Wave‐forced dynamics in the nearshore river mouths, and swash zones

Abstract

The role of wave forcing on the main hydro-morphological dynamics evolving in the shallow waters of the nearshore and at river mouths is analyzed. Focus is mainly on the cross-shore dynamics that evolve over mildly sloping barred, dissipative sandy beaches from the storm up to the yearly time scale, at most. Local and nonlocal mechanisms as well as connections across three main interrelated subsystems of the nearshore-the region of generation and evolution of nearshore bars, river mouths and the swash zoneare analyzed. The beach slope is a major controlling parameter for all nearshore dynamics. A local mechanism that must be properly described for a suitable representation of wave-forced dynamics of all such three subsystems is the proper correlation between orbital velocity and sediment concentration in the bottom boundary layer; while specific dynamics are the wave-current interaction and bar generation at river mouths and the sediment presuspension at the swash zone. Fundamental nonlocal mechanisms are both Infragravity (IG) waves and large-scale horizontal vortices (i.e. with vertical axes), both influencing the hydrodynamics, the sediment transport and the seabed morphology across the whole nearshore. Major connections across the three subsystems are the upriver This article is protected by copyright. All rights reserved. This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/esp.4699 propagation of IG waves generated by breaking sea waves and swash-swash interactions, the interplay between the swash zone and along-river-flank sediment transport and the evolution of nearshore sand bars.

Sandbar dynamics in microtidal environments: Migration patterns in unprotected and bounded beaches

“…Some conceptual models have been proposed to describe the morphology and behaviour of sandbars [23]. In the widely recognized Net O shore Migration (NOM) model, a sand bar undergoes a three-stage cycle often spanning years to decades.…”

Wave-Forced Dynamics at Microtidal River Mouths

“…Although the influence of classical riverine and marine hydrodynamic forcing mechanisms, such as gravity waves and tides, are typically accounted for to describe the estuarine dynamics, an increasing number of studies is focusing on infragravity (IG hereafter) waves, which are seen to play a non-negligible role in estuary evolution [5]. IG waves are a specific type of low-frequency waves with periods between 20 and 30 seconds to 5 minutes, larger than those of sea/swell waves [6,7].…”

River Plume Modulation by Infragravity Wave Forcing

“…The effects of infragravity (hereafter IG) motions are not considered in the above formulations. Infragravity waves, while small offshore, have been shown to influence the hydrodynamics and morphodynamics of beaches, small tidal inlets and estuaries (Bertin et al., 2019; Bertin & Olabarrieta, 2016; Brocchini, 2020; Elgar et al., 1992; McSweeney et al., 2020; Melito et al., 2020; Mendes et al., 2020; Williams & Stacey, 2016). IG waves result in surface water level fluctuations with periods of 30–300 s that are typically associated with wave groups and result from nonlinear interactions in the incident short waves (Bertin et al., 2018; Henderson et al., 2006; Schäffer, 1993).…”