Abstract
Pocket beaches bound by headlands or other geologic features are common worldwide and experience constrained alongshore transport that influence their morphological changes. Pocket beaches fringed by shallow reefs have not been well-studied, yet can be commonly found throughout temperate and tropical regions. The presence of these reefs are expected to drive distinct hydrodynamics and shoreline responses to offshore waves and water levels, which is investigated in this study. To examine the parameters governing the shoreline variability, a 20-month field study was conducted on a reef-fringed pocket beach in southwestern Australia (Gnarabup Beach), using a series of in situ wave and water level observations, topographic surveys, as well as video shoreline monitoring. The results indicate the beach as a whole (alongshore averaged) was in a stable state. However, we observed substantial spatial variability of the local shorelines in response to offshore wave and water levels across a range of time-scales (from individual storms to the seasonal cycle). We observed local regions of beach rotations within cells partitioned by headlands and offshore reefs. The shoreline response was also dictated by the combination of offshore waves and water level which varied seasonally, with the shoreline generally retreating with lower water levels for the same wave height. Despite the contrasting responses in different alongshore locations of the beach, the overall beach volume of the pocket beach was largely conserved.
Highlights
Pocket beaches, in which a stretch of sandy shoreline is bounded by headlands or other features that impede alongshore sediment transport, occur globally across a wide range of wave exposure regimes
By further relating the erosion and accretion patterns of Cell 3A and B to larger offshore wave heights (>3.5 m) and the corresponding subtidal water levels across study period, we found that accretion at both Cells 3A and B mostly occurred during high subtidal water levels; for example, on 1 October 2016
A series of field observations over 20 months were used to assess the behavior of an embayed pocket beach fringed by rocky reefs in southwestern Australia
Summary
In which a stretch of sandy shoreline is bounded by headlands or other features that impede alongshore sediment transport, occur globally across a wide range of wave exposure regimes. Due to how these beaches are bound by barriers to sediment transport, they are often considered to be largely closed systems. Pocket beaches can be dominated by both cross-shore transport processes, that are primarily controlled by the incident wave energy (Harley et al, 2011; Blossier et al, 2017a), or alongshore transport that may cause beach rotation (Dehouck et al, 2009; Daly et al, 2014). Pocket beaches are commonly fringed by coral or rocky reefs that create a semiprotected lagoon, which may have a significant influence on the beach morphodynamics processes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
