Laboratory experiments on the evolution of a submerged berm driven by low-energy irregular waves.

A reduced-scale mobile-bed model is employed in a series of flume experiments to investigate the evolution of a submerged berm under low-energy irregular waves. Sixteen flume tests are conducted on the same submerged berm model under different wave conditions, and the bed elevations and water surface elevations are recorded along the profile during the tests. The results are analyzed comprehensively and compared to those under regular wave conditions from a previous study. Generally, no bulk evolution of the submerged berm is observed, and large wave periods lead to wavy profile shape and offshore sediment transport. The wavy profile can be found under both regular and irregular wave conditions, while the offshore transport is only observed under irregular wave conditions. Two major evolution patterns are extracted with the Empirical Orthogonal Function (EOF) analysis, including the decrease of the crest elevation and offshore sediment transport to the seaward-side slope, both of which are impacted to a larger degree by wave period than wave height. A cross-shore analysis is conducted on the wave hydrodynamic parameters and sediment transport parameters, based on which the differences in the evolution of the submerged berm under small and large wave periods are explained. This paper proposes new insights on the evolution of submerged berms under low-energy irregular waves and provides a new perspective to explain different behaviors of submerged berms via a comparison with the test results under low-energy regular waves from previous studies. • The evolution of a submerged berm under low-energy irregular waves are studied via a series of flume tests. • The behaviors of the submerged berm under irregular wave and regular wave conditions are compared. • Large wave period leads to offshore sediment transport under low-energy irregular waves. • The submerged berm exhibits two major evolution patterns: a crest elevation decrease and the offshore sediment transport. • The variations in cross-shore H s , Sk v and Sk a account for the differences in the evolution of the submerged berm. [ABSTRACT FROM AUTHOR]