Hydrodynamics modeling with MIKE system in the Semak Daun Lagoon, Seribu Islands Indonesia

Abstract

At low tide condition, the Semak Daun Lagoon (SDL) barrier reef is drowned during high tide and appeared to the surface during low tide. How are hydrodynamics in low tide and tidal conditions? This study aims to examine the pattern and current velocity in the SDL under four tidal conditions. The two-dimension model is built based on two motion generations namely wind pressure and tides. The discretization of the equation uses the finite volume method. Domain discretization is divided into 14,575 triangular elements with a grid area of 1,000 m2. The results of the model, verified with observational data in the field, show the similarity of tidal patterns and current velocity as indicated by the MAPE value of 7.9%, meaning that the model is well constructed. Current patterns generally move from southwest to northeast at high tide to low tide condition and vice versa at low tide to high tide condition. At low tide, there is a buildup of water mass in the lagoon because the only channel north is functioning as an outlet. This causes a slowing of current flow inside the lagoon and acceleration in the northern canal. Current velocity ranges from 0.02-0.51 m.s-1. The pattern and speed of the current in the lagoon are dominantly influenced by tidal dynamics. Residual current velocity varies in the range of 0.01-0.04 m.s-1.