NUMERICAL SIMULATION OF COHESIVE SEDIMENT TRANSPORT IN JAKARTA BAY

The 3D-numerical model has been applied to simulate the current circulation and cohesive sediment transport in the Jakarta Bay, Indonesia. Sediment load comes from 3 river mouths i.e. Angke River, Karang River, and Ancol River. The model was simulated to analyze the effect of tidal current and river discharge. A constant westerly and easterly wind was used as input of the model to see the influence of monsoonal season. The numerical result showed that the tidal current flows from east to western part of the bay during ebb tide and vice versa during flood tide. The surface current circulation was dominantlyinfluenced by the tidal current comparated with the wind and river discharge effects. Hight turbidity level was found near the river mounths with the range of 50 to 100 mg per l. This high in the offshore area of the bay the sediment concentration decreases up to 10 mg per l. The movement of sediments followed the current circulations. During the flood tide, the sediment concentratation from the mounth of Angke River moved to the western part of the bay. Model simulated for increasing the river discharge into two times showed that the sediment distributed to the offshore direction two time longer compare with the normal debit. The transport of sediment from the Angke and Karang Rivers to the offshore area reached up to 6 km, while it just reached plus minus 2,5 km from the Ancol River. Keyword: Numerical model, Cohesive sediment, Effect of tidal current and river discharge.

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ANALISIS SEDIMENTASI LAGUNA SEGARA ANAKAN DENGAN PEMODELAN NUMERIK ANGKUTAN SEDIMEN KOHESIF

Jurnal Teknik Hidraulik ◽

10.32679/jth.v12i1.642 ◽

2021 ◽

Vol 12 (1) ◽

pp. 1-14

Author(s):

Irham Adrie Hakiki ◽

Leo Eliasta Sembiring ◽

Cahyo Nur Rahmat Nugroho

Keyword(s):

Sediment Transport ◽

Numerical Model ◽

Transport Model ◽

Factor Model ◽

Cohesive Sediment ◽

Analysis Model ◽

Sediment Volume ◽

Cohesive Sediment Transport ◽

Speed Up ◽

One Year

Sagara Anakan Lagoon has been continuously receded caused by the high sedimentation rate. The deposited sediment volume was predicted to be around 1 million m3/year. This phenomenon, if not treated will harm the existing ecosystem and also could cause many kinds of its native biota extinct. Engineering could be applied to prevent it. However, the transport and sedimentation pattern must be known for it to be effective. Silting in Sagara Anakan Lagoon simulated by using MIKE21 numerical model which could simulate sediment transport in 2D horizontal scheme. The deposited sediment, mainly consisted of mud, so the model must be capable for simulating cohesive sediment transport. Model is set to simulate one year of morphological event which reached with the usage of time speed up acceleration factor. Model calibrated to be able to simulate a deposition event in the order of one million m3/year. Model calibrated by tuning critical bed shear stress for deposition and erosion parameters as a base for sensitivity analysis. Model result shown that the sedimentation in Sagara Anakan Lagoon is caused by asymmetry of flood and ebb current. Major siltation happened around the delta with the maximum and mean observed bed change are approximately 0.6 m and 0.16 m respectively. The setup for this model could be used as a base model for planning an engineering approach for controlling sediment in Sagara Anakan Lagoon.Keywords: Numerical model, cohesive sediment, mud transport, estuary modellingKata Kunci: Model numerik, sedimen kohesif, transpor lumpur, pemodelan estuari

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