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Muhammad Ridwan Prananda
Journal of Engineering, Infrastructure and Geosciences (2026)
The north coast of Central Java is sinking faster than the sea is rising, and tidal (rob) flooding now disrupts Semarang, Demak and Pekalongan in ordinary weather. This structured narrative review collates subsidence rates measured by interferometric synthetic aperture radar (InSAR), Global Navigation Satellite System (GNSS) surveys and levelling, the drivers identified for them, and the engineering and planning responses in place or planned as of 2026. Searches of Crossref and the open web on 8 October 2026 returned 289 records; 44 were assessed in detail and 40 studies were included, 19 of which report measured rates. Published maxima range from about 10 cm/year (2002–2006) to 100–120 mm/year (2015–2022) and 144–146 mm/year (2020–2023) in Semarang–Demak, and from 3 cm/year to more than 20 cm/year in Pekalongan, where a continuous GNSS station records −107.0 mm/year. The spread reflects differences in statistic, reference frame, geometry, period and benchmark depth more than disagreement about the phenomenon. Groundwater abstraction dominates in Semarang and Pekalongan, whereas natural compaction contributes 0.9–2.2 cm/year in Demak. The review argues that sea dikes and polders without enforced groundwater control are a wasting asset, and proposes conditions for making coastal defence durable.