Sediment characteristics, distribution and pathways on a macro-tidal, energetic and sediment-limited embayed coast

In addition to external hydrodynamic forcing, the behaviour of beach–dune systems is strongly controlled by nearshore sediment availability and coastal transport pathways. Here we integrate new sedimentological observations, shoreface geomorphological analysis, and regional hydrodynamic modelling to improve understanding of the distribution, characteristics, and connectivity of mobile sediments along a macro-tidal, high-energy, sediment-limited embayed coastline in Cornwall, United Kingdom. We first map the spatial extent of mobile sand bodies along a 45-km coastline and assess headland bypassing potential to define coastal embayments. Coast-wide sediment samples ( n = 348), spanning dunes to the lower shoreface, were classified using K-means clustering of grain-size and mineralogical data to quantify spatial variability in sediment character, refine the identification of closed/constrained embayments, and evaluate existing regional sediment transport modelling. Eight closed coastal cells and four major sediment sinks, associated with large dune systems, were identified, together with a dominant southwest-to-northeast transport pathway. Sediment-starved regions exhibited the highest calcium carbonate contents (45–57%), consistent with long-term sediment supply limitations. These results demonstrate the value of spatially comprehensive sediment resource and geomorphological datasets for constraining sediment pathway modelling and provide a scientific basis for evaluating long-term coastal evolution.