The evolution of gravity waves as they propagate into shallower water: a field experiment

This paper presents a small-scale field investigation into the evolution of surface gravity waves propagating above relatively steep bed slopes ([Formula: see text]) from deep waters to the shallowest threshold of intermediate water. The measurements were conducted at the Natural Ocean Engineering Laboratory (NOEL). The study analyzes diverse sea states to determine the influence of sea-state steepness and effective water depth ([Formula: see text]) on wave profiles and statistics. The results show a clear transition in wavefield properties: spectra narrow and peak in intermediate depths ([Formula: see text]) before significant energy dissipates in shallower water due to breaking ([Formula: see text]). While extreme waves in deeper water ([Formula: see text]) exhibit shapes consistent with quasi-determinism theory, wave profiles in shallow water ([Formula: see text]), evolve toward solitary wave trains, indicating a transition where frequency dispersion does not dominate the regime anymore. The analysis of wave height distributions shows that modern formulations perform robustly in intermediate depths, but all models struggle with the steepest, shallowest conditions where nonlinearity and breaking compete intensely.