Sediment-Wave Parametric Characterization of Beaches

Abstract

Sediment-wave parameters, notably the parameter Ω = H_b/W_sT (where H_b, is wave breaker height, W_s sediment fall velocity, and T wave period), have been used in the literature to identify thresholds between various beach morphodynamic states ranging from reflective, through intermediate, to dissipative. Such parameters may be useful as elementary descriptors of beaches, especially in microtidal swell wave settings with mature sediment suites, and when used in conjunction with conceptual beach state models elaborated in recent years. Although the problems of temporal wave height variability and large tide ranges have been addressed in the parametric characterization of various beach types, these factors, together with sediment variability, may result in beach morphodynamic systems that cannot be meaningfully characterized by sediment-wave parameters. Morphodynamic parameters such as the Iribarren Number ξ_b (ξ_b = tan_b/ (H_b/L_o)^0.5,  where tan_b represents beach slope, H_b, is wave breaker height, and L_o deepwater wavelength), and the surf-scaling parameter ϵ (ϵ = a_bw²/(gtan²b), where a_b, is runup amplitude on the beach, w wave radian frequency, and g the gravitational constant), are based on beach slope, and avoid the problem of the choice of representative beach sediment parameters. The intertidal beach slope is also a better index of characterization of spatial and temporal changes in the reflective-to-dissipative beach morphodynamic continuum, especially in settings with large tide ranges.