Abstract. Knowledge of the actual condition of hydrodynamics in the nearshore and coastal area is essential for coastal monitoring activities. To this end, a coastal operational model system can serve as a tool in providing recent and up-to-date, state-of-the-art hydrodynamics along the coast. In this paper, we apply CoSMoS (Coastal Storm Modeling System), a generic operational wave and tide-surge modelling system applied here to predict waves and water levels along the Dutch coast. The CoSMoS application is not limited to storm impact prediction on the Dutch coast, but can also be applied to other coastal hazards such as rip currents and coastal flooding, in other environments. In this paper, we present the set-up of the CoSMoS system and a validation of the wave and surge model, with deep-water wave buoy data and tidal gauge measurements as ground truth validation material. The evaluation is presented as monthly error measures between computed parameters and observed ones. Hindcast results over the whole year of 2009 show that the simulated wave parameters and surge elevation from the CoSMoS are in good agreement with data, with average root mean square (rms) error over the year of 0.14 m for the surge elevation and 0.24 m for the significant wave height. It is noted that there is a tendency of the wave model to underestimate the height of northerly waves with lower frequencies (swell). Additionally, when a wave separation algorithm is applied on the overall spectrum, results show consistent underestimation of the swell component by the model, which for the Dutch coast will mainly come from the north, where the North Sea is open to the Atlantic Ocean. In the proposed model system, the swell boundary can have a significant effect on the simulated wave results, suggesting room for improvement for the swell boundary conditions to the north and the swell propagation within the Dutch Continental Shelf Model. Finally, we show that in forecast mode, CoSMoS can provide reasonably good wave and surge prediction.

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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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