Long Ship Waves in Shallow Water Bodies

Wakes from large high-speed ships frequently reveal many interesting and important features that are not present in the classical Kelvin ship wave system. Only a few differences are connected with the increase in the ship’s speed in a straightforward way. The majority of effects reflect nonlinear processes of wave generation and propagation. This overview concentrates on the recent results concerning the nature and consequences of these differences. The goal of the presentation is to highlight the new, nonlinear features of wakes from fast ferries, and the basic consequences of their presence for the safety of people and the environment in a comprehensive manner, but in terms understandable for non-experts. The starting point is the classical theory of the Kelvin wake and its modifications in shallow water. The pattern of ship waves undergoes major alterations when the ship’s speed becomes roughly equal with the maximum phase speed of linear waves for a given depth $\sqrt{gH}$ . At these speeds, qualitatively new structures such as groups of long, long-crested waves that resemble shallow-water solitons, and short monochromatic wave packets resembling envelope solitons may appear. These groups remain compact for a long time and considerably extend the area directly influenced by the ship traffic. Finally, we provide evidence of certain particular features of the impact of such waves in shallow areas and of possible ecological consequences of the increased hydrodynamic activity.