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All Journal BULLETIN OF THE MARINE GEOLOGY Jurnal Geologi Kelautan: Media Hasil Penelitian Geologi Kelautan Jurnal Riset dan Pengabdian Interdisipliner
Purnomo Raharjo, Purnomo
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Humanities Earth & Planetary Sciences Education Environmental Science Social Sciences Other

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DINAMIKA PANTAI KOTA SEMARANG, JAWA TENGAH Raharjo, Purnomo; Prasetio, Fauzi Budi; Hawari, G.N.; Kristanto, Nur Adi
JURNAL GEOLOGI KELAUTAN Vol 22, No 2 (2024)
Publisher : Pusat Penelitian dan Pengembangan Geologi Kelautan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/jgk.22.2.2024.926

Abstract

Wilayah pesisir Kota Semarang, bagian dari pantai utara Jawa, menghadapi dinamika pantai yang kompleks akibat abrasi, akresi, banjir pesisir, dan perubahan garis pantai yang signifikan dalam dua dekade terakhir. Permasalahan ini diperburuk oleh intensitas pembangunan yang tidak mempertimbangkan kondisi geomorfologi, topografi, dan sistem drainase, yang mengakibatkan kerentanan terhadap abrasi dan sedimentasi tidak merata. Penelitian ini bertujuan untuk mengevaluasi perubahan garis pantai, memahami pengaruh faktor oseanografi dan antropogenik terhadap dinamika pantai, serta memberikan dasar untuk perencanaan pengelolaan pesisir yang berkelanjutan. Penelitian menggunakan metode integrasi Sistem Informasi Geografis (SIG) dengan Digital Shoreline Analysis System (DSAS) untuk memetakan perubahan garis pantai berdasarkan data multi-temporal dari citra satelit selama 20 tahun. Selain itu, dilakukan analisis energi fluks gelombang melalui metode hindcasting menggunakan data angin selama 10 tahun dari National Centers for Environmental Information (NCEI) NOAA. Data angin dianalisis menggunakan koreksi elevasi, stabilitas, durasi, lokasi pengamatan, serta klasifikasi berdasarkan arah dan kecepatan menggunakan Beaufort Scale. Selanjutnya, energi fluks gelombang dihitung untuk mengidentifikasi pola distribusi sedimen dan pengaruhnya terhadap proses abrasi dan akresi. Verifikasi lapangan dilakukan melalui survei langsung untuk mengamati karakteristik pantai, termasuk jenis sedimen, morfologi pantai, dan pola vegetasi di berbagai lokasi strategis. Hasil penelitian menunjukkan bahwa Kecamatan Genuk mengalami abrasi paling luas, sedangkan akresi terbesar terjadi di Kecamatan Semarang Barat. Faktor oseanografi seperti arus sejajar pantai (longshore current), gelombang, serta reklamasi yang dilakukan di beberapa titik turut memengaruhi distribusi sedimen. Analisis energi fluks gelombang mengungkapkan pola transportasi sedimen yang dominan dari timur ke barat, menyebabkan perubahan geomorfologi pantai yang dinamis. Hasil penelitian ini menegaskan bahwa pemanfaatan SIG dan DSAS memberikan gambaran komprehensif tentang dinamika pantai, yang dilengkapi dengan hasil analisis energi fluks untuk memahami transportasi sedimen. Studi ini merekomendasikan penerapan kebijakan mitigasi berbasis data untuk mengurangi dampak abrasi, memaksimalkan manfaat akresi, dan meningkatkan ketahanan pesisir Kota Semarang terhadap perubahan iklim dan aktivitas manusia. 
BEARING CAPACITY AND SETTLEMENT BEHAVIOUR OF COASTAL SOIL FOR THE PLANNED BALONGAN PORT DEVELOPMENT, WEST JAVA Ekasara, Adam Raka; Raharjo, Purnomo; Susilowati, Susilowati
BULLETIN OF THE MARINE GEOLOGY Vol 40, No 1 (2025)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.40.1.2025.943

Abstract

The planned development of Balongan Port in West Java requires a comprehensive geotechnical evaluation to support foundation planning at the proposed site, which is underlain by soft, clay-rich sediments. This study aims to assess the bearing capacity of the subsurface and predict potential settlement behaviour by integrating field and laboratory investigations. Standard Penetration Test (SPT) data from two boreholes, BH-3 (14 m) and BH-4 (18 m), and were complemented by laboratory analyses of soil physical and mechanical properties. The site is primarily composed of high-plasticity clay, known for its low strength, high compressibility, and variable geotechnical characteristics. Calculations based on SPT results yielded allowable loads of 53.1 tons at BH-3 and 39.0 tons at BH-4, respectively, while laboratory analyses indicated significantly higher bearing capacities of 265.9 tons and 884.4 tons, respectively. Settlement predictions based on SPT and laboratory data were 0.61 cm and 2.07 cm, with an estimated 90% consolidation period of about 12.9 years. These findings emphasize the variability and compressibility of the soft clay strata as well as the importance of employing multiple assessment methods. The study provides essential input for foundation planning and highlights the need for integrated geotechnical assessment methods to ensure the safety, reliability, and long-term performance of pile-supported structures at the proposed port site.
Geomorfologi Daerah Bajo dan Sekitarnya, Kecamatan Tilamuta, Kabupaten Gorontalo Hemu, Alit Anastasya; Arifin, Yayu Indriati; Raharjo, Purnomo
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Publisher : Universitas Negeri Gorontalo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37905/jrpi.v2i4.35076

Abstract

This study aims to analyze the geomorphological conditions of Bajo Village and its surroundings, Tilamuta District, Boalemo Regency. The methods used include slope analysis, river flow patterns, and geomorphological units. The data employed consist of topographic maps, satellite images, and the National Digital Elevation Model (DEMNAS), processed using ArcGIS software. Slope analysis was conducted to determine the steepness of the land, while river flow patterns were classified according to Howard (1967). Determination of geomorphological units was carried out through the interpretation of morphology and lithology, referring to Van Zuidam (1983). The results show four geomorphological units, namely fluvial lowlands, marine lowlands, low structural hills, and inland volcanic lowlands. The study area has slopes ranging from flat to steep, with rectangular river flow patterns dominant in the northeastern part. Overall, the geomorphological conditions of this area are influenced by lithology, geological structures, and fluvial processes that actively shape the local morphology.
Geomorfologi Daerah Bolihutuo dan Sekitarnya, Kecamatan Botumoito, Provinsi Gorontalo Paendre, Asdini; Arifin, Yayu Indriati; Raharjo, Purnomo
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Publisher : Universitas Negeri Gorontalo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37905/jrpi.v2i4.35074

Abstract

The Bolihutuo area and its surroundings, in the Botumoito District, have geomorphological characteristics that are interesting for research, as they feature complex geomorphological conditions influenced by volcanic activity, fluvial processes, and structural factors. This study aims to map and classify the geomorphological units in the research area. The methods applied include spatial analysis and field observation. The results of this study indicate that the area has four main geomorphological units: structural hill units, volcanic hill units, fluvial plain units, and marine plain units. The morphography of the research area consists of lowlands and low hills with elevations ranging from 0 to 187.5 meters above sea level. Slope gradients vary from flat to very steep, while the river flow patterns are sub-parallel with young and mature river stages.The lithology consists of gabbro, andesite, granodiorite, granite, dacite, and alluvial deposits, and the land can be utilized for settlements, agriculture, and infrastructure development, adjusted according to its slope.
Co-Authors Ekasara, Adam Raka Fauzi Budi Prasetio Hawari, G.N. Hemu, Alit Anastasya Kristanto, Nur Adi Paendre, Asdini Susilowati Susilowati Yayu Indriati Arifin