Shallow water hydrodynamics and tracer transport in Johor River Estuary

Malaysian coastal development posed a high pressure on the water quality and aquatic ecosystem. The planning for the construction of a tidal barrage across Johor River in Kota Tinggi is to prevent saline intrusion from reaching the Johor River Waterworks (JR WW) and also the large reclamation at Tekong Island, Singapore are expected to alter the hydrodynamics in Johor River Estuary (JRE) and East Tebrau Strait (ETS). The coupled effect of the two developments is likely to affect the advection and diffusion of pollutant in the area, which is important not only for navigation but also fishery and aquaculture. The flow field is simulated using shallow water model and validated against the tidal water level at JUPEM tidal station 48484 at Jeti Kastam, Johor Bahru. Results show excellent agreement in water level fluctuation and the simulated velocities at selected sampling location also agree well with observation. It is thus concluded that the numerical model realistically represent the actual hydrodynamics of JRE, include the ETS region. For the three scenarios considered, it is shown that there are changes in velocity due to reclamation at Tekong Island causes the channel width on its side to become narrower and causes the flow to accelerate around the island (significantly) In addition, construction the tidal barrage at Kota Tinggi cause discharge into JRE to reduce and consequently, the flushing rate of the estuary is reduced. For the study of tracer transport, the method of Lagrangian particle tracking is used to simulate the advection of passive tracers in the domain. The trajectories are analysis to identify the escape rate and resident time.