Abstract
The displacement of a large amount of water in a moderate-sized estuary by a fast-moving mega-ship can generate tsunami-like waves. Such waves, generated by cruise ships, were observed in Tampa Bay, Florida, USA. Two distinct, long tsunami-like waves were measured, which were associated with the passage of a large cruise ship. The first wave had a period of 5.4 min and a height of 0.40 m near the shoreline. The second wave had a period of 2.5 min and was 0.23 m high. The peak velocity of the onshore flow during the second wave reached 0.65 m/s. The shorter, second wave propagated considerably faster than the first wave in the breaking zone. The measured wave celerity was less than 50% of the calculated values, using the shallow water approximation of the dispersion equation, suggesting that nonlinear effects play an important role. A fundamental similarity among the generation of tsunamis, as induced by mega-ships, landslides or earthquakes, is a process that causes a vertical velocity at the sea surface, where a freely propagating wave is produced. This mega-ship-generated tsunami provides a prototype field laboratory for systematically studying tsunami dynamics, particularly the strong turbulent flows associated with the breaking of a tsunami wave in the nearshore, and tsunami–land interactions. It also provides a realistic demonstration for public education, which is essential for the preparation and management of this unpreventable hazard.
Highlights
Tsunamis are among the deadliest and costliest natural hazards worldwide
The purpose of this paper is to provide a case study on the hydrodynamic conditions associated with breaking tsunami waves in the nearshore zone
The long waves generated by a fast-moving large cruise ship in an estuary (Upper Tampa Bay) bear significant similarities to tsunami waves and can be used as a prototype, physical model for systematic studies on the breaking of tsunami waves and tsunami–land interactions
Summary
Tsunamis are among the deadliest and costliest natural hazards worldwide. The risks can increase significantly in the future, as population density in coastal zones increases and sea-levels rise. The tremendous property damages and fatalities associated with tsunamis are mainly caused by the very strong flow associated with the breaking of the long wave, superimposed on the elevated and fast-rising water level [1,2] A tsunami is a series of waves generated by a sudden displacement of a large volume of water in the ocean. Common mechanisms inducing sudden large water displacement include earthquakes [4,5,6,7] and landslides [8,9,10,11]. The generation mechanisms for landslide-induced tsunamis are more diverse, spanning from impulsive waves due to subaerial landslides hitting the water with high-impact velocities [12] to submerged landslides moving farther at lower speeds [13,14]. Owing to the above complications, the nature and hazard posed by landslide tsunamis are not as well understood as those by earthquakes [9]
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