It is important to understand the sediment transport processes around port facilities, especially for minimizing siltation in navigation channels. Sedimentary processes are often due to several site-specific parameters, such as weather and maritime conditions and sediment properties. In this study, the targeted site is the Patimban coast on the north coast of west Java in Indonesia, where a new port is under construction, and field measurements were carried out to elucidate the supply process of fine sediments through the Cipunagara river, which flows into the coastal area.
　Considering the characteristics of climate with seasonal monsoons in the tropical rainforest area, field surveys such as water quality measurement were carried out in the rainy season and the dry season. In addition to the data acquisition of seasonal fluctuations in salinity and turbidity through the water column around the estuary, the in-situ measurement for the bulk density of the near bottom deposits to detect the fluid mud transportation. The field observations were carried out in February (the local rainy season) and August (the same dry season) of 2017, with the cooperation of the Agency for the Assessment and Application of Technology (BPPT), under the joint research project. The observed data shows the apparent difference in salinity and turbidity distributions between the rainy and dry seasons around the area, corresponding to the seasonal change in the freshwater and sediment discharge through the river. Furthermore, in the rainy season, the existence of a fluid mud layer with the thickness of about 15 cm was detected by using an in-situ densimeter.

Key Words: Java Sea, Monsoon, Field monitoring, Fine sediments, Fluid mud