Impact of seasonal wave hydrodynamics on beach morphology and sediment grain size along the central west coast of India

Abstract

Knowledge of seasonal sediment dynamics along monsoon-dominated coasts is paramount in evaluating beach resilience and coastal management. This study investigates textural and volumetric variations in three open-coast beaches of South Goa (Utorda, Benaulim, and Cavelossim) during pre-monsoon, monsoon, and post-monsoon seasons in 2021–2022, including the effect of Cyclone Tauktae. Monthly beach profiles and sediment samples were analysed to measure grain size parameters (Mean, Skewness, Kurtosis and Sorting), and volumetric variations. Results indicate a repetitive pre-monsoon accretion and textural fining seasonal cycle, preceded by massive monsoonal erosion (in excess of 70% volume loss at certain locations) and coarsening, followed by post-monsoon recovery with volumetric restoration but worse sorting. Site-specific trends emphasize local geomorphic control, Utorda recorded repetitive and stable textural reorganization, Benaulim recorded robust volumetric recovery but chronic post-monsoon instability, whereas Cavelossim reflected anomalous monsoon sorting attributed to longshore transport. Cyclone Tauktae induced sudden erosion (>60% volume reduction) and coarsening over a span of one month, similar in nature to monsoonal effects but compressed in timescale. Statistical tests returning limited significance (probability value(p) > 0.05) are even though that consistent trends over years highlight the strength of monsoon-controlled processes. These results indicate that the Monsoon is the predominant controller of beach morphodynamics but local geomorphology and occasional cyclones filter the extent and character of response. Implications of this research offer a basis for site-specific monitoring and adaptive management under envisioned climate-driven enhancement of monsoon variability and extreme events.