Djoko Legono
Fakultas Teknik, .lurusan Teknik Sipil Universitns Gadjah Mada, Yogyakarta

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Sediment Bypass Modelling of Volcanic Rivers (A Case Study: Boyong River, Merapi Mount, Indonesia)

MEDIA KOMUNIKASI TEKNIK SIPIL Volume 14, Nomor 2, Edisi XXXV, JUNI 2006
Publisher : Department of Civil Engineering, Diponegoro University

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Abstract

Sedimen yang diangkut oleh sungai-sungai yang berasal dari gunung berapi sering mempunyai jumlah yang sangat banyak sehingga dapat mengundang permasalahan berupa daya rusak yang ditimbulkan ataupun bahkan dampak negatif lainnya. Penanggulangan yang telah ditempuh selama ini adalah dengan cara membangun bangunan pengendali sediment atau bangunan sabo yang ditujukan untuk mengurangi besarnya daya perusak tersebut dengan cara menahan laju aliran sediment yang mengalir ke hilir. Dalam hal suplai sedimen dari gunung berapi tersebut relative besar maka kehadiran bangunan sabo terlihat nyata manfaatnya. Namun pada saat dimana suplai sedimen berkurang, maka kehadiran bangunan sabo sering dinilai sebagai penyebab utama terjadinya degradasai dasar sungai di ruas-ruas sungai sebelah hilir bangunan sabo. Paper ini membahas hasil studi tentang efektivitas suatu bangunan pengalihan sedimen (sediment bypass), dalam rangka mengurangi besarnya suplai sedimen yang masuk pada suatu sungai,  yang kemudian dialihkan pada sungai yang lain. Studi dilakukan dengan mengambil kasus Kali Boyong dan Kali Kuning yang berhulu di puncak Gunung Merapi, Daerah Istimewa Yogyakarta. Teori pendekatan imbangan sedimen diaplikasikan pada suatu geometri bangunan pengalihan, yang selanjutnya diperbandingkan dengan hasil pengujian model fisik. Hasil studi menunjukkan bahwa aplikasi persamaan imbangan air (konservasi massa) pada bangunan pengalihan sedimen mempunyai nilai yang mendekati dengan hasil yang diperoleh dari pengujian model fisik. Hasil studi dapat digunakan untuk menentukan geometri yang sesuai dengan rencana penetapan jumlah pengalihan sedimen dari Kali Boyong ke Kali Kuning.Kata kunci: bangunan pengalihan sedimen, daya perusak, imbangan sedimenPermalink: http://www.ejournal.undip.ac.id/index.php/mkts/article/view/3941[How to cite: Legono, D., 2006, Sediment Bypass Modelling of Volcanic Rivers (A Case Study: Boyong River, Merapi Mount, Indonesia), Jurnal Media Komunikasi Teknik Sipil, Volume 14, Nomor 2, pp. 142-149]

Dividing Streamline Formation Channel Confluences by Physical Modeling

IPTEK The Journal for Technology and Science Vol 21, No 1 (2010)
Publisher : Institut Teknologi Sepuluh Nopember

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Abstract

Confluence channels are often found in open channel network system and is the most important element. The incoming flow from the branch channel to the main cause various forms and cause vortex flow. Phenomenon can cause erosion of the side wall of the channel, the bed channel scour and sedimentation in the downstream confluence channel. To control these problems needed research into the current width of the branch channel. The incoming flow from the branch channel to the main channel flow bounded by a line distributors (dividing streamline). In this paper, the wide dividing streamline observed in the laboratory using a physical model of two open channels, a square that formed an angle of 30º. Observations were made with a variety of flow coming from each channel. The results obtained in the laboratory observation that the width of dividing streamline flow is influenced by the discharge ratio between the channel branch with the main channel. While the results of a comparison with previous studies showing that the observation in the laboratory is smaller than the results of previous research.

KAJIAN PENGELOLAAN AIR IRIGASI BENDUNG PIJENAN

Civil Engineering Forum Teknik Sipil Vol 17, No 2 (2007): MEI 2007
Publisher : Civil Engineering Forum Teknik Sipil

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Abstract

Bantul Regency is about 506.85 km2 consists of 16,440 ha paddy fields and 34,245 ha upland fields. The Pijenan weir is one of weirs located in Bedog river in Bantul Regency. The weir provides irrigation water for Jigutan command area (Pijenan Upstream) of 2.074 ha. Kebonongan command area was previously irrigated from Kamijoro free intake in Progo River. The Kamijoro free intake did not properly function properly due to the sediment deposited in 1969. This condition requires supply taken from Pijenan weir. Irrigation water supply taken to Kebonangan command area can be carried out if irrigation water to Jigutan command area has been optimum. Optimally utilized irrigation water for Jigutan command area is necessary based on the crop pattern and crop variety in order to maximize the farmers’ profit. Based on the restitution of irrigation management policy, farmers free to decide which crop variety will be cultivated in accordance to paddy-paddy-palawija pattern. Paddy as the main crop and palawija (corns, beans, peanuts, onion, and chilly) can be cultivated anytime in order to gain the maximum profit based on the available water in Jigutan command area. The optimization analysis of irrigation water allocation for Jigutan command area was performed using the linear program. Water allocation for Jigutan command area of 100% and 50% of available water resulted in optimum cultivation area of 822.88 ha with profit of Rp 7.688.517.507,00 and 612.88 ha with profit of Rp 6.743.877.335,00. The crop intensity with water allocation of 100% and 50% was 278% (197% paddy and 81% palawija) and 207.05% (114.05 paddy and 93% palawija), respectively. These results described that the optimum area of paddy crop cultivation is significantly sensitive to irrigation water allocation compared to the palawija market price. This explains why the profit obtained by the farmers is dependent from the palawija variety. Results of the optimization of irrigation water allocation of 100% and 50% of the available water to Jigutan command area provides annual supply to Kebonongan command area for 155.233.586 m3 and 75.316.444 m3, respectively.

KAJIAN PENANGANAN BANJIR KALI CILIWUNG DKI JAKARTA DITINJAU DARI ASPEK HIDRO-EKONOMI (STUDI KASUS PADA RUAS CAWANG – PINTU AIR MANGGARAI)

Civil Engineering Forum Teknik Sipil Vol 17, No 3 (2007): SEPTEMBER 2007
Publisher : Civil Engineering Forum Teknik Sipil

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Abstract

Every year in a rainy season, flood inundates several areas along Ciliwung River, especially in the Cawang – Manggarai reach. Flood in this reach is caused by land use changing in upstream area and narrower the river width in the downstream area. Several planning will be implemented to reduce the flood, which are normalization with widening river, revetment and dike construction also diversion channel from Ciliwung River to East Banjir Kanal. To determine the benefit of every flood control structure the integrated and comprehensive considerations is required. The study of performance of flood management planning with hydro-economy approach that considers hydrologic, hydraulic and economic aspect is conducted in this study. The aim of this study is to determine the benefit of every flood control structure. Before determining the benefit of flood control structure, the expected annual damage must be calculated, the calculation is based on discharge-probability of exceedence curve, discharge-stage curve and stage-damage curve. The relation from above three curves will be needed for damage-probability of exceedence curve. As a result from this curve the expected annual damage and the benefit of flood control structure can be determined. The results of analysis are that the benefit of flood control structure for normalization, diversion channel with 2,5 m in width gate, diversion channel with 3,0 m in width gate and diversion channel with 3,5 m in width gate are Rp. 20 billion, Rp. 16.1 billion, Rp. 18.9 billion and Rp. 20.1 billion respectively.

PENGELOLAAN SEDIMEN KALI GENDOL PASCA ERUPSI MERAPI JUNI 2006

Civil Engineering Forum Teknik Sipil Vol 18, No 2 (2008): MEI 2008
Publisher : Civil Engineering Forum Teknik Sipil

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Abstract

The Gendol River, with its catchment area of 66 km2 and the river length of about 22 km, originates from the south east of Mount Merapi. Nineteen sabo dams have been built in order to anticipate and control sediment disaster. The most upstream dam is Kaliadem (+1.100 msl) and the most downstream dam is consolidation dam of GE-C0 (+163 msl). Sand mining occurs at several points along the river and cause environmental damage. In order to conserve environment and to maintain sediment balance a proper sediment management is required. The research is conducted based on sediment balance. The analysis of transportable sediment volume (VS) is conducted using empirical formula of Takahashi (1991) and Mizuyama (1977). Over flow sediment volume (VE) was analyzed using empirical equation of Shimoda (1995). Sediment balance was analyzed based on maximum daily rainfall (R24) with 25 years return period. The result of the study shows that the sabo system in Gendol River effectively works to control lahar flow. As a conclusion, the existing sabo dams are able to maintain sediment balance in Gendol River. The possible amount of sand mining is estimated about 1.253.422 m3 and the allowable daily sand mining volume is estimated about 836 m3 per day.

MITIGASI BENCANA ALIRAN DEBRIS SUNGAI BELANTING SECARA NON STRUKTURAL DESA BELANTING KECAMATAN SAMBELIA KABUPATEN LOMBOK TIMUR – NUSA TENGGARA BARAT

Civil Engineering Forum Teknik Sipil Vol 18, No 3 (2008): SEPTEMBER 2008
Publisher : Civil Engineering Forum Teknik Sipil

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Abstract

Belanting village, situated in the foot of Rinjani mountain range and crossed over by Belanting River, is a fast-growing village. Almost all of its inhabitants are migrants who came there on their own support. On January 21, 2006, a disaster strucked: debris flow came, taking people’s lives and creating havoc to local infrastructures. One of the difficulties in the area is that the lack of non-structural disaster mitigation. At this rate, a study is required concerning the awareness of local inhabitants of the threat posed by debris flow hazard. The objective of the study is to identify the level of local people’s understanding on debris flow disaster, to be functioned as determining basis for disaster management pattern by non-structural mitigation. Data were collected from questionnaires and interviews for 80 respondents. The resulting questionnaire data were then analyzed using SPSS (Statistic Pocket for Social Science). Result of the analysis indicates that 52.5 per cent of respondents have not understood the threat of disaster. In the meantime, the interviews indicate that religious leaders (Tuan Guru) hold high social status. Based on the result of the analysis and interviews, there is a need for a strategy in non-structural mitigation program and, as far as the study is concerned, socialization during public religious learning regarded as more effective and efficient efforts.

Reservoir Operation to Minimize Sedimentation

International Journal of Science and Engineering Vol 6, No 1 (2014)
Publisher : Chemical Engineering Diponegoro University

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Abstract

The Wonogiri Reservoir capacity decreases rapidly, caused by serious sedimentation problems. In 2007, JICA was proposed a sediment storage reservoir with a new spillway for the purpose of sediment flushing / sluicing from The Keduang River. Due to the change of reservoir storage and change of reservoir system, it requires a sustainable reservoir operation technique. This technique is aimed to minimize the deviation between the input and output of sediments. The main objective of this study is to explore the optimal Wonogiri reservoir operation by minimizing the sediment trap. The CSUDP incremental dynamic programming procedure is used for the model optimization.  This new operating rules will also simulate a five years operation period, to show the effect of the implemented techniques. The result of the study are the newly developed reservoir operation system has many advantages when compared to the actual operation system and the disadvantage of this developed system is that the use is mainly designed for a wet hydrologic year, since its performance for the water supply is lower than the actual reservoir operations.Doi: 10.12777/ijse.6.1.16-23 [How to cite this article:  Wulandari, D.A., Legono, D., and Darsono, S., 2014. Reservoir Operation to Minimize Sedimentation. International Journal of Science and Engineering, 5(2),61-65. Doi: 10.12777/ijse.6.1.16-23]

Laboratory Study on Comparison of the Scour Depth and Scour Length of Groundsill with the Opening and Groundsill without the Opening

Journal of the Civil Engineering Forum Vol. 2 No. 1 (January 2016)
Publisher : Department of Civil and Environmental Engineering, Faculty of Engineering, UGM

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Abstract

River bed control structure what so called groundsill or bottom sill is built for controlling a river bed to remain stable against degradation. Unlike other river obstacles, the presence of groundsill might cause sediment retention upstream of the structure; hence it reduces the supply of sediment to the downstream part of the river. At some extent, the above situation might create unexpected negative impact, not only cease the sediment migration but also disable fish migration, as well as the utilization of river for navigation. This paper presents the hydraulic investigation on various models of groundsill, i.e. groundsill without the opening and groundsill with a certain type of the opening. Series of laboratory experiments were conducted on an open channel flow of 0.75m width and longitudinal slope of 0.05%. There were two types of groundsill, i.e. groundsill without the opening with 0.75m width and 0.05m height, and groundsill with the opening of 0.39m width and 0.005m height of crest at the opening and 0.05m at the wings. Various flow rates were then introduced, necessary data were taken, and the hydraulic phenomena were studied. The results showed that groundsill without the opening produced non-dimensional (relative to the channel width) scour depth of 0.036, and scour length of 0.253. Groundsill with the opening produced scour depth of 0.013 and 0.024 near the downstream end of the wing section and the opening respectively. The scour length of the groundsill with the opening is 0.080 and 0.293 near the downstream end of the wing section and the opening section respectively. Moreover, it can be noted that the presence of the scour depth and scour length of the groundsill with the opening was generally much smaller rather than that of groundsill without the opening. The above results give the evidence that groundsill with the opening is much friendlier and also more suitable for the environment needs.Keywords: control structure, environmentally sound, groundsill, hydraulic phenomenon

Penerapan Optimasi Parameter pada Metode Exponential Smoothing untuk Perkiraan Debit

MEDIA KOMUNIKASI TEKNIK SIPIL Tahun 18, Nomor 1, PEBRUARI 2010
Publisher : Department of Civil Engineering, Diponegoro University

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Abstract

Exponetial smoothing is a technique that is very easy to apply and very effective as forecasting tool. However it requires the estimation of a parameter in order to get good acceptable result. The paper present the optimization is performed by using LINGO 11. The Resulted parameter gives predicted values closestto the observed data, and produces very good prediction as indicated in the MAE and MSE values better than other methods. Keywords : Discharge prediction, Parameter optimization, Exponential smoothing   Abstrak   Exponential smoothing adalah suatu metode yang sangat mudah untuk diterapkan dan sangat efektif dalam peramalan. Akan tetapi, penerapan metode Exponential smoothing ini memerlukan perkiraan parameter smoothing yang tepat. Dalam paper ini disajikan teknik optimasi parameter untuk memperkirakan parameter smoothing yang menghasilkan error yang minimum. Dalam optimasi yang digunakan LINGO 11. Parameter yang dihasilkan memberikan hasil prediksi yang paling dekat dengan data observasi , serta memberikan hasil yang lebih baik sebagaimana ditunjukkan dengan nilai MAE dan MSE dibanding dengan metode lain. Kata-kata Kunci : Perkiraan debit, Optimasi parameter, Exponential smoothing

ANALISIS PERAN SERTA MASYARAKAT DALAM PENGELOLAAN AIR BERSIH

Jurnal Manusia dan Lingkungan (Journal of People and Environment) Vol 11, No 2 (2004)
Publisher : Pusat Studi Lingkungan Hidup Universitas Gadjah Mada

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Abstract

Kondisi air sungai yang terpolusi karena penebangan hutan, penambangan, dan limbah domestik menyebabkan rendahnya kualitas air yang dikonsumsi masyarakat. Pada tahun l996 telah dibentuk Unit Pengelola Air (UPS-AB) oleh komunitas di Kumpai Batu untuk membantu pengadaan air bagi masyarakat. Studi ini dilakukan untuk mengkaji kinerja UPS-AB melalui survai lapangan terhadap 160 rumah tangga. Variabel yang dikaji meliputi aktivitas UPS-AB. cara pengelolaannya dan keterlibatan masyarakat dalam pengelolaan air. Data ini kemudian diproses dengan analisa deskriptif dan analisis regresi. Hasil analisis menunjukkan bahwa tingkat partisipasi masyarakat cukup tinggi. Tingginya tingkat partisipasi ini disebabkan karena kebutuhan komunitas yang tinggi akan pelayanan air. Meskipun demikian masyarakat merasakan pentingnya peningkatan pengelolaaut air oleh UPS-AB khususnya dalam hal: peningkatan kualitas air. kontinuitas suplai. sistim pembayaran dan sistim pencatatan.