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SEASONAL VARIATIONS OF NUTRIENT BUDGETS IN JAKARTA BAY, INDONESIA Nugrahadi, Mochamad Saleh; Yanagi, Tetsuo; Tejakusuma, Iwan G.; Aji, Seno; Darmawan, Rahmania A.
Marine Research in Indonesia Vol 35, No 1 (2010)
Publisher : Research Center for Oceanography - Indonesian Institute of Sciences (LIPI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14203/mri.v35i1.7

This study aims to quantify the fluxes of carbon, nitrogen, phosphorus, and silicate in Jakarta Bay and use these flux data to gain an initial understanding of the biogeochemical processes occurring in the system. We investigated water, suspended matter and sediments fluxes from estuarine, coastal water and outside of the bay. Water samples were analyzed for dissolved nutrients, chlorophyll-phytoplankton abundance, and their composition. Suspended matter and sediment were analyzed for carbon and nitrogen. Nutrient concentrations were high in the rivers or estuaries and then decreased rapidly seaward. Calculation budget results showed that Jakarta Bay is a sink for DIP, DIN and DSi during dry season and rainy season. In the dry season, the system is in the slightly fixation condition ([nfix-denit] = 0.03 mmol N m-2 d-1). In contrast, denitrification exceed nitrogen fixation ([nfix-denit] = -9.74 mmol N m-2 d-1) in the rainy season. Moreover, the bay produced net carbon about 2.6-32 mmol C m-2 d-1.

SEASONAL VARIATIONS OF NUTRIENT BUDGETS IN JAKARTA BAY, INDONESIA Nugrahadi, Mochamad Saleh; Yanagi, Tetsuo; Tejakusuma, Iwan G.; Aji, Seno; Darmawan, Rahmania A.
Marine Research in Indonesia Vol 35 No 1 (2010)
Publisher : Research Center for Oceanography - Indonesian Institute of Sciences (LIPI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14203/mri.v35i1.7

This study aims to quantify the fluxes of carbon, nitrogen, phosphorus, and silicate in Jakarta Bay and use these flux data to gain an initial understanding of the biogeochemical processes occurring in the system. We investigated water, suspended matter and sediments fluxes from estuarine, coastal water and outside of the bay. Water samples were analyzed for dissolved nutrients, chlorophyll-phytoplankton abundance, and their composition. Suspended matter and sediment were analyzed for carbon and nitrogen. Nutrient concentrations were high in the rivers or estuaries and then decreased rapidly seaward. Calculation budget results showed that Jakarta Bay is a sink for DIP, DIN and DSi during dry season and rainy season. In the dry season, the system is in the slightly fixation condition ([nfix-denit] = 0.03 mmol N m-2 d-1). In contrast, denitrification exceed nitrogen fixation ([nfix-denit] = -9.74 mmol N m-2 d-1) in the rainy season. Moreover, the bay produced net carbon about 2.6-32 mmol C m-2 d-1.

ANALISIS PASCA BENCANA TSUNAMI CIAMIS - CILACAP Tejakusuma, Iwan G.
Jurnal Sains dan Teknologi Indonesia Vol. 10 No. 2 (2008)
Publisher : Badan Pengkajian dan Penerapan Teknologi

Earthquake with magnitude 7,7 on the Richter scale happened on 17 July 2006 in Indian Ocean, south of Ciamis District at 10 kilometer depth. The earthquake has generated tsunami and causing disaster in the coastal areas of Ciamis – Cilacap.More than 500 people died and hundred of buildings were damage. Field investigations showed that inundation along the affected coastal areas of Ciamis – Cilacap depend on the coastal morphology. In the areas with sand ridges the inundation distance were reduced significantly for example only about 150 meter in Widarapayung compared to 500 meter to 1 kilometer in Pangandaran. Damage to buldings depend on the building constructions. Wooden buildings were easily swept away by the tsunami waves. Concrete buildings without reinforced were heavily or completely damage compared to more withstand reinforced concrete buildings.

PENGKAJIAN KERENTANAN FISIK UNTUK PENGEMBANGAN PESISIR WILAYAH KOTA MAKASSAR Tejakusuma, Iwan G.
Jurnal Sains dan Teknologi Indonesia Vol. 13 No. 2 (2011)
Publisher : Badan Pengkajian dan Penerapan Teknologi

Coastal Vulnerability Index (CVI) was used to analyse the physical vulnerability to coastal disaster of the coastal areas of Makassar City. CVI will consider six variables namely geology, geomorphology, erosion and accretion, tidal range, average wave height and elevation. Geologically, coastal areas of Makassar comprise sand, gravel, clay and coral limestone. Geomorphologically, alluvial plain, sandy to gravelly beaches are predominant in the coastal areas. Both erosion and accretion occurred in the coastal areas in which accretion predominantly found in the southern part whereas erosion in the northern part of the city. Using DigitalElevation Model it can be observed that the elevation of the coastal areas of Makassar City is between 0 – 0.5 meter which is very vulnerable to sea level rise. Average tidal range was between 1.1 to 2 meter and wave height between 0 to 2.9 meter. CVI analyses showed that the coastal areas of Makassar City is vulnerable to sea level rise and hence to the coastal disaster. In addition, according to the analyses, Wajo, Biringkanaya and Tamalanrea districts are very vulnerable to sealevel rise and coastal disaster. Coastal development planning in these veryvulnerable areas will need special attention and specific measures.

KADAR AIRTANAH PEMICU LONGSOR DESA GIRIMEKAR KABUPATEN BANDUNG PROVINSI JAWA BARAT Tejakusuma, Iwan G.
Jurnal Sains dan Teknologi Indonesia Vol. 15 No. 1 (2013)
Publisher : Badan Pengkajian dan Penerapan Teknologi

Bencana longsor makin sering terjadi di Indonesia dan telah banyak menyebabkan korban jiwa, kehilangan harta benda dan kerugian ekonomi. Di Kampung Legokhayam, Desa Girimekar, Kabupaten Bandung, Jawa Barat longsor terjadi pada 21 Maret 2010 menghancurkan 9 rumah dan 9 rumah lainnya rusak. Longsor tersebut dikontrol oleh faktor geologi – litologi dan kemiringan lereng dan terjadi dipicu oleh curah hujan.Tipe longsor adalah translasional dan sebagian kecil rotasional. Kadar airtanah diteliti untuk mengetahui ambang batas untuk longsor. Sampel tanah undisturbed dari lokasi BH 01 dan BH 02 diambil dan dianalisa di laboratorium untuk parameter index properties dan engineering properties. Analisis kestabilan lereng juga dilakukan dan disimulasikan untuk mengetahui kadar airtanah kritis untuk longsor. Hasilnya menunjukkan bahwa faktor keamanan lereng di BH 01 adalah 0,832 dan di BH 02 adalah 0.962. Nilai kritis airtanah untuk longsor adalah 90% untuk lapisan atas dan 76% untuk lapisan bawah di BH 01 dan 82% untuk lapisan bawah di BH 02. Longsor akan terjadi bila kandungan airtanah melebihi nilai tersebut. Nilai tersebut dapat digunakan untuk sistem peringatan dini longsor.

SEDIMENT AND SUSPENDED PARTICULATE MATTER OF JAKARTA BAY, INDONESIA Tejakusuma, Iwan G.; Adi, Seno; Nugrahadi, M.S; D., Rahmania; Yanagi, T.
Jurnal Air Indonesia Vol. 5 No. 2 (2009): Jurnal Air Indonesia
Publisher : Center for Environmental Technology

Jakarta Bay is a semi enclosed bay located in the northern coast of Jakarta Metropolitan City. Hydrologically 13 rivers flowing in the Jakarta region and there are three big rivers with significant discharge to the Jakarta Bay namely Citarum, Ciliwung, and Cisadane Rivers. Jakarta, as Indonesian capital city with population of 8.725.630 inhabitants, and another 15 million people live in the surrounded suburban of Jakarta, creates a significant anthropogenic impact to the environmental system. Limited infrastructures, such as no sewerage system and lack of industrial waste management, cause the rivers in this region have over their carrying capacity.Seventeen sampling stations were determined in the Jakarta Bay, consisting of 5 stations at the river mouths (estuaries) and other 12 stations in the bay spreading from the coastal to offshore areas. Water and sediment samples were taken during 2 monsoonal or seasonal variations, August 2006 for dry season and February 2007 for rainy season respectively. Additionally, samples were also taken in May 2007.Sediment distribution in the estuary consists mostly of black clay. The sediments clays were bad smell. In the coastal region and in the dry season, the sediments consists of black clay and at one sampling site (station S3) the sediment was bad smell. However, all sampling sites became bad smell in the rainy season. In the inner bay area, sediments were greyish green sandy clay with some shell fragments. In the outer bay, the sediments were dominated by greyish green clayey sand with some shell fragments. The black clay with bad smell is indicative of anthropogenic influence from Jakarta River Basin. C/N ratio of the sediments in the dry season ranged from 1 to about 4.2 where in the estuaries (at stations M1, M2 and M4) the ratio were higher compared to the inner and outer bays. The C/N ratio of suspended particulate matter ranged from the lowest ratio of 0.7 to the highest ratio of 17.7 at the bottom layer and lesser ranged of 0.7 to 9.8 at Ã‚Â surface layer. POC concentrations ranged between 50-650 Ã‚ÂµM and 50-900 Ã‚ÂµM, in February and May, respectively. High concentrations of POC exists along the coastline or estuaries then decreasing toward the sea. POC is distributed widely in February than that in May due to higher discharge from the rivers. The average TOC concentrations in February is lower than that in May, but the TOC load in February was much higher than that in May due to the big differences of river discharge and because the samples were taken a week after the big flood in Jakarta area (February 4th - 6th, 2007). Total organic carbon fluxes from the river to the bay in February and May 2007 were 107.6 T /day C and 42.7 T /day C, respectively.Ã‚Â Key words : sediment, anthropogenic influence, C/N Ratio, POC, TOC, flux

SEDIMENT AND SUSPENDED PARTICULATE MATTER OF JAKARTA BAY, INDONESIA Tejakusuma, Iwan G.; Adi, Seno; Nugrahadi, M.S; D., Rahmania; Yanagi, T.
Jurnal Air Indonesia Vol. 5 No. 2 (2009): Jurnal Air Indonesia
Publisher : Center for Environmental Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29122/jai.v5i2.2442

Jakarta Bay is a semi enclosed bay located in the northern coast of Jakarta Metropolitan City. Hydrologically 13 rivers flowing in the Jakarta region and there are three big rivers with significant discharge to the Jakarta Bay namely Citarum, Ciliwung, and Cisadane Rivers. Jakarta, as Indonesian capital city with population of 8.725.630 inhabitants, and another 15 million people live in the surrounded suburban of Jakarta, creates a significant anthropogenic impact to the environmental system. Limited infrastructures, such as no sewerage system and lack of industrial waste management, cause the rivers in this region have over their carrying capacity.Seventeen sampling stations were determined in the Jakarta Bay, consisting of 5 stations at the river mouths (estuaries) and other 12 stations in the bay spreading from the coastal to offshore areas. Water and sediment samples were taken during 2 monsoonal or seasonal variations, August 2006 for dry season and February 2007 for rainy season respectively. Additionally, samples were also taken in May 2007.Sediment distribution in the estuary consists mostly of black clay. The sediments clays were bad smell. In the coastal region and in the dry season, the sediments consists of black clay and at one sampling site (station S3) the sediment was bad smell. However, all sampling sites became bad smell in the rainy season. In the inner bay area, sediments were greyish green sandy clay with some shell fragments. In the outer bay, the sediments were dominated by greyish green clayey sand with some shell fragments. The black clay with bad smell is indicative of anthropogenic influence from Jakarta River Basin. C/N ratio of the sediments in the dry season ranged from 1 to about 4.2 where in the estuaries (at stations M1, M2 and M4) the ratio were higher compared to the inner and outer bays. The C/N ratio of suspended particulate matter ranged from the lowest ratio of 0.7 to the highest ratio of 17.7 at the bottom layer and lesser ranged of 0.7 to 9.8 at Ã‚Â surface layer. POC concentrations ranged between 50-650 Ã‚ÂµM and 50-900 Ã‚ÂµM, in February and May, respectively. High concentrations of POC exists along the coastline or estuaries then decreasing toward the sea. POC is distributed widely in February than that in May due to higher discharge from the rivers. The average TOC concentrations in February is lower than that in May, but the TOC load in February was much higher than that in May due to the big differences of river discharge and because the samples were taken a week after the big flood in Jakarta area (February 4th - 6th, 2007). Total organic carbon fluxes from the river to the bay in February and May 2007 were 107.6 T /day C and 42.7 T /day C, respectively.Ã‚Â Key words : sediment, anthropogenic influence, C/N Ratio, POC, TOC, flux

KEMAMPUAN PENANGANAN TERHADAP ANCAMAN BENCANA TSUNAMI DI WILAYAH PESISIR KOTA CILEGON Diyah Krisna Yuliana; Iwan G. Tejakusuma
Jurnal Sains dan Teknologi Mitigasi Bencana Vol. 11 No. 1 (2016): Jurnal Sains dan Teknologi Mitigasi Bencana
Publisher : Badan Pengkajian dan Penerapan Teknologi (BPPT)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29122/jstmb.v11i1.3680

Wilayah pesisir Kota Cilegon merupakan daerah rawan gempa dan tsunami, karena posisinya yang berbatasan langsung dengan Selat Sunda yangÂ memiliki bahaya gempa dan dekat dengan Gunung Anak Krakatau. Pada tahunÂ 1883 pernah terjadi tsunami besar akibat letusan Gunung Krakatau yang telah memakan korban sekitar 36.000 jiwa. Risiko bencana tsunami akan sangat besar bagi Kota Cilegon karena terletak di wilayah pesisir dengan tingkat kepadatan penduduk dan aktivitas perekonomian yang cukup tinggi. Risiko bencana yang tinggi dapat diminimalisir jika suatu wilayah memiliki tingkat kemampuan penangananÂ atau kapasitas yang tinggi. Oleh karena itu kajian tentang kemampuan penanganan terhadap bencana tsunami di kota ini menjadi sangat penting. Penilaian kemampuan penanganan terhadap ancaman bencana tsunami ini dilakukan dengan menggunakan metode MCE (Multi Criteria Evaluation) dan teknik GIS (Geographical Information System). Kesehatan, kesiapsiagaan dan jumlah penduduk bekerja adalah tiga indikator penting yang digunakan dalam penilaian kemampuan penanganan di wilayah pesisir Kota Cilegon. Berdasarkan analisis MCE dan SIG diketahui bahwa Desa atau Kelurahan Randakari dan Kubangsari adalah desa atau kelurahan yang memiliki kemampuan penanganan terhadap bencana tsunami yang paling tinggi.

SOIL BIOENGINEERING DAN PERANANNYA DALAM GEOLOGI LINGKUNGAN Iwan G. Tejakusuma
Jurnal Sains dan Teknologi Mitigasi Bencana Vol. 11 No. 1 (2016): Jurnal Sains dan Teknologi Mitigasi Bencana
Publisher : Badan Pengkajian dan Penerapan Teknologi (BPPT)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29122/jstmb.v11i1.3684

Pengetahuan tentang geologi lingkungan memegang peranan yang sangat penting dalam setiap perencanaan pembangunan dan aktivitas manusiaÂ yang memanfaatkan lahan. Khususnya dalam pembangunan infrastruktur atauÂ keperluan lainnya maka pembukaan lahan dan pemotongan lereng tidak dapat dihindarkan. Akibatnya, bahaya yang mungkin terjadi diantaranya adalah erosi dan ketidakstabilan lereng. Untuk mencegah erosi dan ketidakstabilan lereng, salah satu upaya yang dilakukan adalah penerapan teknik soil bioengineering. Teknik ini menggunakan vegetasi untuk keperluan fungsi tersebut. Penerapan teknik ini memerlukan pemikiran yang serius dan hati hati terutama dalam hal fungsinya untuk meningkatkan kestabilan lereng.

BENCANA BANJIR BANDANG DI GARUT 20 SEPTEMBER 2016 Iwan G. Tejakusuma
Jurnal Sains dan Teknologi Mitigasi Bencana Vol. 11 No. 2 (2016): Jurnal Sains dan Teknologi Mitigasi Bencana
Publisher : Badan Pengkajian dan Penerapan Teknologi (BPPT)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29122/jstmb.v11i2.3686

Bencana banjir bandang terjadi di Garut pada 20 September 2016. Bencana ini merupakan bencana terbesar dalam sejarah kota ini dan menimbulkan korban jiwa sebanyak 33 orang tewas, 20 orang hilang tersapu aliran banjir bandang dan lebih dari 6300 orang mengungsi serta sekitar 2000 rumah mengalami kerusakan. Curah hujan yang sangat tinggi hingga mencapai di atas 150 mm atau tergolong ekstrim terjadi di hulu dan tengah Daerah Aliran Sungai Cimanuk. Perubahan penggunaan lahan dari hutan menjadi perkebunan menyebabkan run off menjadi semakin besar dan menyumbang faktor yang signifikan dalam terjadinya banjir bandang. Morfologi sungai berkelok pada setelah morfologi perbukitan dan pegunungan serta perkembangan permukiman di tepi sungai memberikan efek tingginya risiko bencana di Garut. Kombinasi curah hujan yang tinggi, perubahan penggunaan lahan dan morfologi sungai yang disertai dengan perkembangan permukiman di tepi sungai yang tidak ditata dengan baik menjadi faktor dominan untuk terjadinya bencana banjir bandang di Garut.

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