Modeling the Morphodynamic Response of Estuarine Intertidal Shoals to Sea-Level Rise

H. Elmilady*, M. van der Wegen, D. Roelvink, A. van der Spek

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)
63 Downloads (Pure)

Abstract

Intertidal shoals are key features of estuarine environments worldwide. Climate change poses questions regarding the sustainability of intertidal areas under sea-level rise (SLR). Our work investigates the SLR impact on the long-term morphological evolution of unvegetated intertidal sandy shoals in a constrained channel-shoal system. Utilizing a process-based model (Delft3D), we schematize a short tidal system in a rectangular (2.5 × 20 km) basin with a high-resolution grid. An initial, mildly sloping, bathymetry is subjected to constant semidiurnal tidal forcing, sediment supply, and small wind-generated waves modeled by SWAN. A positive morphodynamic feedback between hydrodynamics, sediment transport, and morphology causes the emergence of large-scale channel-shoal patterns. Over centuries, tide-residual sediment transport gradually decreases leading to a state of low morphological activity balanced by tides, waves, and sediment supply. Tidal currents are the main driver of the SLR morphodynamic adaptation. Wave action leads to wider and lower shoals but does not fundamentally change the long-term morphological evolution. SLR causes increased flood dominance which triggers sediment import into the system. Shoals accrete in response to SLR with a lag that increases as SLR accelerates, eventually causing intertidal shoals to drown. Seaward shoals near the open boundary sediment source have higher accretion rates compared to landward shoals. Similarly, on a shoal-scale, the highest accretion rates occur at the shoal edges bounding the sediment suppling channels. A larger sediment supply enhances the SLR adaptation. Waves help distribute sediment supplied from channels across shoals. Adding mud fractions leads to faster, more uniform, accretion and muddier shoals under SLR.

Original languageEnglish
Article numbere2021JF006152
Number of pages26
JournalJournal of Geophysical Research: Earth Surface
Volume127
Issue number1
DOIs
Publication statusPublished - 2022

Keywords

  • Delft3D
  • Intertidal shoals
  • Long-term morphological evolution
  • Process-based modeling
  • Sea-level rise
  • Waves

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