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All Journal Ecotrophic, Journal of Environmental Science ILMU KELAUTAN: Indonesian Journal of Marine Sciences Journal of Environment INTERNATIONAL JOURNAL OF ENVIRONMENT AND GEOSCIENCES
Takahiro Osawa
CReSOS Unud
Agriculture, Biological Sciences & Forestry Earth & Planetary Sciences Environmental Science

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Monitoring of Merapi Volcano Deformation Using Interferometry Synthetic Aperture Radar (InSAR) Technique Pamungkas, Ayu Margaworo; Osawa, Takahiro; Adnyana, I Wayan Sandi
Journal of Environment Vol 1 No 1
Publisher : Graduate Study of Environmental Sciences, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

The Merapi volcano is the most active volcano in Indonesia until now, because of eruption occur every two or five years. To minimize the impact of volcanic eruptions need to monitor the volcanic activity, one effort in monitoring is to monitor the surface changes (deformation) around the volcano. These surface changes can be monitored with InSAR technique. In this study monitoring by analyzing the Digital Elevation Model (DEM) and displacement map from result processing using InSAR technique. The accuracy of DEM compare with Shuttle Radar Topography Mission (SRTM) DEM. These results showed that after the eruption in 2006 led to the deflation that occurred in 2007. In 2010 after the eruption led to deflation in some areas of Merapi volcano. Whereas in 2008 due to the absence of volcanic activity that occurred then the deformation is not so large changing. Test on the DEM from the process of InSAR compare with SRTM DEM produced an accuracy of 96%.
Monitoring Total Suspended Solid Distribution In Coastal Bali Area Using MODIS Satellite Data Ippah, Imro’atul; Osawa, Takahiro; Nuarsa, I Wayan
International Journal of Environment and Geosciences Vol 5 No 1 (2024): International Journal of Environment and Geosciences
Publisher : Graduate Study of Environmental Sciences, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/ijeg.2024.v05.i01.p04

Abstract

Total Suspended Solid (TSS) is one important parameter for water quality. This research aims to analyze MODIS feasibility for identifying TSS, to identify TSS monthly patterns and annual patterns variability, and to analyze the TSS distribution patterns around Bali coastal area. Observation data of the wet season was observed in Benoa Bay on 2nd October 2013 and the dry season was observed in Perancak from July on 28th to July 31st, 2009. The comparison between observation data and satellite data was used to establish a new modification algorithm for suitable conditions around Bali coastal area. Based on research analysis, the feasibility of MODIS was different in each season. In the wet season, the coefficient correlation was (r) = 0.55 and in the dry season, it was (r) = 0.68. poor correlation in the wet season indicated the bottom effect of the area which has a shallow and heterogeneous depth. The TSS average in the wet season was 75.55 mg/l and 55.97 mg/l in the dry season. The highest value was analyzed in November (82.74 mg/l) and the lowest value in June (46.41 mg/l). During wet season, the stream volume and the stream flow rate increase and bring the TSS into coastal areas through the runoff process. The mapping patterns showed that the southern coastal area and western coastal area of Bali had a high value every month. The northern coastal had a high value only in the wet season. The characteristic of Bali river area, which is perennial and intermittent rivers caused this phenomenon. The population and Bali land-use area also affected the high TSS in these areas. Yearly patterns of TSS from 2009 to 2013 around Bali coastal areas were different every year. The highest TSS distribution observed in 2013 wet season is 87.75 mg/l. The lowest TSS distribution occurred in 2009 dry season with a value of 52.2 mg/l. The TSS tends to increase every year due to the changing in Bali land use. TSS patterns from 2009 to 2013 were dynamic every year. The El Nina and La Nino events also gave impact on the patterns. The MODIS feasibility in different locations was different depending on the characteristic of the physical property of water. The shallow and small area causes misinterpretation of the satellite reflectance. The TSS monthly patterns depended on the season and the mapping can be used to describe the sources of TSS pollution, the distribution, and the quantity of TSS in the coastal area.
Internal solitary waves observation and feature extraction based on wavelet transform by Sentinel-1A in Lombok Strait, Indonesia Chonnaniyah, Chonnaniyah; Osawa, Takahiro; Karang, I Wayan Gede Astawa
International Journal of Environment and Geosciences Vol 5 No 1 (2024): International Journal of Environment and Geosciences
Publisher : Graduate Study of Environmental Sciences, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/ijeg.2024.v05.i01.p05

Abstract

Lombok Strait is an essential pathway in trans-oceanic water mass transport. Due to this water mass transport flowing over Indonesian waters, the current is known as Indonesian Throughflow (ITF), which plays a role in the transfer of warm water masses from the Pacific to the Indian Ocean annually. Lombok Strait has intensive characteristics of the internal waves (IWs) generation because of the strong current that passes through the complex bathymetry along the strait area. IWs with large amplitude and nonlinear properties are known as Internal Solitary Waves (ISW) that can be detected by Synthetic Aperture Radar (SAR) images. A Wavelet Transform method for ISW feature extraction was applied to SAR images by Sentinel-1A (C-band). ISW packet characteristics can be distinguished from other phenomena based on their geometrical structure and shape. ISW packet pattern consists of light and dark lines which decrease intensity from front to rear. SAR observation detected 5 parameters (phase speed, soliton numbers, wavelength, first crest length, and propagation direction). The arc-like ISW in the Lombok Strait propagated to the North of the sill with average phase speeds of about 2.13 m/s and was frequently detected during the northwest monsoon (NWM). The detected soliton number is less than 6 solitons per packet with a wavelength of about 1 – 4 km, and the first crest length varies from about 12.16 km to more than 100 km. ISW detected in Sentinel-1A images were located at the bathymetry about 800 meters around the Lombok Strait area.
Inherent Optical Properties Attenuation Coefficient Modelling for Optical Shallow Water in Kepulauan Seribu of Jakarta, Indonesia Setiawan, Kuncoro Teguh; Rosid, Mohammad Syamsu; Manessa, Masita Dwi Mandini; Suardana, A.A. Md. Ananda Putra; Adi, Novi Susetyo; Winarso, Gathot; Osawa, Takahiro; Asriningrum, Wikanti; Supardjo, Harsono
ILMU KELAUTAN: Indonesian Journal of Marine Sciences Vol 29, No 2 (2024): Ilmu Kelautan
Publisher : Marine Science Department Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ik.ijms.29.2.222-232

Abstract

Technology to obtain bathymetric information has become necessary considering the length of the coastline and the many islands owned by Indonesia. Measurement technology using multi-beam and single-beam echo sounders is still an alternative to producing bathymetric information. In shallow water, using echo sounders has constraints and limitations, such as being time-consuming, costly and prone to equipment damage. Remote sensing technology is an alternative to obtaining bathymetric information in shallow waters. Bathymetric modelling with analytical and semi-analytic models from satellites requires attenuation coefficients. Therefore, attenuation coefficient models are essential for satellite data. Attenuation coefficient studies using inherent optical properties (IOP) parameters have not yet been studied to determine Kepulauan Seribu bathymetry, Jakarta, Indonesia. The IOP modelling is determined by absorption and backscatter parameters. Chlorophyll-a Total influences these parameters: Total Suspended Matter (TSM) and Coloured Dissolved Organic Matter (CDOM). This study was performed to determine the attenuation coefficient model using multispectral remote sensing in the Kepulauan Seribu and applied five approaches to determining the attenuation coefficient via IOP: the Gordon, Kirk, Morel, Lee and Simon models. The five models' IOP attenuation coefficient results were compared to the in-situ attenuation coefficient value and evaluated. The results of IOP attenuation coefficient modeling of multispectral remote sensing based on the condition of local water parameters is Kd(λ) = 1.4369 ((a(λ) + b(λ)) / Cos θ) + 0.072. based on the modified Gordon method, The modelling results were obtained with an accuracy of 0.98 determination coefficient (R2) and 0.029 Root Mean Square Error (RMSE).
OIL SPILL SIMULATION IN THE BALI STRAIT USING THE GNOME AND FVCOM MODELS ON EASTERLY SEASON Putu Hadi Wiguna, Pande; Hendrawan, I Gede; Osawa, Takahiro
ECOTROPHIC : Jurnal Ilmu Lingkungan (Journal of Environmental Science) Vol 17 No 2 (2023)
Publisher : Master Program of Environmental Science, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/EJES.2023.v17.i02.p10

Abstract

Among several forms of marine pollution, oil damages coastal ecosystems. Repeated reports of oil contamination in the marine environment can partly load with major shipping lines. The Ketapang-Gilimanuk crossing over the Bali Strait is Indonesia's second busiest ferry port after Merak-Bakauheni. The most congested shipping routes can carry a significant risk of environmental damage from an oil spill. Oil spill trajectory modelling is carried out to reduce the impact of this possible disaster. Therefore, the use of modelling to ascertain the route of the oil spill was considered. The oil leak path is simulated using the GNOME model. Two oil spill scenarios were used as input models. The chosen location is around the Ketapang Gilimanuk crossing, as well as the time of the easterly season. An ocean HF radar stationed in the Bali Strait verifies the accuracy of the current marine data generated by FVCOM. To see the pattern of the oil spill trajectory based on a ten days simulation, we combined the latest data from FVCOM with GNOME. To determine the ability of the model to predict the flow and trajectory of oil spills in the Bali Strait, this study try to analyze and interpret the oil spill trajectory from model and then validate the model results with satellite imagery. Keywords: Bali strait; oil spill; trajectory; GNOME; FVCOM; HF Radar
SPATIAL ANALYSIS OF LANDSLIDE POTENTIAL ON AGRICULTURE IN THE AYUNG WATERSHED, BALI PROVINCE Feronika, Feronika; Osawa, Takahiro; Merit, I Nyoman
ECOTROPHIC : Jurnal Ilmu Lingkungan (Journal of Environmental Science) Vol 17 No 2 (2023)
Publisher : Master Program of Environmental Science, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/EJES.2023.v17.i02.p06

Abstract

The Ayung Watershed is one of the watersheds with mountainous and hilly landscapes with potential landslides. This study aims to determine the potential level of landslide susceptibility and its effect on agricultural land use in the Ayung watershed. The method used to determine the potential for landslides is a weighting/scoring method by overlapping the parameters causing landslides, namely rainfall, slope, land use, landform, geological structure, and soil type. Determining the effect of landslide potential on agricultural land is done by overlapping the landslide potential map with land use. The data used includes BMKG monthly rainfall for 2015-2019, the slope of DEMNAS data for 2020, geological structure and landform 1:25,000 scale RBI map data for 2019, land use using Sentinel 2A data for 2020, and soil types in the form of spatial planning maps Province of Bali 1:25,000 scale in 2019. The results showed that landslides in the Ayung watershed were categorized as low potential to high potential. Classes with no landslide potential are widespread in the upstream and downstream areas of the watershed, covering an area of ??18,976.01 ha (60%), the low potential category covering 5,877.78 ha (19%), the medium potential category covering an area of ??3,208.76 ha (10%) and the low potential category covering an area of ??3,208.76 ha (10%) spread over the upstream and central parts of the watershed covering an area of ??3,528.55 ha (11%). The effect of landslides on agricultural land has a category from no potential to high potential. The category with no potential is widespread in the upstream watershed area of ??13,268.57 ha (66%), the low potential category is 3,268.57 ha (16%), the medium potential category is 1,782.31 ha (9%), and the high category is spread in the upstream and the middle of the watershed area of ??1,707.28 ha (9%). Keywords: Landslide; Watershed; Mapping; Agricultural land
RETRIEVAL OF SURFACE CURRENT FROM HIMAWARI-8 SEA SURFACE TEMPERATURE DATA AND PARTICLE IMAGE VELOCIMETRY METHOD Wati, Kadek Setiya; Osawa, Takahiro; Astawa Karang, I Wayan Gede
ECOTROPHIC : Jurnal Ilmu Lingkungan (Journal of Environmental Science) Vol 17 No 2 (2023)
Publisher : Master Program of Environmental Science, Postgraduate Program of Udayana University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/EJES.2023.v17.i02.p08

Abstract

As human activity occurs at the surface, which is influenced by surface currents, understanding surface currents is crucial. Ocean currents are not solely caused by wind, but also of other factors, such as sea surface temperature. To obtain surface current data, BMKG used HF radar installed in several places, including Flores Sea. This location is significant because it has large ports and heavy crossing traffic. This study aims to analyse surface current data retrieve from Himawari-8 SST data by applied PIV algorithm. Using the PIV algorithm, a cross-correlation plane is generated by comparing two identically sized interrogation windows obtained from successive images. On 5 December 2022 in the Flores Sea, Himawari-8 SST data was employed to estimate sea surface currents every 10 minutes. Surface current motion varies widely from image to image. Western areas are dominated by westward currents, while central and eastern areas are dominated by eastward currents during daylight hours, and westward currents during the night. Synoptic wind affects surface current movement during those hours. Validation with observational data from the Labuan Bajo HF radar shows that the V component current estimation is better than the U component current estimation. This is particularly prevalent in the south and in areas close to the KAWA radar HF location. Keywords: Flores Sea; SST; Himawari-8; PIV; surface current
Co-Authors Ayu Margaworo Pamungkas Chonnaniyah, Chonnaniyah Dwi Puspa Arini Feronika, Feronika Gathot Winarso, Gathot I Gede Hendrawan I NYOMAN MERIT I Wayan Arthana I Wayan Gede Astawa Karang I Wayan Nuarsa I Wayan Sandi Adnyana Ippah, Imro’atul Kuncoro Teguh Setiawan, Kuncoro Teguh MASITA DWI MANDINI MANESSA, MASITA DWI MANDINI Novi Susetyo Adi, Novi Susetyo Putu Hadi Wiguna, Pande Rosid, Mohammad Syamsu Suardana, A.A. Md. Ananda Putra Supardjo, Harsono Wati, Kadek Setiya Wikanti Asriningrum, Wikanti