Monitoring the nearshore currents pattern along the anthropogenically influenced coast of Puducherry

Understanding the characteristics of nearshore hydrodynamics has always been difficult due to the practical necessity of deploying an array of sensors to demonstrate the spatial variability of coastal processes. Lagrangian data collection techniques are frequently used to gather valuable information on the complex flow structure along the coast, both spatially and temporally. The present study uses multiple field-measured datasets to investigate the dynamics of nearshore currents along a wave-dominated coastal stretch of Puducherry, located on India's East Coast. The observations were also used to validate the hydrodynamic model. In-situ data collected with Lagrangian GPS drifters during three seasons in 2017 show that wave action and strong seaward winds significantly influence nearshore surface currents. Furthermore, the observation revealed that nearshore currents change direction from north to south due to seasonal variation and are influenced by coastal anthropogenic features. The hydrodynamics computed from a three-dimensional numerical model created with Delft3D agree well with in-situ measurements. After the calibration process, the values of 0.025 and 14 m 2 /s were found to be the optimal values of bottom friction and eddy viscosity for Lagrangian-based comparison. However, the simulated drogue trajectories revealed some uncertainties due to model input parameters such as grid discretization, bathymetry, boundary condition, and input of ocean circulation outside the surf zone.