Ship-induced solitary Riemann waves of depression in Venice Lagoon

• Unprecedently deep long-living ship-induced waves of depression detected.
• Such waves are generated in channels with side banks under low Froude numbers.
• The propagation of these waves is replicated using Riemann waves.
• Long-living waves of depression form bore-like features at rear slope.

We demonstrate that ships of moderate size, sailing at low depth Froude numbers (0.37–0.5) in a navigation channel surrounded by shallow banks, produce depressions with depths up to 2.5 m. These depressions (Bernoulli wakes) propagate as long-living strongly nonlinear solitary Riemann waves of depression substantial distances into Venice Lagoon. They gradually become strongly asymmetric with the rear of the depression becoming extremely steep, similar to a bore. As they are dynamically similar, air pressure fluctuations moving over variable-depth coastal areas could generate meteorological tsunamis with a leading depression wave followed by a devastating bore-like feature.