Spatial information on the rate of subsidence in North Coastal Area of Java and the estimation of inundation in 2031

Abstract

North Coastal Java Java is a fast-growing area because many big cities such as Jakarta, Cirebon, Pekalongan, Semarang, and Surabaya exist. This area is experiencing several environmental problems, the biggest of which is the problem of the rate of land subsidence. This problem is due to the geological structure. The Java Coast is located on soft soil, and some groundwater utilization activities are less controlled. This study aimed at (1) Obtaining information on the rate of land subsidence in 5 major cities on the northern coast of Java (Jakarta, Cirebon, Pekalongan, Semarang, and Surabaya) using remote sensing satellite data; (2) Analysing the accuracy of land subsidence using field survey data; (3) Estimating the potential of the region to be below 0 masl in 2031; and (4) Analysing the causes of land subsidence. The method used was Difference Interferometry Synthetic Aperture Radar (DInSAR) to determine the rate of land subsidence and simulate the rate of land subsidence in the future. The results showed that the rate of land subsidence in Jakarta (8/year), Cirebon (2 cm/year), Pekalongan (11.2 cm/year), Semarang (6 cm/year), and Surabaya (4.3 cm/year). The results of the research show that the error rate of the surface subsidence rate with validation results in the City of Jakarta is ± 0.01 m. with the value of Nash Sutcliffe Efficiency (NSE) =. 0.787 with a good category. Simulation results in 2031 from 3 big cities show that the area under 0 masl will increase by 2710 ha (Jakarta), 3565 ha (Pekalongan), and 846 ha (Semarang) from 2021. It seems that Pekalongan needs special attention to deal with the rate of land subsidence compared to other cities.