Sediment dynamics of tropical open coast beaches, central west coast of India: implications of spatio-temporal variability

Local and regional climatic pressures influence coastal geomorphic systems on different spatial and temporal scales. Within these zones of variation, systems and environmental processes interact. They can recreate sediment movement patterns and anticipate environmental evolution. This study utilises a non-parametric end-member modelling analysis (EMMA) as a deterministic approach for unmixing grain sizes into geologically relevant populations. The aim is to characterise seasonal grain size distribution variation and link seasonal end members to proximal sources. A 5-year analysis of seasonal data from 19 open-coast beaches is adopted in the North and South Goa coastal area. End-members (EMs) are assigned based on grain size modal classes of 32–63 µm (EM1), 63–125 µm (EM2), 125–250 µm (EM3), and 250–500 µm (EM4), corresponding to coarse silt, very fine sand, fine sand, and medium sand respectively. In response to the current hydrodynamic forcings, it is projected that the surface sediments analysed have been reworked, sorted, and redistributed. While the spatial trend of EM distribution indicates an abundance of EM2 and EM3 along the coast, the variability in EMs across seasons shows that the Southwest and Northeast monsoons significantly influence the distributions of sediments along the Goa Coast, and the underlying EMs in the sediments bear the imprint of the interaction of these two seasons' dominant forces.