EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-5978 Brief communication: Tidal timing and minutes to act during the 15 August 2026 Flores tsunami Iwantoro Arya https://orcid.org/0000-0002-5544-2530 1 Harahap Rima https://orcid.org/0009-0004-7695-8191 1 2 Boulton Sarah https://orcid.org/0000-0002-8251-0025 3 Masselink Gerd 1 Centre for Coastal and Ocean Processes and Engineering (C-COPE), University of Plymouth, Plymouth, PL4 8AA, UK Ocean Engineering Department, Kalimantan Institute of Technology, Balikpapan, 76127, Indonesia Centre for Research in Natural Hazards and Risk Reduction (CHaRR), University of Plymouth, Plymouth, PL4 8AA, UK 12 11 2026 2026 1 16 Copyright: © 2026 Arya Iwantoro et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5978/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5978/egusphere-2026-5978.pdf

The 15 August 2026 Flores tsunami provides a case for evaluating how tidal timing can alter inundation. We reconstruct the event with coupled Delft3D-SFINCS simulations constrained by post-event observations. We then simulate the same tsunami at high tide (+0.7 m relative to mean sea level, MSL), representing the spring high tide recorded on the event day. Relative to the 3.81 km<sup>2</sup> reconstructed-event inundation above highest astronomical tide (HAT), high tide increases inundated area to 11.84 km<sup>2</sup>, a 3.1-fold increase. These results support tide-informed hazard maps, evacuation planning, community education, and preparedness close to tsunami sources.

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