Seasonal morphodynamics of multiple intertidal bars (MITBs) on a meso? to macrotidal beach

Multiple intertidal bar (MITB) beach systems comprise a succession of subdued, shore-parallel sandbars, developed under low-energy conditions in meso- to macrotidal settings. Their relatively stable morphologies over long timescales are commonly attributed dynamic equilibrium, driven primarily by seasonal morphodynamics. The behaviour is, however, poorly understood. relationship between temporal and spatial hydrodynamic forcing morphological changes was investigated through monthly differential GPS surveys Dundrum Bay (Northern Ireland) from April 2019 March 2020, associated with variations nearshore wave conditions, simulated using the SWAN model. During summer southeast waves helped promote MITB stability slight increase crest elevation, seaward-most buffering preserving inner system dissipation. In winter, progressive energy, switch direction (southwest south), initiated highest rates cross-shore migration lowering crests. While remained largely submerged, shoreward-most played key role protecting upper-beach and/or foredune. Winter also forced newly observed mesoscale longshore drift involving offshore sediment transport southwest onshore northeast. Cross-shore variability at was, local including energy direction. Conversely, alongshore influenced complex bathymetry, headlands an active ebb delta, all interacting changing forcing. These results challenge equilibrium model for highlight longer-term patterns movement.