Analisis Penurunan Muka Tanah (Land Subsidence) Kota Semarang Menggunakan Citra Sentinel-1 Berdasarkan Metode Dinsar Pada Perangkat Lunak Snap

Abstract

Semarang city is the capital of Central Java province that is experiencing growth and rapid urban growth. However, based on its geological condition, Semarang City is formed by young alluvial deposits in which still allows the compaction that can cause land subsidence. In addition, groundwater extraction also contributed in the process of land subsidence in the Semarang City. To minimize its damage, land subsidence monitoring is required as a part of natural disaster mitigation. One of methods to monitoring land subsidence is by utilize Synthetic Aperture Radar (SAR) satellite image which is used in this research.The purpose of this research is to estimate the land subsidence in Semarang city using DInSAR method. This method is selected because of the ability to assess a wide area in a short time. The data used is 3 images Sentinel-1a level 1 which acquired between years 2015-2016. DInSAR method using two-pass interferometry with the Shuttle Radar Topography Mission (SRTM) 30 m as a reference to the topography. DInSAR is processed using SNAP open-source software.From this study, the average value of subsidence of Semarang City is 4,37±4 cm/year. The highest average subsidence is located in Sub-district Genuk, Pedurungan and North Semarang which each subsidence value is 10,35±1,02 cm/year, 8,31±2,36 cm/year and 8,23±1,58 cm/year. To know the DInSAR result\u27s accuracy, GPS measurement is used to validate which resulted standard deviation of 1,9 cm. From the results of this study also found a correlation between subsidence with tidal inundation and stratigraphy composition. Correlation with the tidal inundation was shown by the expansion of tidal inundation in areas which experiencing the highest subsidence in Semarang City. The correlation of the stratigraphic composition is clearly visible on alluvial areas, where the pattern of subsidence that occurred tend to follow the alluvial pattern which has higher subsidence value than areas to the other stratigraphic composition