Since 2014 sedimentation at the estuary of Jelitik river, Sungailiat, Bangka has continued to increase. At this estuary, the ship traffic is very busy and there is National Fisheries Port Sungailiat. When the tide is low, the river mouth closes thus disrupting ship traffic. The Bangka Belitung Provincial Government is currently planning to build a sediment control infrastructure to reduce the sedimentation rate. To plan and determine the effectiveness of the jetties requires knowledge of sedimentation patterns around Jelitik estuary. Therefore this study was conducted to determine the pattern of sedimentation (distribution and rate) at the existing and ultimate conditions. The methods are field survey, analysis of field data, and computational modeling of sediment transport. Modeling of sediment transport was done using the Sand Transport Module of MIKE 21. Two scenarios were simulated for the existing and ultimate conditions. Based on this modeling, the sedimentation rate at Jelitik estuary is found uneven. In the existing condition, a large rate of sedimentation occurs on the southern side of the Jelitik River estuary, which reaches a maximum value of 2.75 m/year, with an average of 4.44 cm/year. Whereas in the ultimate condition, the sedimentation rate decreases to 0.0377 m/year.

This research aims to analyze and estimate the amount of marine litter which get into seawater intake of PT Trans-Pacific Petrochemical Indonesia (TPPI) Tuban in existing conditions during west monsoon and east monsoon. Ten designs will be simulated to reduce and trap the marine debris entering the seawater intake (SWI). These designs will be tested for their effectiveness in reducing the number of debris entering the SWI using the particle tracking module of MIKE 21 numerical modelling package. The required data in this simulation are wind (speed and direction), wave (significant height, direction and period), the bathymetry of and coastline. Besides, this simulation is conducted based on primary data provided by TPPI Tuban management as the validation data. Based on the simulation results, the amount of marine litter entering SWI in the west monsoon is greater than the east monsoon, which is 349.14 kg/year for west monsoon and 100.84 kg/year for east monsoon. Based on the simulation results using the particle tracking module, it was found that design 5 is the most effective design, with the effectiveness of 73.97%. The biggest accumulation of marine litter using construction design 5 occurred in November, which was 355.36 kg.

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Currently, the central government and provincial governments of Bali and West Nusa Tenggara are promoting tourism development in North Bali and North Lombok. In the development of tourism, besides consider the potential of existing tourism objects, the economy, and its supporting facilities, the potential threats of disasters must also be considered. Based on historical records, one of the potential disasters in northern Bali and Lombok is a tsunami. This study aims to determine the height and the arrival time of the tsunami along the northern coasts of Bali and Lombok. This study was carried out by simulation and numerical modeling, using the TUNAMI Model. Modeling was carried out for 2 hypothetical scenarios caused by an earthquake from the Flores Back-arc Thrust. Base on this model, it is known that the height of tsunami on Trawangan Island is ± 6 m with an arrival time of ± 3 minutes, while on the north coast of Bali the height of the tsunami is ± 0.6 m with an arrival time of ± 21 minutes. The arrival times of the tsunami on the north coast of Bali and Lombok are so fast.