Mangrove density impacts on tidal dynamic in Segara Anakan Lagoon, Indonesia

Abstract

The present study aims to understand the tidal dynamics in a tropical coastal lagoon, Segara Anakan, Java, Indonesia. It is a shallow lagoon, with complex tidal channels and connected to the Indian Ocean by two channel outlets. It covers an overall area of about 12.000 ha. Three-quarters of the lagoons area have mangroves and the remaining quarter is covered by water. The Delft3D model has been implemented and validated using observation data. Scenario with uniform and spatially bottom drag coefficient were created in order to investigate the influence of the mangrove density on tidal dynamics. Based on tidal harmonic analysis, the M2 amplitude attenuates from both the western and the eastern lagoon inlets to the interior of the lagoon as the tidal wave is constricted by the narrow lagoon inlet and shallowness of the lagoon. For the case of uniform mangrove density, tidal harmonic analysis reveals M2 amplitude decreasing of 0.5 to 0.25 m from lagoon inlets toward central lagoon due to bottom friction effect. The tidal propagation into lagoon show increasing M2 tidal phase with maximum delay of 2.5 hours at the central lagoon. For the case of spatially mangrove density, the dampening of the tidal wave is stronger of 18% and the phase delay is longer 0.8 hours compare to the case of uniform mangrove density.