Tsunami hazards pose significant threats to coastal communities, with wave amplification during shoaling being a critical factor in determining coastal impact. This study systematically investigates the influence of water depth on tsunami propagation and shoaling through a combination of idealized numerical flume experiments and realistic simulations for the Persian Gulf. The idealized configuration consists of a two-slope bathymetric profile representing the continental shelf and slope, with three depth scenarios (offshore depths of 2200 m, 1100 m, and 220 m) examined. The Persian Gulf case study evaluates tsunami propagation over real bathymetry and artificially deepened configurations (10× and 20× depth amplification) to assess the role of limited water depth on wave amplification.

Results from the idealized flume demonstrate that greater offshore depths produce more pronounced shoaling, with maximum wave heights of approximately 7 m, 5 m, and 3 m for the deep, intermediate, and shallow configurations, respectively. However, the shallowest configuration exhibits anomalous behavior where wave growth ceases and heights decrease due to breaking-induced dissipation, effectively limiting coastal amplification.

The Persian Gulf simulations reveal that while deeper configurations generally produce higher wave heights, a saturation effect exists beyond which additional depth increases yield diminishing returns. Notably, localized areas show complex responses where real-depth simulations produce comparable or higher waves than artificially deepened scenarios, highlighting the importance of site-specific bathymetric effects. These findings challenge the assumption that shallow marginal seas are inherently immune to significant tsunami hazards and emphasize the necessity of high-resolution, case-by-case assessments for accurate hazard evaluation in such regions.