Monsoon-induced seasonal variability of sheltered versus exposed beaches along the West coast of India

Abstract

Changes in profile configuration of the beaches at different locations along the west coast of India have been quantitatively compared by means of Empirical Orthogonal Function (EOF) analysis. These beaches, though exposed to similar monsoonal forcings, respond through variable changes depending on their individual geographical/geomorphological setting. The analysis suggests that, for the period of study, the beaches are stable as revealed by the temporal dependence of the first eigenfunction. The second function reveals the significant erosional/accretional phases with a well defined cyclicity of one year associated with monsoonal wind and wave climate. The second spatial function efficiently expresses a "pivot point" for the seasonal shore-normal movement of sand. The depth at which this pivot point occurs is inversely related to the width of the beach. The differential energy environments, even over short distances, are found to be the prime factors that determine the magnitude of temporal beach variability. Unprotected beaches showed higher magnitudes of variability. These results suggest that the second eigenfunction and the variance of the data set are more useful than the other order eigenfunctions for a comparative study of this kind.