Morphology of a Low-Energy Beach, Como Beach, Western Australia

Eliot, Matt; Travers, Ailbhe; Eliot, Ian

doi:10.2112/05a-0006.1

Cited by 37 publications

(12 citation statements)

References 21 publications

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“…Type (3): Low‐Energy Finger Bars. These transverse bars (Figure c) are persistent features in fetch‐limited beaches without a shore‐parallel bar [ Falqués , ; Bruner and Smosna , ; Eliot et al , ; Pellón et al , ]. Only Bruner and Smosna [] and Pellón et al [] gave information concerning both their orientation and the forcing direction.…”

Section: Transverse Barsmentioning

confidence: 99%

Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration

Ribas

Falqués

Swart

et al. 2015

Reviews of Geophysics

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This review highlights the important role of the depth‐averaged sediment concentration (DASC) to understand the formation of a number of coastal morphodynamic features that have an alongshore rhythmic pattern: beach cusps, surf zone transverse and crescentic bars, and shoreface‐connected sand ridges. We present a formulation and methodology, based on the knowledge of the DASC (which equals the sediment load divided by the water depth), that has been successfully used to understand the characteristics of these features. These sand bodies, relevant for coastal engineering and other disciplines, are located in different parts of the coastal zone and are characterized by different spatial and temporal scales, but the same technique can be used to understand them. Since the sand bodies occur in the presence of depth‐averaged currents, the sediment transport approximately equals a sediment load times the current. Moreover, it is assumed that waves essentially mobilize the sediment, and the current increases this mobilization and advects the sediment. In such conditions, knowing the spatial distribution of the DASC and the depth‐averaged currents induced by the forcing (waves, wind, and pressure gradients) over the patterns allows inferring the convergence/divergence of sediment transport. Deposition (erosion) occurs where the current flows from areas of high to low (low to high) values of DASC. The formulation and methodology are especially useful to understand the positive feedback mechanisms between flow and morphology leading to the formation of those morphological features, but the physical mechanisms for their migration, their finite‐amplitude behavior and their decay can also be explored.

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Section: Transverse Barsmentioning

confidence: 99%

Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration

Ribas

Falqués

Swart

et al. 2015

Reviews of Geophysics

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“…Estuarine and bay coasts are widespread and densely populated (Eliot et al, 2006;Vila-Concejo et al, 2010;Harris et al, 2020). A ubiquitous feature of estuaries and bays is sandy beaches (Vila-Concejo et al, 2020), which can be small in scale when compared with open coast beaches.…”

Section: Introductionmentioning

confidence: 99%

“…Classifications and conceptual models that are routinely applied to sandy wave-dominated open coast beaches such as Wright and Short (1984) are based largely on features such as breaker bars and rip channels that generally do not occur on BEBs (Jackson et al, 2002). The works of Hegge et al (1996), Eliot et al (2006) and Travers et al (2010) provide an understanding of the morphology of low-energy microtidal beaches sheltered by reefs, islands and headlands in south-western Australia. Meanwhile, Nordstrom (1980), Nordstrom et al (1990), Jackson and Nordstrom (1992) and Nordstrom et al (1996), among other works such as Rosen (1977) and Rosen (1980), focused largely on beaches in estuaries and bays in north-eastern USA.…”

Section: Introductionmentioning

confidence: 99%

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

Gallop

Vila‐Concejo

Fellowes

et al. 2020

Earth Surf Processes Landf

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Many estuaries contain sandy beaches that provide habitats and offer protective buffers for wetlands and infrastructure, alongside cultural and recreational resources. Research underpinning coastal management tends to focus on tide‐ and swell‐dominated sandy beaches, but little attention is given to beaches in estuaries and bays (BEBs) that exist along a continuum of wind/swell wave, tide and riverine influence. BEBs are subject to less wave energy than open coast locations because of the generally narrow window of directions for which ocean waves can propagate through the entrance. However, when storm wave direction coincides with the orientation of the estuary or bay entrance, waves can penetrate several kilometres inside. Here we focus on eight BEBs in two major bays/estuaries in Sydney, Australia and present observations from before and after a major extratropical storm with waves from an atypical direction in June 2016. We quantify magnitudes of beach erosion and recovery rates for 3 years post‐storm. We show that when high‐energy storm waves penetrate bays and estuaries, BEBs can undergo up to 100% of subaerial beach erosion. Three years after the storm, only 5 of the 29 (17%) eroded subaerial beach profiles had recovered to their pre‐storm volume. This is likely due to the lack of low‐frequency, beach‐building waves at BEBs under modal weather conditions in between storms, in contrast to open coast beaches. We also show that the recovery of BEBs may be limited by the absence of adjacent sediment reservoirs due to the dominance of tidal processes mid‐channel. Our study highlights the unique behaviour of BEBs relative to beaches on the open coast, and that shifting wave direction needs to be considered in long‐term beach resilience under climate change. © 2020 John Wiley & Sons, Ltd.

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“…It must be noted that the dimensions of the rhythmic features in the study area differ from the published observations for small-scale finger bars, which are characterized by wavelengths spanning from 15 to 80 m and cross-shore spans ranging from 40 to 250 m [53][54][55]. In this case, the investigated features presented cross-shore spans from 3 to 18 times larger than the spacing observed between crests (depending on the area), aspect ratio not contemplated in the previous classification [52], being closer to the spacing observed for beach or lake cusps [9,56].…”

Section: Discussionmentioning

confidence: 97%

UAS Identify and Monitor Unusual Small-Scale Rhythmic Features in the Bay of Cádiz (Spain)

Talavera¹,

Benavente²,

Río³

2021

Remote Sensing

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Unusual shore-normal and barred-like rhythmic features were found in Camposoto Beach (Bay of Cádiz, SW Spain) during a monitoring program using unmanned aerial systems (UAS). They appeared in the backshore and persisted for 6 months (October 2017–March 2018). Their characteristics and possible formation mechanism were investigated analyzing: (1) UAS-derived high-resolution digital elevation models (DEMs), (2) hydrodynamic conditions, and (3) sediment samples. The results revealed that the features did not migrate spatially, that their wavelength was well predicted by the edge wave theory, and that they shared characteristics with both small-scale low-energy finger bars (e.g., geometry/appearance and amplitude) and swash cusps (e.g., wavelength, seaward circulation pattern, and finer and better sorted material in the runnels with respect to the crests). Our findings pinpoint to highly organized swash able to reach the backshore during spring tides under low-energy and accretionary conditions as well as backwash enhanced by conditions of water-saturated sediment. This study demonstrates that rhythmic features can appear under different modalities and beach locations than the ones observed up to date, and that their unusual nature may be attributed to the low spatiotemporal resolution of the traditional coastal surveying methods in comparison with novel technologies such as UAS.

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Morphology of a Low-Energy Beach, Como Beach, Western Australia

Cited by 37 publications

References 21 publications

Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration

Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

UAS Identify and Monitor Unusual Small-Scale Rhythmic Features in the Bay of Cádiz (Spain)

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