Abstract
Abstract. Researchers have extensively investigated the back-barrier islands morphodynamics using numerical methods. However, the influence of rocky mouth islands, which may be submerged by sea-level rise, has been rarely explored. Using the Dongshan Bay in southern China as a reference, this study numerically explores the long-term morphodynamic effect of geological constraints (e.g. rocky islands) for back-barrier basins. Model results indicate that the spatial configuration of mouth islands can considerably affect the morphological development of tidal basins. The presence of mouth islands narrows the inlet cross-sectional area, increasing flow velocity and residual current, resulting in more sediment suspension and transport. Meanwhile, mouth islands tend to increase erosion in the tidal basin and sedimentation in the ebb-delta area. Furthermore, the spatial distribution of mouth islands can also affect tidal basin evolution: the basin-side mouth islands tend to cause more basin erosion with higher tidal currents and more sediment transport. In contrast, the delta-side ones may increase relative sediment deposition in the basin. Finally, larger tidal prisms are observed with more mouth islands and with basin-side mouth islands, suggesting that the number and location of islands can affect the relationship between the tidal prism and inlet cross-sectional area. This modelling study furthers the understanding of barrier basin morphodynamics affected by rocky mouth islands and informs management strategies under a changing environment.
Highlights
During the post-glacial sea-level rise, many low-lying basins and valleys were submerged, forming various embayed coasts and mouth islands, accounting for 10 %–15 % of the world’s coastline (de Swart and Zimmerman, 2009; FitzGerald and Miner, 2013)
Hydrodynamics can shape the geomorphic characteristics of coastal landforms through sediment transport, while the landforms can feedback to hydrodynamics, forming a morphodynamic loop that eventually drives the system to some sort of dynamic equilibrium state (Coco et al, 2013; Zhou et al, 2017)
Results indicate that the flow velocity and residual currents increase with the number of islands, enhancing the sediment transport and bed-level change near the inlet
Summary
During the post-glacial sea-level rise, many low-lying basins and valleys were submerged, forming various embayed coasts and mouth islands, accounting for 10 %–15 % of the world’s coastline (de Swart and Zimmerman, 2009; FitzGerald and Miner, 2013). Morphodynamics of back-barrier systems is affected by the interaction of various factors, including hydrodynamic processes (e.g. tides and waves), biological activities (e.g. presence of mangroves and salt marshes), climate change (e.g. global warming and sea-level rise) and anthropogenic. Y. Wei et al.: The role of geological mouth islands activities (e.g. land reclamation and artificial construction) (Murray et al, 2008). Wei et al.: The role of geological mouth islands activities (e.g. land reclamation and artificial construction) (Murray et al, 2008) These processes result in an everchanging morphology of tidal channels, tidal flats and flood/ebb deltas (Wang et al, 2012). Hydrodynamics can shape the geomorphic characteristics of coastal landforms through sediment transport, while the landforms can feedback to hydrodynamics, forming a morphodynamic loop that eventually drives the system to some sort of dynamic equilibrium state (Coco et al, 2013; Zhou et al, 2017)
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