The concept of wave base: fact and fiction

This study focusses on the processes that control the morphodynamics of the seabed in the shoaling wave domain, widely known as the shoreface. Shoreface morphodynamics is not only controlled by the local wave climate but also by associated wave- and wind-driven currents, the grain-size, and antecedent geomorphology. This paper provides basic information on sedimentological action of monochromatic waves at the seabed in the shoaling zone to the non-specialist without him-/herself having to solve the complex equations before arriving at workable solutions. It is emphasized that the traditional oceanographically defined wave base (0.5L₀) is not relevant in a geological/sedimentological context and should be replaced by a grain-size dependent effective wave base (EWB). Furthermore, open ocean swell-dominated shorefaces have to be distinguished from those of marginal seas dominated by local wind-generated waves. For convenience, a collection of tables and diagrams are provided in the electronic supplementary material (ESM) attached to this paper. They highlight the depths of effective wave bases for a range of grain sizes, wave heights and wave periods between 2 and 16 s.