We studied land subsidence occurrence in Surabaya, considering the rapid urban growth in the city. It is evidenced by the increasing number of buildings (e.g., houses, apartments, offices) that have been realized before 2015 and the increasing transport activities in the industrial area. Land subsidence is a vertical deformation on the land surface that can be caused by landslides, earthquakes, soil consolidation process, or even human-made activities, depending on the material characteristics of the area. In this study, Time-series InSAR (TS-InSAR), specifically the Small Baseline Subset (SBAS) method, is applied to obtain the Line-of-Sight (LOS) velocities and time-series LOS displacements in Surabaya between May 2015 and September 2017. We used 28 Sentinel-1A data (IW mode) acquired by using Terrain Observation with Progressive Scan (TOPS) operation with the spatial resolution of 5 ´ 20 m and covers the area of 250 km2. DEM SRTM with 30 m spatial resolution was used to reduce topography effect contribution in the interferograms. Based on the SBAS method, interferogram pair selection is applied with the maximum value of 150 m for the perpendicular baseline and 100 days for the temporal baseline. The DInSAR process successfully generated seventy-four (74) interferogram pairs, and then by using SBAS algorithm, the LOS velocity and time-series LOS displacement were estimated. The results showed the varying displacements respond with the significant subsidence occurred in the North, East, and Southeast part of Surabaya. The SBAS result confirmed that the LOS velocity over the Surabaya area between May 2015 and September 2017 ranges from -40 to +30 mm/year. Significant land subsidence occurred in the Asemrowo area (North Surabaya) with the value of LOS displacement velocity up to -45 mm/yr.

Surabaya’s geological condition that dominated by alluvium unconsolidated, as well as increasing growth of buildings-especially skyscrapers-are triggered the surface deformation on the area. This research aims to monitor and analyze the surface deformation, especially the subsidence that occurred in Surabaya urban area over the last two years. We use Remote Sensing Technology that has been widely developed, not only aims to observe and analyze objects on the earth, but also very useful to monitor land surface changes. Interferometric Synthetic Aperture Radar (InSAR) is the first known technique to get surface deformation measurement effectively on large areas (thousands of km²) up to sub-centimeters. However, the technique also has limitations. In order to overcome the limitations of InSAR, multi-temporal InSAR techniques have been recently developed and one of them is Small Baseline Subset (SBAS). This time-series technique tries to overcome the temporal decorrelation due to atmosphere effect and measure transient movement on the Earth surface by using multi-look interferograms combination and small baseline temporal selection. Using SBAS technique we processed 24 Sentinel-1A images from Mei 2015 to Mei 2017 and 28 Sentinel-1A images from May 2015 to September 2017 to extract information of vertical displacement in Surabaya and compare both of them. The result shows that during the observation period, the rate of deformation in the form of Line of Sight Displacement (LOS) is varies from −60mm/year to +20mm/year. The majority of subsidence occured in coastal area (Northern and Eastern part) whereas the majority of uplift occured in the Surabaya downtown area (Southern and Western part).

Lapindo mud thrown to Porong River from September 27, 2006 brought an enormous impact to the environment and surrounding communities. This will exacerbate the damage Porong ecosystems, and pollute the Madura Strait and surrounding areas (Wibisono, 2006). Disposal of sludge in large quantities and continuously to Porong also indicated sedimentation resulted in Porong River, Porong River estuary and along coastal of Surabaya-Pasuruan. This is because the material sediment transport along water flow, and the influence of geographical conditions, and the waves of the sea water. Satellite image data used in this study is the ASTER in 2005-2008, ALOS/AVNIR-2 in 2010, and SPOT-4 years 2009.2011 and 2012. In the satellite image processing, for obtain the value of is used TSS algorithm of Jing Li (2008) for ASTER satellite imagery, algorithms of Hendrawan and Asai (2008) for the ALOS satellite imagery, and algorithm of Budiman (2004) for the SPOT-4 satellite imagery. TSS value of the image processing results then performed validation / test precision using reference data TSS In-Situ to obtain linear correlation (R2). R2 value was obtained is 0.854 in 2009, 0.761 in 2011, and 0712 in 2013. That indicates that the value of TSS in the field is proportional with the TSS value in image and has a very good correlation. The results show the value of TSS in the study area ranged from 25 until more than 150 mg/L and according to the results of the analysis showed an upward trend of TSS values over time. There are several locations that indicated experiencing severe sedimentation impacts such as in Porong River, Porong River Estuary, Alo River Estuary, and the surrounding area of the estuary. According to Government Regulation Number 82 in 2001, the maximum value of TSS in the river or water is must less than 50 mg/L and so the value of TSS in the study area is very improper that if allowed to continue may damage the ecosystem in the area. Results from this study is expected to be referenced in the rehabilitation, development, and utilization of the area in the research area and coastal zone management in the future.

Pemanasan global merupakan isu lingkungan yang menjadi tantangan besar bagi segala sektor. Salah satu sektor yang menyumbang emisi gas rumah kaca yaitu sektor industri migas salah satunya yaitu industri migas distribusi. PT Pertamina (Persero) DPPU Pattimura, Ambon merupakan salah satu industri yang menggunakan bahan bakar solar sebagai bahan bakar refueller. Penggunaan bahan bakar solar akan menghasilkan emisi CO₂ atau gas rumah kaca yang terlepas ke udara semakin tinggi. PT Pertamina (Persero) DPPU Pattimura, Ambon melakukan program untuk mengkonversi bahan bakar solar menjadi biosolar. Oleh karena itu, untuk mengetahui keberhasilan program tersebut penelitian ini ditujukan untuk membandingkan beban emisi CO₂, intensitas emisi CO₂ antara penggunaan solar dengan biosolar dan menghitung penurunan emisi CO₂ dari proses penyaluran avtur menggunakan refueller. Perthitungan emisi CO₂ berdasarkan IPCC 2006 menggunakan data jenis bahan bakar, jumlah penggunaan bahan bakar, dan faktor emisi bahan bakar. Perhitungan intensitas emisi CO₂ menggunakan data perhitungan beban emisi CO₂ dan jumlah avtur yang disalurkan. Penurunan emisi CO₂ menggunakan dua skenario sebelum dan setelah program konversi bahan bakar. Hasil yang didapatkan yaitu konversi bahan bakar menjadi biodiesel mampu menurunkan emisi CO₂. Intensitas emisi CO₂ menggunakan biosolar lebih rendah dibangingkan dengan solar. Penggunaan bahan bakar biosolar mampu menurunkan emisi CO₂ berturut-turut sebesar 19,467; 20,150; dan 12,408 Ton pada tahun 2017, 2018, dan 2019.