Morphological evolution of a complex drift‐aligned prograded barrier

• Published in: Earth surface processes and landforms Vol. 49; no. 2; pp. 728 - 745
• Main Authors: Carvalho, Rafael Cabral, Mueller, Daniela, Reef, Ruth
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.02.2024
• Subjects: Accretion; asymmetrical ridges; barrier evolution; Coastal landforms; Coastal management; Coastal zone management; Holocene; Landforms; Lidar; longshore drift; Morphology; OSL; Ridges; Sand; Sediment; Sediment movement; Sediments; Shorelines; Storms; strandplain; Tidal circulation; truncated ridges
• ISSN: 0197-9337; 1096-9837
• DOI: 10.1002/esp.5732

Prograded barriers are coastal landforms with a worldwide distribution that provide a paleoenvironmental record within a sequence of successive ridges and intervening swales. Most barriers with variable terrestrial morphologies, also known as complex barriers, have been poorly studied. At the main entrance of Western Port, a bay in southeastern Australia, a morphologically complex barrier was formed as a function of its somewhat sheltered position and orientation in relation to sporadic swells and tidal circulation. LiDAR‐derived topography shows highly truncated and asymmetrical ridges both across and along the Somers–Sandy Point barrier plain. These uncommon morphologies are associated with an intricate hydrodynamic circulation subject to sporadic storms approaching at a sharp angle to the shoreline that eliminate a significant part of the sedimentary record but also redistribute vast quantities of sand to the downdrift shoreline, and a large and variable sandy bank that undergoes intense sediment movement. Optically stimulated luminescence (OSL) dating within a limited area on the western side revealed an age of ~2600 years for the innermost dated ridge, located about halfway across the plain. Significant erosion of the ridges' record occurred on the western side of the barrier between 2600 and 700 years ago and between 600 and 240 years ago, whereas undated ridges on the eastern side were preserved. This creates an opportunity for future research on past erosional events that would be of great value for coastal management and adaptation. Textural and elemental (XRF) sediment characteristics suggest that the type of material provided for barrier accretion remained the same throughout the late Holocene. Given the sustained growth of the barrier and other sandy parts of the bay, a net supply of marine sand from Bass Strait must have occurred. The proposed evolutionary model contributes to the understanding of the sediment budget for the bay as a whole. We studied a morphologically complex strandplain exhibiting unusual highly truncated and asymmetrical ridges formed at the entrance of a bay due to its sheltered position, orientation and hydrodynamics. OSL dating and LiDAR revealed that half of the barrier was formed in the past 2600 years and that significant parts of the plains were eliminated by many phases of erosion. Remnant sedimentary record can shed light on Holocene erosional events and be of great value for coastal management and adaptation.