The Effects of Different Inlet Configurations on Particles Transport and Residence Time in a Shallow and Narrow Coastal Lagoon: A Numerical Based Investigation

Abstract

Setiu Lagoon experienced shoreline alterations, leading to the opening of a new inlet and the closing of the old one. To evaluate the effects of these alterations on the tidal flow in this shallow and narrow lagoon, a numerical hydrodynamic model was developed. The model-predicted water level and current velocities were validated against field measurements, which yielded a high simulation skill. The transport of particles and residence time under different inlet configurations were also investigated through the implementation of numerical tracers released from R1, R2, and R3, which represent different pollution sources. The results indicated that the particle transport and residence time in Setiu Lagoon varied spatially and temporally depending on the release locations, proximity to the inlet, and tidal current strength. Comparing the scenarios, the flushing efficiency in Setiu Lagoon was improved with the presence of both inlets, resulting in a shorter residence time of less than 50 days. The findings of this research are vital for understanding the water current flow and residence time in this restricted lagoon, while evaluating the possible adverse effects on its water quality. Although this work is case-study based, the output is applicable to other lagoon systems with similar characteristics.