| Abstrakt: |
Several field and model studies indicate that the decadal evolution of shorelines is affected by the presence of shoreface‐connected sand ridges (sfcr) and tidal sand ridges (tsr) on the shelf. This study uses a coupled shelf‐nearshore numerical model to quantify the joint impact of tsr and sfcr on decadal shoreline evolution. Additionally, it examines the dependence of this evolution on cross‐shore and longshore displacements of the sfcr, thereby mimicking the observed cross‐shore and longshore migrations of sfcr on the shelf. Model results indicate shoreline progradation near the crests of the sfcr and retreat near the channels between the ridges and the coast, consistent with observations. Compared to sfcr, the impact of tsr on nearshore dynamics is smaller yet significant. When the sfcr are positioned closer to the shore, shoreline progradation and retreat become stronger. These shoreline undulations have amplitudes that strongly increase as sfcr approach the shoreline, and the undulations shift alongshore with the alongshore shift of the sfcr. Based on these results, it is anticipated that the observed onshore and alongshore migration of sfcr on the shelf will enhance shoreline retreat near the channels and progradation near sfcr crests, with these shoreline changes migrating alongshore with the ridges. Plain Language Summary: This study investigates how sand ridges on the shelf, specifically shoreface‐connected sand ridges (sfcr) and tidal sand ridges (tsr), shape shorelines over decades. By using a coupled shelf‐shoreline model that simulates both the shelf and nearshore areas, this study quantifies how the sfcr and tsr together affect the shoreline shape. It also investigates how the shoreline shape changes when the sfcr move toward or along the shore, replicating natural movements of sfcr seen on the shelf. Model results show that shorelines expand seaward near the tops of sfcr and retreat landward near the channels between these ridges and the shore, which matches what has been observed in nature. Although tsr also influence the shoreline shape, their impact is smaller compared to sfcr. If the sfcr are closer to the shore, the changes in shoreline shape‐both expansion and retreat‐are more pronounced. These changes also shift alongshore with the alongshore shift of sfcr. This study indicates that onshore and alongshore movements of sfcr observed on the shelf are expected to enhance shoreline expansion near the tops of sfcr and retreat near the channels, with these changes following the movements of the ridges. Key Points: Results of a coupled shelf‐nearshore model quantify how shoreface‐connected ridges (sfcr) and tidal ridges (tsr) affect shoreline evolutionModel results show shoreline progradation near sfcr crests, retreat near channels, with the impact of tsr being smaller but non‐negligibleShoreline undulations grow stronger when sfcr are closer to the shore and their alongshore shift is slaved to that of the sfcr [ABSTRACT FROM AUTHOR] |
Plný text