High Quality Content by WIKIPEDIA articles! In fluid dynamics, wave shoaling is the effect by which surface waves entering shallower water increase in wave height (which is about twice the amplitude). IT is caused by the fact that the group velocity, which is also the wave-energy transport velocity, decreases with water depth. UNder stationary conditions, this decrease in transport speed must be compensated by an increase in energy density. SHoaling waves will also exhibit a reduction in wavelength while the frequency remains constant. IN shallow water and parallel depth contours, non-breaking waves will increase in wave height as the wave packet enters shallower water. THis is particularly evident for tsunamis as they with devastating results wax in height when approaching a coastline.