ABSTRACT

Dabu, R. and Cruz, E., 0000. Hybrid 2D-1D shoreline morphology modeling for a low-energy semi-enclosed tropical coast.

A hybrid coastal morphology model was applied to simulate shoreline evolution and sediment transport along Sariaya, Quezon Province, Philippines. The model couples a two-dimensional (2DH) hydrodynamic and spectral wave model with a one-dimensional (1D) shoreline evolution module (MIKE21 Shoreline Morphology). The study area is a low-wave-energy tropical coast characterized by monsoonal wind patterns and a tidal range of about 1.5 m. Model setup involved high-resolution nested three-layer meshes (domains: Philippine archipelago, Tayabas Bay, nearshore of Sariaya), with forcing from global tide predictions and Climate Forecast System Reanalysis wind data. The hydrodynamic module was calibrated against two months of observed water levels during the NE monsoon (Amihan) season, showing excellent agreement (water-level predictions were largely insensitive to bed friction parameters, Manning’s n). The spectral wave module was validated against Copernicus Marine Environment Monitoring Service (CMEMS) data, revealing that modeled significant wave heights (∼0.1–0.5 m) underestimated the satellite-derived wave height (CMEMS). Sediment transport calculations showed that cross-shore (onshore/offshore) transport processes dominated over longshore drift. The net longshore transport was minimal, and its direction varied seasonally. These results suggest that the Sariaya coast is in a dynamic equilibrium with very limited long-term erosion or accretion. The study demonstrates the value of the coupled 2DH-1D modeling approach in low-energy tropical settings. This work establishes a baseline for coastal infrastructure planning in Sariaya by confirming the coast’s present stability and highlighting the processes governing its morphodynamics. The approach provides a reliable tool for shoreline prediction in data-limited coastal settings and highlights the critical role of cross-shore processes, which are often neglected in traditional models.