Relating Hydrodynamic Forcing and Topographic Response for Tide-Dominated Sandy Beaches

Abstract

To relate hydrodynamic forcing and topographic response for a tide-dominated sandy beach, extensive field measurements were carried out in the intertidal zone. Hydrodynamics and beach topography were monitored during a total of 12 weeks at two different study sites: one with a featureless intertidal zone and one with intertidal bars. The results of both study sites indicate that the intertidal beach grows when wave steepness is small, whereas it erodes when wave steepness is large. Spring-neap variations in tidal current direction heavily distort this trend: strong spring tidal currents transport sediment away from the beach, resulting in enhanced erosion. Tide-induced beach volume changes are on the same order of magnitude as wave-induced changes. Besides waves and tides, the effect of variations in the amount of sediment supply is substantial, with enhanced accretion when the sediment supply is large. The effect of variations in sediment supply on the intertidal beach topography is subordinate to the effect of waves and tide, though. From this study, it is concluded that larger waves are primarily erosive, but they can also enhance the natural sediment supply. Furthermore, it is found that tidal currents can be equally important as waves in shaping the beach topography, especially during spring tide on macrotidal beaches.

Morfologia e Sedimentação em Praias Oceânicas da Amazônia Oriental durante a Variação Anual de Chuvas

“…As forçantes marés e ventos são responsáveis por importantes mudanças morfológicas de praia, como a erosão das dunas anteriormente depositadas, durante os períodos de marés mais altas na estação chuvosa amazônica. Além disso, a maré pode desempenhar um papel importante no transporte destes sedimentos (Brand et al, 2020).…”

“…A morfodinâmica de praia está relacionada a interações complexas que envolvem descarga de ISSN:1984ISSN: -2295 Revista Brasileira de Geografia Física Homepage:https://periodicos.ufpe.br/revistas/rbgfe água e sedimentos de estuários, orientação de linha de costa, correntes costeiras, ondas, correntes das marés (Brand et al, 2020), que são as principais condicionantes da topografia e transporte de sedimentos em praias de macromarés (amplitude >4 m). A dinâmica complexa e variável, que caracteriza as contínuas alterações morfológicas e sedimentares em praiais, ocorre devido aos efeitos desta ampla quantidade de processos hidromorfodinâmicos.…”

ADV-Based Investigation on Bed Level Changes Over a Meso-Macro Tidal Beach

“…For meso-macro tidal and macro-tidal beaches, which are mainly featured with gentle beach slopes and dissipative beach states, the bed level changes were suppressed and were at the level of <5 cm for most of the cases over one tidal cycle, even after going through a storm surge event (Aagaard et al, 1998b;Anthony et al, 2004;Masselink et al, 2007;Puleo et al, 2014). Meanwhile, there tend to be no conspicuous patterns in the amplitudes of bed level changes for different tidal regimes (i.e., neap to spring tides), as larger bed level change amplitudes could occur during either spring or neap tides erratically (Brand et al, 2020). Specifically, the subdued bed level changes in response to large tide ranges were associated with larger morphological relaxation times caused by the small residence time of wave-related swash and surf zone processes on account of the larger horizontal tidal translation for mesomacro tidal beaches (Kroon and Masselink, 2002;Anthony et al, 2004;Reichmüth and Anthony, 2007).…”

“…For the studies about bed level changes concerning different geomorphic units over a meso-macro tidal beach, a portion of them focused on the measurement and prediction of intertidal bar evolution under different wave conditions (Vousdoukas et al, 2011;Ge et al, 2017;López-Dóriga and Ferreira, 2017;Brand et al, 2020), as the intertidal bar is a common feature of meso-macro tidal beaches, which are commonly short of other secondary morphological features such as beach cusps, low-tide terraces, skew bars, and rip morphology (Wright et al, 1987;Short, 1991;Masselink et al, 2007). Additionally, in recent years, more and more studies have attempted to distinguish the respective features of bed level changes within different wave zones (i.e., shoaling wave zone, surf zone, and swash zone).…”

Seasonal Variability On Cross-shore Profile in Meso-tidal Settings Due to Lunar Cycle Effects in Kuala Terengganu Coast

“…The lunar cycle can be characterized as the moon's changing phases, which affect various natural phenomena on the earth hydro-lithosphere, such as Earth's tides through gravitational forces. Prior research most likely predominately focused on the effect of "spring tide" towards coastal region, but not documented well on the implication in uence particularly during the phases Full Moon and New moon in meso-tidal settings (Brand et al, 2020; Leung Chee et al, 2014; Qian et al, 2019). During a Full or New Moon period, the forces exerted by the moon and the sun on the earth reinforce each other, resulting in the largest tidal range, known as 'spring tide'.…”