Tegangan geser pada aliran tidak seragam dalam saluran terbuka

ABSTRACT: In sediment transport problems, such as the initial motion of sediment particles, scouring process, sedimentation, etc., the information about the wall shear stress, ro is often needed. For uniform flow, the Clauser\u27s method, which is based on the velocity distribution data, is generally used to predict the wall shear stress, due to the simplicity and accurately of the method. However, for non-uniform flow, it might be still in question whether the Clauser\u27s method can be used or not. In this article, the validity of the Clauser\u27s method will be examined for non uniform flowin this case, the wall shear stress obtained from the clauser\u27s method will be compared with the one obtained from the Reynolds shear stress measurement data. The comparison of them shows a good agreement. This means that as long as the logarithmic velocity distribution is still valid in the near wall region, the Clauser\u27s method can be used to predict the wall shear stress of non-uniform flow

Kajian metode the empirical area reduction untuk prediksi distribusi endapan sediment pada beberapa waduk dengan karakteristik berbeda

Reservoir sedimentation as well as its sediment distribution during its time of reservoir operation is very related to its useful lifetime of reservoir. Reservoir sedimentation is a complicated subject, and techniques proposed to calculate sediment distribution are many and varied, and mainly empirical. Among of the existing methods found in the literature is the one proposed by Borland and Miller (1958), which is known as the empirical area-reduction method. The method has to take into account of the reservoir classification as one of four standard types as being proposed by the method. Sediment distribution data obtained from different reservoirs with different characteristics, i.e., reservoir with small, medium, and large capacity, as well as reservoir with short and long time of operation, are used as a base of comparison to the distribution calculated by the empirical method. The data are obtained from Mrica, Sermo, Wonogiri, and Selorejo reservoirs. From the investigation done here, it can be concluded that the empirical method proposed by Borland and Miller (1958) can be used to estimate sediment distribution of different characteristics of reservoirs, either for small, medium, and large reservoirs capacity. A problem is identified only for a small reservoir with short time of operation (as shown from Serino reservoir data). However, when the time of reservoir operation increases, the method can be used to predict sediment distributionthis is shown from Selorejo reservoir data. Key Words: Reservoir sedimentation - small dam

Sediment Delivery Ratio Pada Daerah Tangkapan Waduk Sermo

Sediment Delivery Ratio, SDR, is defined as the ratio of the quantity of sediment actually delivered out of the watershed (or deposit in a reservoir) to the total soil loss occurring initially at each source (calculated by the USLE formula). The smaller value of SDR means that the crop and land conservation managements are more effective. In this case, the SDR of the Sermo reservoir will be investigated in order to know whether its crop and land conservation managements are being effective or not. The investigation of the Sediment Delivery Ratio (SDR) of Sermo\u27s watershed will be done by calculating the soil erosion (using USLE formula) and compared with the sediment deposit in Sermo reservoir measured by echosounder. The Sediment Delivery Ratio (SDR) in Sermo\u27s watershed is obtained as 0,596it means that 59,6 % of soil erosion in the watershed enters and deposits in the reservoir. The remaining part of 40,4 % still deposits in the other part of the watershed With this SDR value of 0,596, the operation life of reservoir estimated to be shorter than planned Thus, the conservation management in the Sermo\u27s watershed shoud be improve

Pengaruh Angkutan Sedimen Dasar (Bed Load) terhadap Distribusi Kecepatan Gesek Arah Transversal pada Aliran Seragam Saluran Terbuka

In sediment transport problems, such as the initial motion of sediment particles, scouring process, degradation process, etc., the information about the wall shear velocity, u*, is often needed. How the wall shear velocity variates in transversal direction, as the function of slopes and discharges, either for flows with and without bed load transport will be studied. The wall shear velocities, u*, are evaluated using the Clauser\u27s method, which is based on the velocity distribution data, due to the simplicity and the accuracy of the method. Hundred and twenty five velocity distributions data with five different slopes and five different discharges are used to study the wall shear velocity in transversal direction. The results of analysis show that the Clauser\u27s method still remains valid, and can be used to determine the wall shear velocity in transversal direction, as long as the velocity distributions data n the near wall region still follow the logarithmic velocity distribution. Closer to the wall, the shear velocity becomes to decrease, which is not influenced by the existence of bed load transport, as well as by the variations of slopes and discharges variations

Distribusi Sedimen Suspensi Pada Aliran Seragam Dengan Dan Tanpa Angkutan Sedimen Dasar

Sediment transport in river, either suspended or bed load transport is very important and needed in river works. The Researchs done by many researchers showed that there is an interaction between bed load and suspended sediment, in which the increasing of bed load transport is usssualy followed by the increasing of suspended sediment. Based on this, the characteristics of suspended sediment on flow, both with and without bed load transport are studied here. The study was done by measuring flow velocity and suspended sediment concentration in laboratory, both for uniform flows either with bed load transport and without bed load transport, in the range of aspect ratio (b/D) 2.99 < b/D < 6.74. Elektromagnetic Currentmeter probe VMT-200 was used for flow velocity measurement and Foslirn probe-set 4M 110N was used for suspended sediment concentration measurement. The result shows that the velocity distribution on flow with bed load transport yields a more opened (fuller) than that without bed load transport. The constant Br value (in the logaritmic velocity distribution) on uniform flow without bed load transport is 8.5 ± 5 %, while for uniform flow with bed load transport, the Br-value tend to rise but still in the range of scattered given by the literature (8.5 ± 15 %). Distribution of suspended sediment for flow without bed load transport can be approached by using Rouse equation as well as by Tanaka & Sugimoto equation, while for flow with bed load transport, Tanaka & Sugimoto equation tends to have a better prediction than the Rouse equation. Distributions of turbulence intencity on flow with and without bed load transport show smaller value than Nezu & Rodi equation and Kironoto equation for clean water, in which the increasing of bed load transport, the turbulence intencity tends to decrease. Straub formula (1945) and Atmodjo & Kironoto formula (2001) developed for uniform flow without bed load transport can still be used on flow with bed load transport with the errors 5.1 % and 4.5 %, respectively. Keyword : velocity distribution, suspended sediment concentration, turbulence intencit

Aplikasi Model Matematika k-3 Untuk Prediksi Distribusi Sedimen Suspensi dalam Saluran Terbuka

Model matematika "k-s" yang dikembangkan untuk memprediksi struktur aliran turbulen dalam saluran terbuka, diterapkan untuk memprediksi distribusi dari konsentrasi sedimen suspensi. Model matematika "k-c" merupakan suatu model yang menyelesaikan secara numeris persamaan-persamaan pembentuk dari aliran (yaitu, persamaan momentum, kontinuitas dan persamaan transpor), dengan bantuan suatu persamaan pendukung, yaitu yang menyatakan hubungan antara energi kinetik turbulen (turbulent kinetic energy), k, dengan energi disipasi (rate of dissipation),s. Dengan menggunakan model matematika "k-c", dan input data berupa data debit aliran per satuan lebar, kedalaman, kemiringan, dan kekasaran dasar saluran, struktur aliran turbulen seperti misalnya distribusi kecepatan, viscositas turbulen (eddy viscosity), dan tegangan geser Reynolds (Reynolds shear stress) dapat diperoleh. Dengan menganggap bahwa turbulent diffusivity proporsional dengan eddy viscosity, distribusi dari sedimen suspensi dapat ditentulcan. Perbandingan antara data pengukuran laboratorium dengan hasil hitungan dari model matematika "k-c" cukup memuaska

KAJIAN PERUBAHAN EROSI PERMUKAAN AKIBAT PEMBANGUNAN HUTAN TANAMAN INDUSTRI DI AREAL PENCADANGAN HTI KABUPATEN KETAPANG PROPINSI KALIMANTAN BARAT

Allocated area for planted-forest in Ketapang Regency, especially in Durian Sebatang river basin and its surrounding are in critical condition with low land- productivity and poor hydrologic characteristic. These areas have to be conserved with vegetative method. One of the efforts to synergize soil and water conservation and economic interest is immediately to rehabiliiate the critical areas with Planted-Forest (Hutan Tanaman Industri-HTI). Planted-forest system can be arranged to control the rate of erosion. The aim of this study is to predict the rate of erosion at the existing condition and the change of erosion rate at the planting-rotation system (cutting system) in the planted-forest of Acacia sp. The planting- rotations are 5 years, 6 years, 7 years and 8 years during the range of 11 years study. The research uses the version 3.3 of GIS Arc View program to make the land-unit map. The amount of surface erosion (sheet erosion) estimated base on the land-unit map. The calculation of the erosion rate uses the Modified USLE method (Snyder, 1989), in which factors influencing the amount of surface erosion are Rain\u27 Erosivity (R), Land Erodibility (K), Length and Elevation of slope (LS) and Soil Conservation Factor and Planting System (VM). The results of the study show that the rate of erosion at the existing condition {s 1,24 mm/year. Its a light danger erosion level, under the soil loss tolerance limits (2 mm/year). During the 11 first years of HTI development, the rate of erosion in planted forest with planting rftation of 5, 6, 7 and 8 years ranges from 0,91 mm/year to 2,66 mm/year. Its included in a very light to heavy erosion danger level. The lowest average erosion rate is found in the planting rotation of 7 year, continued by 8, 6 and 5 year. At first cycle, the rates of erosion in all planting rotation are more than the amount of existing erosion. Its caused by land clearing activity for plantation, but at further cycle, those are decrease until under the existing condition when the vegetation at conservation areas reach to an optimal growth. The rates of erosion in HTI can be controlled ifwe arrange the allocation of land utilization t consider by soil type. The reasonable planting~rotation of HTI with Acacia sp vegetation\u27s type to be applied in the research area is 6 years or 7 years. The optimal planting rotation is decided base on amount of erosion rate, soil stability, wood utilization and economic value. The expectation of this research can be contribute in soil conservation and social economic integrated development program

Studi Penanganan Bencana Gempa di Bantul 27 Mei 2006

On May 27 th , 2006 at 05:53, 57, a 5,9 Richter scale earthquake occurred. Bantul Regency in Yogyakarta Province was the most severe area. However, existing institutions had limited capability to perform a proper disaster management they also failed to generate the community to participate, especially during the emergency respose period. Therefore, it is required to have an integrated policy for disaster management to meet related parties expectations and to conduct more optimum disaster management. The objective of this study is to obtain best alternatives in handling disaster using the Decission Support System (DSS) eith Analytical Hierarchy Process (AHP) as the method. Three alternatives were analized formatting special office for disaster management (Alternative 1), formatting community based disaster management (Alternative 2), and ascociating the disaster management between interrelated agencies and the local government as the control center (Alternative 3). These alternative were selected based on fuor criterias management, financial, capacity and policy aspect. This study was taken during, the emergency response period performed by SATLAK PBP Bantul. Input for the analysis was questionnaire result given to 120 respondents composing af 30 respondents from bureaucratic element (SATLAK and SATKORLAK PBP members) and 90 respondents from nine villages in three districts. Numeric values were given to each element of the questionnaire result (criterion, sub criterion and alternative). Then, the values were compared to the established comparison scale obtain the lever of interest. Result of this study showed that each criterion of financial, management policy and capacity aspects weighted 0,273, 0,265, and 0,208 respectively. The best alternative of optimum disaster management was alternative 2. The second anf the third were alternative 1 and alternative 3. The community based organizations objective was to improve the people participation in pertaining, preventive, counter measuring and self healing by actively involve in the planning and executing process of disaster management

Bed-Shear Velocity Measurement in Curved Open Channel

Generally, the condition of the rivers in Indonesia are alluvial rivers which had meanders, where the change in the river bed topography often occur. One of the parameters associated with changes in the river bed topography is bed-shear velocity, or Reynolds stress. The bed-shear velocity can be calculated by the Reynolds stress distribution method and the Clauser method which commonly used in straight channels. In fact, on natural channel there is a curve and even a meandering channel. With more complex flow conditions, the use of the Clauser method in curved channels can be questioned, is it still accurate or not. In this paper, both methods will be discussed by comparing the measurement data in the laboratory using 180° curved channel with flat bed. The results of data analysis show that the use of these two methods in curved channels produces an average difference of around 19.81%, where the Clauser method gives greater results and better tendencies. Apart from the differences in the results given, it can be said that the Clauser method as well as the Reynolds stress distribution method can still be used to calculate the bed-shear velocity in the curved channel.

Hydrology and Hydraulic Analysis of Nasiri Flash Flood Disaster Event on the 1st August 2012

Nasiri lays in the Luhu village, Huamual district, West Seram Regency, Maluku province. Nasiri experienced in flash flood on August 1st, 2012 which had never happened before. There was no rainfall station and water level recorder at that time. It is rather difficult to find out the cause and yet Nasiri River was only 8 meters wide. The research started with identifying base flow, soil characteristics, learning flood video record, routing the river reach, finding the nearest rainfall station, and also interviewing some peoples there. Field data area was complemented with satellite radars. AutoCAD 2007, IFAS 2.0.1.2, Geostudio 2004, ArcGIS 10.2, HEC-HMS 4.2.1, and HEC-RAS 5.0.3 were used to perform simulations of the natural river with and without precipitation calibration, and also with and without landslide dam in the river. HEC-RAS was subject to perform 2 (two) dimensional flood routing. The result was fairly satisfying. Nasiri watershed was experiencing in flash flood caused by 2 (two) landslide dams which collapsed in 2 (two) different times. The first landslide dam was 7.55 meters high which collapsed at 09:52 (UTC+9) with 83.58 m3/s of peak discharge. The second landslide dam was 8.91 meters high which collapsed at 14:24 (UTC+9) with 54.16 m3/s of peak discharg