Mechanisms and timescales of beach rotation

Loureiro, Carlos; Ferreira, Óscar

doi:10.1016/b978-0-08-102927-5.00024-2

Cited by 8 publications

(13 citation statements)

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“…Hence, longshore transport was evident at Portrush sectors that are included within a morphological sediment cell [9] enclosed by a harbour, in the northern end, and a headland in the southern end. The northern sector presented erosion while the southern sector accreted, probably from a point of pivoting in beach planform located in between the two sectors as observed at other morphological cells [9,62], which is consistent with a short-term rotational response identified in small embayments in various other settings [63][64][65] and in other studies of large embayed beaches [66][67][68].…”

Section: Discussionsupporting

confidence: 87%

Spatial Variability of Beach Impact from Post-Tropical Cyclone Katia (2011) on Northern Ireland’s North Coast

Anfuso

Loureiro

Taaouati

et al. 2020

Water

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In northern Europe, beach erosion, coastal flooding and associated damages to engineering structures are linked to mid-latitude storms that form through cyclogenesis and post-tropical cyclones, when a tropical cyclone moves north from its tropical origin. The present work analyses the hydrodynamic forcing and morphological changes observed at three beaches in the north coast of Northern Ireland (Magilligan, Portrush West’s southern and northern sectors, and Whiterocks), prior to, during, and immediately after post-tropical cyclone Katia. Katia was the second major hurricane of the active 2011 Atlantic hurricane season and impacted the British Isles on the 12–13 September 2011. During the Katia event, offshore wave buoys recorded values in excess of 5 m at the peak of the storm on the 13 September, but nearshore significant wave height ranged from 1 to 3 m, reflecting relevant wave energy dissipation across an extensive and shallow continental shelf. This was especially so at Magilligan, where widespread refraction and attenuation led to reduced shore-normal energy fluxes and very minor morphological changes. Morphological changes were restricted to upper beach erosion and flattening of the foreshore. Longshore transport was evident at Portrush West, with the northern sector experiencing erosion while the southern sector accreted, inducing a short-term rotational response in this embayment. In Whiterocks, berm erosion contributed to a general beach flattening and this resulted in an overall accretion due to sediment influx from the updrift western areas. Taking into account that the post-tropical cyclone Katia produced £100 m ($157 million, 2011 USD) in damage in the United Kingdom alone, the results of the present study represent a contribution to the general database of post-tropical storm response on Northern European coastlines, informing coastal response prediction and damage mitigation.

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Section: Discussionsupporting

confidence: 87%

Spatial Variability of Beach Impact from Post-Tropical Cyclone Katia (2011) on Northern Ireland’s North Coast

Anfuso

Loureiro

Taaouati

et al. 2020

Water

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“…However, different embayment widths, headland lengths and wave climate may have a profound impact on the relative contributions of cross-shore and longshore processes to rotation signal. In addition, other morphodynamic processes (see review of Loureiro and Ferreira, 2020) can affect embayment rotation, such as for instance shoreline-sandbar-coupled rotation driven by strong longshore components during storms (van de Lageweg et al, 2013), or high-energy rips flowing against the headland (Loureiro et al, 2012b). More shoreline modelling is required on real embayed beaches with different hydrodynamic and geological settings, in order to better constrain academic modelling experiments and gain generic knowledge of the processes driving rotation.…”

Section: Discussionmentioning

confidence: 99%

“…Clockwise/counterclockwise rotation of the embayed beach planform has been commonly observed as the dominant pattern of shoreline variability at embayed beaches (Masselink and Pattiaratchi, 2001;Short and Trembanis, 2004;Ranasinghe et al, 2004;Martins and de Mahiques, 2006;Thomas et al, 2011;Loureiro et al, 2012a;Turki et al, 2013a;Van de Lageweg et al, 2013;Harley et al, 2013;Robinet et al, 2020a). Loureiro and Ferreira (2020) reviewed the mechanisms and timescales of beach rotation at embayed beaches. Beach rotation has long been attributed to longshore transport processes, when enough sediment moves from one side of the embayment to the other to shift the mean orientation of the beach (Ratliff and Murray, 2014).…”

Section: Introductionmentioning

confidence: 99%

Modelling of embayed beach equilibrium planform and rotation signal

Castelle

Robinet²,

Idier

et al. 2020

Geomorphology

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Embayed beaches are highly attractive sandy beaches bounded laterally by rigid boundaries, which deeply affect equilibrium beach planform and shoreline dynamics. We use LX-Shore, a state-of-the-art shoreline change model coupled with a spectral wave model to address embayed beach shoreline dynamics driven by longshore sediment transport processes. The model is applied to different Highlights • Embayed beach shoreline response is simulated with a hybrid shoreline model • Headland length and headland sediment bypassing control shoreline response • Wave directional spreading is critical to both mean shoreline and rotation signal • Embayment beach length controls rotation characteristic timescale

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“…Due to the inherent alongshore compartmentalisation and exposure to temporal and spatially variable wave conditions, beach rotation is a common phenomenon on geologically controlled beaches (Gallop et al, 2013;Habel et al, 2016;Trenhaile, 2016). Beach rotation can be defined as the alternating morphological response of opposite sections of an embayed beach, driven by cross-shore and/or longshore morphodynamic processes or their interaction, coupling the beach and nearshore in response to changes in hydrodynamic forcing (Loureiro and Ferreira, 2020). Beach rotation occurs mainly through alongshore and/or cross-shore nonuniform sediment transport due to variation in wave direction and/or gradients in wave energy (Harley et al, 2011;Harley et al, 2015), but can also be driven by cellular circulation mechanisms (Loureiro et al, 2012b).…”

Section: Beach Rotationmentioning

confidence: 99%

Geologically controlled sandy beaches: Their geomorphology, morphodynamics and classification

Gallop

Kennedy

Loureiro

et al. 2020

Science of The Total Environment

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Beaches that are geologically controlled by rock and coral formations are the rule, not the exception. This paper reviews current understanding of geologically controlled beaches, bringing together a range of terminologies (including embayed beaches, shore platform beaches, relict beaches, and perched beaches among others) and processes, with the aim of exploring the multiple ways in which geology influences beach morphology and morphodynamics. We show how in addition to sediment supply, the basement geology influences where beaches will form by providing accommodation, and in the cross-shore, aspects of rock platform morphology such as elevation and slope are also important. Geologically controlled beaches can have significant variations in sediment coverage with seasons and storms, and geological controls have fundamental influences on their contemporary morphodynamics. This includes wave shadowing by headlands and rocky/coral formations inducing strong alongshore gradients in wave energy, resulting in corresponding variations in morphodynamic beach state and storm response. Geologically-induced rip currents such as shadow rips and deflection rips, and even mega-rips that can develop on embayed beaches during storms, are an integral feature of the nearshore circulation and morphodynamics of geologically controlled beaches. We bring these processes together by presenting a conceptual model of alongshore and cross-shore levels of geological control. In the longshore dimension, this ranges from beaches that are slightly embayed, through to highly embayed beaches where headlands dominate the entire beach morphodynamic response. In the cross-shore dimension, this ranges from beaches without discernible geological controls, through to relict beaches above the influence of the contemporary littoral zone. Given the prevalence of geologically controlled beaches along the world's coasts, it is paramount for coastal management to consider how these beaches differ from unconstrained beaches and avoid applying inappropriate models and tools, especially with our uncertain future climate.

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Mechanisms and timescales of beach rotation

Cited by 8 publications

References 58 publications

Spatial Variability of Beach Impact from Post-Tropical Cyclone Katia (2011) on Northern Ireland’s North Coast

Spatial Variability of Beach Impact from Post-Tropical Cyclone Katia (2011) on Northern Ireland’s North Coast

Modelling of embayed beach equilibrium planform and rotation signal

Geologically controlled sandy beaches: Their geomorphology, morphodynamics and classification

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