Beach dynamics of an open coast on the west coast of India

Abstract

In order to study the daily beach dynamics at an open beach in Goa, field investigations were carried out on the beach profiles, breaking wave parameters and long-shore currents for one month each during pre-monsoon and post-monsoon periods. Three transects on the Calangute Beach, Goa, India, spaced about 250 m apart were selected. Pre-monsoon breaking wave heights were observed to be between 0.4 and 1.3 m and the wave period between 5 and 11 s, whereas, the post-monsoon breaking wave heights were between 0.35 and 1.4 m with the periods ranging between 8 and 15 s. Pre-monsoon long-shore currents were stronger (max. 1 m/s) and varying in direction compared to post-monsoon (max. 0.66m/s) wherein the direction was predominantly north. Post-monsoon foreshore slopes were found to be mild and the berms wider compared to the pre-monsoon beaches. Inter-tidal beach sediments in the pre-monsoon period were coarse compared to post-monsoon sediments. Average estimated long-shore sediment transport rate in the study region indicates that the gross long-shore sediment transport was high during pre-monsoon compared to the post-monsoon. The net transport was southwards and about 0.013x10 sup(6) m sup(3)/year during the pre-monsoon and it was northerly and about 0.007x10 sup(6) m sup(3)/year during the post-monsoon. Whereas, the average gross transport rate was 0.02x106 m sup(3)/year during the pre-monsoon it was 0.014x10 sup(6) m sup(3)/year during the post-monsoon.