Dynamics of Longshore Sediment Transport under Different Energy Conditions along the Andhra Pradesh Coast

The dynamics of longshore sediment transport (LST) significantly influence the shape of sandy coastlines, especially in monsoon-affected areas like the Andhra Pradesh coast. In this study, we calculated the Longshore Sediment Transport Rate (LSTR) for both the medium-energy coast of the southern sector and the low-energy coast of the central sector of Andhra Pradesh, located on the east coast of India, using a numerical model. We used multi-year wave climate data from pre-monsoon, monsoon, and post-monsoon seasons to measure transport rates for low, moderate, and high-energy wave conditions. The results shows considerable changes over time and space, with sediment movement peaking during monsoon months due to higher wave heights and angled impacts. In contrast, transport was much lower during fair-weather periods. A comparison of the CERC and Kamphuis equations revealed that each method responds differently, with the Kamphuis equation offering a better fit during storms. An assessment of different districts also showed variations in transport levels based on local shoreline direction and nearshore depths. District-wise analysis showed notable differences in transport volumes. For example, Krishna and Nellore districts experienced peak transport rates of over 2.5 m³/s during the post-monsoon and monsoon seasons. In contrast, areas like Konaseema and West Godavari, which are sheltered or have structural limitations, had much lower transport volumes of less than 0.3 m³/s. Coastal features such as headlands, river mouths, and seawalls significantly affect sediment convergence and divergence zones. These results highlight the strong influence of seasonal wave patterns on sediment movement and provide essential information for coastal management, particularly in areas facing beach erosion, harbor silting, and infrastructure risks.