spaced beach ridges to the east. A series of river avulsions between 0.2 ky BCE and 1.6 ky CE shifted the river course from the west to the center of the delta. An asymmetric cuspate promontory grew at 23 km2/ky after 0.5 ky in front of the current mouth of the river, projecting 1 km offshore of the current coastline, before undergoing erosion in the past few centuries. Here, we discuss which combination of global and local factors, including sea level change, sediment supply, wave climate, tectonics, land use and tsunamis may explain the most salient processes during the growth of the Aceh River delta. Beyond its local interest, this study provides clues for a wider understanding of the complexity of subaerial delta development. © 2025 The Authors
University of Rouen Normandy, IDEES Laboratory, UMR 6266, CNRS, 17 Rue Lavoisier, Mont Saint-Aignan, 76821, France; University Paris 1, Panthéon-Sorbonne-Laboratory of Physical Geography (LGP), UMR 8591, CNRS, 2 Rue Henri Dunant, Thiais, 94320, France; Archéorient, UMR 5133, University of Lyon 2-CNRS, 7 rue Raulin, Lyon, 69007, France; of Mathematics and Applied Science, Syiah Kuala University, Banda Aceh, 23111, Indonesia; Tsunami and Disaster Mitigation Research Center (TDMRC), Universitas Syiah Kuala, Banda Aceh, 23233, Indonesia; Department of Geophysics, Syiah Kuala University, Banda Aceh, 23111, Indonesia; Geohazards Research Unit, Institute of Geology, Adam Mickiewicz University, Ul. Bogumiła Krygowskiego 12, Poznań, 61-680, Poland; Earth Observatory of Singapore, Nanyang Technological University, 50 Nanyang Av, Block N2-01a-15, 639798, Singapore; School of Energy and Environment, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong; Federal Institute for Geosciences and Natural Resources (BGR), Stilleweg 2, Hannover, D-30655, Germany; Post-Graduate School, Universitas Syiah Kuala, Banda Aceh, 23111, Indonesia
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