Origins of Holocene coastal strandplains in Southeast Australia: Shoreface sand supply driven by disequilibrium morphology

Kinsela, Michael A.; Daley, Marc; Cowell, Peter J.

doi:10.1016/j.margeo.2016.01.010

Cited by 62 publications

(48 citation statements)

References 57 publications

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“…Kinsela et al . () have demonstrated the role of an inherited disequilibrium shoreface profile as a key driver of onshore accumulation of sandy sediments forming prograded barriers on the central NSW coast. At Pedro, the progressive down‐wearing of the shoreface as sediment is moved onshore to form the barrier, may have exposed much of the rocky reef now evident to the northeast and southeast of the current shoreline position (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Rapid shoreline progradation followed by vertical foredune building at Pedro Beach, southeastern Australia

Oliver

Tamura

Short

et al. 2018

Earth Surf Processes Landf

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At Pedro Beach on the southeastern coast of Australia a series of foredune ridges provides an opportunity to explore the morphodynamic paradigm as it applies to coastal barrier systems using optically stimulated luminescence (OSL) dating, ground penetrating radar (GPR) and airborne LiDAR topography. A series of sandy dune‐capped ridges, increasing in height seawards, formed from c. 7000 years ago to c. 3900 years ago. During this time the shoreline straightened as the embayment filled and accommodation space for Holocene sediments diminished. Calculation of Holocene sediment accumulation above mean sea level utilising airborne LiDAR topography shows a decline in average sediment supply over this time period coupled with a decrease in shoreline progradation rate from 1.2 m/yr to 0.38 m/yr. The average ridge ‘exposure lifetime’ during this period increases resulting in higher ridges as dune‐forming processes have longer to operate. Increasing exposure to wave and wind energy also appears to have resulted in higher ridges as the sheltering effect of marginal headlands was diminished. An inherited disequilibrium shoreface profile will drive onshore accumulation of sandy sediments forming a prograded barrier; however, if there is no longer ‘accommodation space’ for sediment, this will be an overriding factor causing the cessation of progradation, as occurred c. 3900 years ago at Pedro Beach. Excess sediment in the nearshore zone after 3900 years ago may have been moved northward to nourish downdrift beaches in the compartment. A high outer foredune has formed through vertical accretion after 500 years ago, evidenced by GPR subsurface structures and OSL ages, with a distinct period of vertical and lee slope accretion and dated to the period 1890–1930 AD. The increased dune sediment transport resulting in foredune building is attributed to recent human disturbance. © 2018 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Rapid shoreline progradation followed by vertical foredune building at Pedro Beach, southeastern Australia

Oliver

Tamura

Short

et al. 2018

Earth Surf Processes Landf

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“…The occurrence of prograded Holocene sand barriers along parts of the central and southern NSW coast, where fluvial sources and the alongshore sand transport system is limited, suggests that shoreface sand supply to beaches was an important process during recent geological time, and may persist today at significant rates along some parts of the coast [24,90,91]. That potential was considered using the regional rates of sand supply to NSW beaches" which was derived from the analysis of geohistorical records spanning the last several centuries [87], which was applied as annual average rates of sand supply using the q x parameter (Equation (3)).…”

Section: Model Applicationsmentioning

confidence: 99%

“…In reality, whether the shoreface represents a source or sink at each NSW beach will depend on the relationship between present shoreface geomorphology and the prevailing depositional controls (e.g., sediment distribution, type, and availability, and the energy regime). The presence of Holocene prograded barriers along parts of the central and southern NSW coasts is evidence that some of the shorefaces have acted as a source of sediments for adjacent beaches during the mid to late Holocene [24,90,91]. Whether or not the shoreface remains a significant source of sand supply for these NSW beaches, particularly under conditions of accelerating sea-level rise, remains an area of ongoing research [91].…”

Section: Modelling Approach and Limitationsmentioning

confidence: 99%

“…The presence of Holocene prograded barriers along parts of the central and southern NSW coasts is evidence that some of the shorefaces have acted as a source of sediments for adjacent beaches during the mid to late Holocene [24,90,91]. Whether or not the shoreface remains a significant source of sand supply for these NSW beaches, particularly under conditions of accelerating sea-level rise, remains an area of ongoing research [91]. Along the lower gradient northern NSW coast and shelf (Figure 1), the complete filling of many embayments with Pleistocene barrier deposits (and consequent absence of Holocene barrier deposits) [43], and the strong northward alongshore transport system, together make it more difficult to determine the current depositional relationship between beaches and the shoreface.…”

Section: Modelling Approach and Limitationsmentioning

confidence: 99%

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Second-Pass Assessment of Potential Exposure to Shoreline Change in New South Wales, Australia, Using a Sediment Compartments Framework

Kinsela

Morris

Linklater

et al. 2017

JMSE

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Abstract:The impacts of coastal erosion are expected to increase through the present century, and beyond, as accelerating global mean sea-level rise begins to enhance or dominate local shoreline dynamics. In many cases, beach (and shoreline) response to sea-level rise will not be limited to passive inundation, but may be amplified or moderated by sediment redistribution between the beach and the broader coastal sedimentary system. We describe a simple and scalable approach for estimating the potential for beach erosion and shoreline change on wave-dominated sandy beaches, using a coastal sediment compartments framework to parameterise the geomorphology and connectivity of sediment-sharing coastal systems. We apply the approach at regional and local scales in order to demonstrate the sensitivity of forecasts to the available data. The regional-scale application estimates potential present and future asset exposure to coastal erosion in New South Wales, Australia. The assessment suggests that shoreline recession due to sea-level rise could drive a steep increase in the number and distribution of asset exposure in the present century. The local-scale example demonstrates the potential sensitivity of erosion impacts to the distinctive coastal geomorphology of individual compartments. Our findings highlight that the benefits of applying a coastal sediment compartments framework increase with the coverage and detail of geomorphic data that is available to parameterise sediment-sharing systems and sediment budget principles. Such data is crucial to reducing uncertainty in forecasts by understanding the potential response of key sediment sources and sinks (e.g., the shoreface, estuaries) to sea-level rise in different settings.

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“…Moreover, a decrease in cross‐shore sediment supply may also have contributed to the change in depositional regime. Several studies have shown that progressive reworking and extinguishing of a localized sediment source is important for sustaining coastal progradation (Timmons et al ., ; Kinsela et al ., ; Oliver et al ., ). Submerged barrier systems, located west of Rømø (Fruergaard et al ., ,b), may have constituted such sediment sources that became depleted about 4000 to 5000 years ago resulting in a decreasing sediment supply to Rømø.…”

Section: Discussionmentioning

confidence: 99%

Sedimentary architecture and depositional controls of a Holocene wave‐dominated barrier‐island system

et al. 2017

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Barrier‐island system evolution is controlled by internal and external forcing mechanisms, and temporal changes in these mechanisms may be recorded in the sedimentary architecture. However, the precise role of individual forcing mechanisms is rarely well understood due to limited chronological control. This study investigates the relative role of forcing conditions, such as antecedent topography, sea‐level rise, sediment supply, storms and climate changes, on the evolution of a Holocene wave‐dominated barrier‐island system. This article presents temporal reconstruction of the depositional history of the barrier‐island system of Rømø in the Wadden Sea in unprecedented detail, based on ground‐penetrating radar profiles, sediment cores, high‐resolution dating and palynological investigations, and shows that ca 8000 years ago the barrier island formed on a Pleistocene topographic high. During the initial phase of barrier evolution, the long‐term sea‐level rise was relatively rapid (ca 9 mm year−1) and the barrier was narrow and frequently overwashed. Sediment supply kept pace with sea‐level rise, and the barrier‐island system mainly aggraded through the deposition of a ca 7 m thick stack of overwash fans. Aggradation continued for ca 1700 years until sea‐level rise had decreased to <2 mm year−1. In the last ca 6000 years, the barrier prograded 4 to 5 km through deposition of a 10 to 15 m thick beach and shoreface unit, despite a long‐term sea‐level rise of 1 to 2 mm year−1. The long‐term progradation was, however, interrupted by a transgression between 4000 years and 1700 years ago. These results demonstrate that the large‐scale morphology of the Danish Wadden Sea shoreline influences the longshore sediment transport flux and the millennial‐scale dispersal of sediment along the shoreline. On decadal to centennial timescales, major storms induced intense beach and shoreface erosion followed by rapid recovery and progradation which resulted in a highly punctuated beach and shoreface record. Major storms contributed towards a positive sediment budget, and the sustained surplus of sediment was, and still is, instrumental in maintaining the aggradational–progradational state of the barrier island.

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Origins of Holocene coastal strandplains in Southeast Australia: Shoreface sand supply driven by disequilibrium morphology

Cited by 62 publications

References 57 publications

Rapid shoreline progradation followed by vertical foredune building at Pedro Beach, southeastern Australia

Rapid shoreline progradation followed by vertical foredune building at Pedro Beach, southeastern Australia

Second-Pass Assessment of Potential Exposure to Shoreline Change in New South Wales, Australia, Using a Sediment Compartments Framework

Sedimentary architecture and depositional controls of a Holocene wave‐dominated barrier‐island system

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