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The open resource materials are used in this research to construct a numerical model and study the tidal flood in Pekalongan City, including the impact of land subsidence. The area of interest is in 6 villages in the north coast of Pekalongan namely, Jeruksari, Pabean, Bandengan, Kandang Panjang, Panjang Baru, and Panjang Wetan. Delft3D, an open ware, is used for numerical modelling. While the input data are obtained from GEBCO for bathymetry, SRTM for topography, and TPXO for tidal constituent. The resulting model shows a decent agreement with field tidal elevation data from Indonesian Navy Tide Tables and GLOSS. After applying the annual land subsidence, compare to flood in May 2018, it is found that the inundation height increases for around 11, 36, and 132 cm in 2019, 2025, and 2050. In 2050, an extreme inundation over 2.5 m is found. Similar with Jakarta flood, to protect the land area, coastal dykes may be proposed. However, for long-term resilience, it is recommended to emphasize efforts in decreasing the land subsidence rate. This study indicates the threat of tidal flood in Pekalongan, thus further studies followed with field survey and more constituents in the modelling are strongly recommended.

Indonesia is currently intensively developing its renewable energy resource and targets at least 23% by 2025. As an archipelago country, Indonesia has the potential to benefit from its abundant renewable energy resources from its offshore regions. However, the short tidal range of mixed semi-diurnal and the suitable tidal turbine capacity may hinder marine renewable energy development in Indonesian waters. This paper presents higher-order hydrodynamic numerical models to provide spatial information for tidal current resource assessment of the Patinti Strait. The present study applied the hydrographic and oceanographic method to produce input of the numerical model. Based on the selected simulation analysis, the highest current speed could be identified around Sabatang and Saleh Kecil Island with up to 2.5 m/s in P1 and 1.7 m/s in P4. Besides, the operational hours for the two observation points are 69% and 74.5%, respectively. The results indicate that this location is of prime interest for tidal turbine implementation as an energy source, for medium capacity (300 kW) and high capacity (1 MW).

In the past years, Indonesian people put more attention to Sunda Strait located between Java and Sumatra Islands, one of the busiest straits occupied with residential, recreational, fisheries, transportation, industrial and mining activities. Previous works on numerical modelling of tidal flow hydrodynamics of the Sunda Strait have resulted in good agreement against field data; however, the calibration of the models used was not described in detail. This paper presents the process of setting up the model, extensive calibration, validation and prediction of tidal currents for the Sunda Strait. A two-dimensional tidal-driven model is constructed using Delft3D, an open-source developed by Deltares. Four different bathymetry datasets, four different boundary condition configurations, and various bed roughness values are used, and their suitability in predicting tidal water level and current are investigated. It is found that changing the bathymetry and boundary conditions improve the model validation significantly. GEBCO_2019 bathymetry dataset outperforms the Batnas, even though it has a coarser resolution. For boundary conditions, the combination of water level and current velocity results in a better validation compares to using water level or current velocity only. However, the bed roughness shows an insignificant influence in predicting tidal conditions. The averaged current velocity is lower at the Southern than the Northern side of the strait due to a larger cross-section, consequence of deeper water. High tidal currents of magnitude around 2 m.s-1 are seen at the bottleneck of the strait.

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