Hypothesis-driven sensitivity analysis of Delft3D flexible mesh hydrodynamic model: insights into coastal processes in the monsoonal tropical Goa Coast, India
Date
2025Author
Okon, L.-U. E.,
Jayakumar, S.
Hemanath, L.,
Thomas, J.
& Narine, R.
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Accurate numerical modeling of coastal hydrodynamics in tropical monsoonal environments remains challenging because of parameter uncertainties and nonlinear process interactions. This study presents a hypothesis-driven, comprehensive sensitivity analysis of the Delft3D Flexible Mesh (DFM) hydrodynamic model applied to the Goa coast, a tropical monsoonal coastal system along the Central West Coast of India. Using multi-seasonal field observations and rigorous model calibration and validation, we systematically investigate the influence of three key input parameters: Manning�s bottom roughness coefficient, horizontal eddy viscosity, and the JONSWAP bottom friction coefficient, on the accuracy of model outputs of tidal current velocities, water levels, and significant wave height. The model showed excellent performance in predicting tidal currents, with correlation coefficients (R2) exceeding 0.87 for most observation sites. The model�s ability to simulate wave height was validated with R2 values of 0.76 for significant wave height at the North Goa station. Results confirm that Manning�s coefficient strongly governs current velocity predictions, consistent with classical hydrodynamic boundary layer theory, while eddy viscosity and diffusivity have a secondary but essential role in resolving shear and mixing processes. The JONSWAP bottom friction coefficient significantly affects wave height attenuation modulation, aligning with seabed-wave interaction dynamics. Notably, an inverse relationship between Manning�s coefficient and velocity arises in the Zuari River, highlighting limitations of two-dimensional modeling in complex estuarine flows, pointing to the need for enhanced three-dimensional modeling approaches. By integrating multi-seasonal field data with theory-based analysis, this work advances understanding of tropical coastal hydrodynamics and informs improved model calibration strategies essential for sustainable coastal management under monsoonal variability.
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