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All Journal Ecotrophic, Journal of Environmental Science ILMU KELAUTAN: Indonesian Journal of Marine Sciences Journal of Environment Jurnal Geografi INTERNATIONAL JOURNAL OF ENVIRONMENT AND GEOSCIENCES INDONESIAN JOURNAL OF URBAN AND ENVIRONMENTAL TECHNOLOGY
Takahiro Osawa
CReSOS Unud
Agriculture, Biological Sciences & Forestry Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Earth & Planetary Sciences Education Energy Environmental Science Social Sciences Other

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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
DETERMINATION OF BATTERY WASTE MANAGEMENT STRATEGY IN THE IMPLEMENTATION OF ELECTRIC MOTORCYCLES IN DENPASAR CITY Prasetyo, Otniel Stefen Adi; Sholihah, Qomariatus; Osawa, Takahiro; Pertiwi Jaya, Ni Made; Arbani, I Made Dwi
INDONESIAN JOURNAL OF URBAN AND ENVIRONMENTAL TECHNOLOGY VOLUME 6, NUMBER 2, OCTOBER 2023
Publisher : Universitas Trisakti

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25105/urbanenvirotech.v6i2.16834

Abstract

Electric two-wheelers are becoming increasingly popular in Indonesia, particularly in the city of Denpasar; due to government regulations and social action, programs growing the number of electric motorcycles will impact the generation of toxic and hazardous waste in the form of used batteries which can cause environmental pollution if not managed properly. In connection with the establishment of a lifecycle-based business ecosystem and reduction of pollution risks, the thing that needs serious attention is the development of independent battery waste management facilities in Denpasar City. Aim: In this regard, a study was conducted on the development and management strategy of used battery waste for electric motorcycles in Denpasar City. Methodology and Results: Data was analyzed on primary data collected through in-depth interviews with key persons and questionnaires and secondary data obtained from related institutions. The development strategy was directed at six indicators, i.e., economy, interest, infrastructure, media, technology, and battery waste management facilities. By considering the six strategy indicators, the location of battery waste management facilities from four sub-districts in Denpasar City was determined using the Analytic Hierarchy Process (AHP) method, where the South Denpasar Sub-district was obtained as the top priority with a value of 0.403. Conclusion, significance, and impact study: This strategy is expected to be a direction for implementing electric motorcycle vehicles in Denpasar City
Identification of Fault Zone in Bali Using GGMPlus Gravity and Alos-2 Palsar-2 Data Pratama, I Putu Dedy; Osawa, Takahiro; As-Syakur, Abd Rahman
JURNAL GEOGRAFI Vol. 15 No. 1 (2023): JURNAL GEOGRAFI
Publisher : Universitas Negeri Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24114/jg.v15i1.40772

Abstract

The local active fault in Bali has a small magnitude (M<5) but has destructive potential because it is very close to residential areas. Mapping the fault area on Bali is needed to identify the parameters of faults. This study used gravity data from GGMplus, topographic data from DEMNAS, and lineaments using ALOS-2 PALSAR-2 data. Validation and interpretation using the geological map of Bali and seismicity data. We interpret the subsurface using the gravity derivative method to identify the type of fault movement. Identify fault locations using lineament extraction from SAR data processed by directional filters. The composite image red-green-blue (RGB) for HH, HV, and VV polarization was used for automatic lineament extraction and then corrected manually. The results of the gravity method succeeded in identifying 29 of the 30 faults from the geological map of the Bali sheet and a new spot from PALSAR-2. Bali land has 12 thrust faults, 11 strike-slip faults and six normal faults. The image of PALSAR-2 (L band) has succeeded in making a fault lineament map for the Bali region. The lineament extraction results from PALSAR-2 obtained four new faults (Pesanggaran, Sepang, Tegal Badeng, and Banyuwedang), while four faults were not identified (Tampaksiring Fault, Plaga, Mambal, and Munduk-Rajasa). NE-SW dominates the strike directions, and the dip angles are 45-80 degrees. We propose 30 faults in Bali, including 26 defects from geological maps with changes in length and location shift and four new marks extracted from automatic lineament.Keywords: Remote Sensing, Earthquake, Derivative Gravity, Lineament, SAR 
Validation of Satellite Rainfall Product (GPM-IMERG) an Bali and Nusa Tenggara: A Comparison of Normal Seasons, El Nino and La Nina Events Tulistiawan, Putu Eka; Karang, I Wayan Gede Astawa; Osawa, Takahiro
JURNAL GEOGRAFI Vol. 15 No. 2 (2023): JURNAL GEOGRAFI
Publisher : Universitas Negeri Medan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24114/jg.v15i2.44967

Abstract

Bali and Nusa Tenggara are regions where monsoonal wind changes and strange interactions between the ocean and atmosphere influence rainfall. The purpose of this research is to evaluate Integrated Multi-Satellite Retrievals for GPM (IMERG) rainfall data using in-situ observations from Bali and Nusa Tenggara, Indonesia, while considering seasonal variations and the El Nino-Southern Oscillation (ENSO) phenomenon. The study combines rainfall data from synoptic stations with rain gauge measurements over ten years, from January 2012 to December 2021, to obtain more accurate verification results. The study's findings indicate that, apart from the transitional seasons, IMERG data provides substantial estimates of monthly rainfall accumulation with low error values for both light and heavy rainfall. The study also reveals that the islands' complexity and topography can impact each province's validation values. The verification results show excellent accuracy in flat terrain areas and moderate elevations, while performance decreases in regions with high altitudes. These findings are significant because IMERG data can estimate rainfall for regions lacking monitoring stations during specific seasons and active ENSO conditions. Thus, this information can serve as a valuable tool to address the issue of data unavailability in hard-to-access areas and contribute to optimizing water resource management and weather-related disaster mitigation. Keywords: Validation, Rainfall, IMERG, ENSO
Co-Authors Abd. Rahman As-syakur Arbani, I Made Dwi 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 Pertiwi Jaya, Ni Made Prasetyo, Otniel Stefen Adi Pratama, I Putu Dedy Putu Hadi Wiguna, Pande Rosid, Mohammad Syamsu Sholihah, Qomariatus Suardana, A.A. Md. Ananda Putra Supardjo, Harsono Tulistiawan, Putu Eka Wati, Kadek Setiya Wikanti Asriningrum, Wikanti