Transport of estuarine sediment have a highly complex method, which is the combined effects result of periodically reciprocating flow, ocean waves, and the electrochemical characteristic of sea water [1]. Settling velocity (SV) is such a parameter fundamental for sediment researchers so that its accurate resolution has been regarded as a top priority in correcting modelling numerical and conceptual understanding of fine sediment dynamics [2] [3]. The goal of this study is to analyze the effect of salinity levels on the settling velocity of fine sediment grains in the Ciliwung estuary, Jakarta. The method used is direct measurement using the hydrometer analysis method. The result of experiment shows salinity levels affect the settling velocity of fine sediment grains in the Ciliwung estuary. The higher salinity, more faster the settling velocity of fine sediment grains. The average settling velocity at distilled water salinity 0 ppt is 1.083 mm/minute, sea water with salinity 0.3 ppt is 1.537 mm/minute, and sea water with salinity of 0.6 ppt of 1.561 mm/minute.

Water pollution problem in Jakarta has been going on for a long time. The existence of some rivers that are not directly connected to upstream in the tidal area can speed up the occurrence of water pollution and slow the circulation of polluted waste that affects water quality in river-estuary. Since 2010 after Kanal Banjir Timur (KBT) operated, Sunter River streamflow was divided by KBT, changes flow rate and water quality pattern. The study area is the main channel of the Sunter River which has 17 km lengths includes Duren Sawit, Pulo Gadung, Kelapa Gading, Plumpang, Rawa Badak and Tanjung Priok Area where the average water load is 624 mg/L. The simulation is divided into 2 scenarios with a flowrate configuration of 5 m3/s and 100 m3/s (with a raining condition of 1 hour). MuQuald3D, a three-dimensional water quality model, has been employed in this research. The merit of this model is that it can accurately predict water pollution load within the surface layer and the bottom layer and can be shown in contour profile which is effective and efficient guidance to solve the water quality problems along Sunter river-estuary. The model results show the effect of salinity will gradually reduce BOD concentration, and the existence of permanent construction around estuary (breakwater, port) changes pollutant distribution to the West and East area and increases the time of decomposition in waters, especially in low flowrate conditions.

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