Tsunami Waveform and Velocity Characteristics over Sloping Bathymetry: Pressure Tank-Based Wave Flume Experiments

Abstract

Since the 2004 Aceh Tsunami, researchers have recognized that tsunami disasters represent a significant and real threat that must be carefully considered. As tsunami waves propagate from deep to shallow waters, they undergo hydrodynamic transformations, including shoaling and wave steepening. In this study, a series laboratory experiments were conducted in a tsunami wave flume to investigate the evolution of tsunami waves and their interaction with sloping bathymetry. The experiments were performed in a 60m long, 2.5m wide, and 1.7m high flume operated by TDMRC-USK, Banda Aceh. Tsunami-like waves were generated using a computer-controlled pneumatic pressure tank manufactured by HR Wallingford, United Kingdom. Free-surface elevation and velocity were recorded at multiple gauges positioned along the flume. Results indicate that more than 88% of the variability in tsunami arrival time is explained by propagation distance, demonstrating a strong distance-arrival time relationship. Measured velocities increase over the 1:4 slope due to shoaling and wave breaking. Wave amplitude gradually increases from WG1-WG3 as the wave propagates toward shallower water, resulting in progressive wave energy concentration due to shoaling. After wave breaking at WG4, the wave amplitude progressively attenuates toward WG7 along the 1:28 slope and horizontal, reflecting substantial wave energy dissipation during subsequent propagation.