Ocean Science and Coastal Engineering

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Authors: I. Gusti Bagus Sila Dharma, Windy Candrayana
Abstract: Benoa Bay is a micro tidal semi-enclosed water with a size of 10 km x 15 km of the inner bay with a narrow gap formed by Serangan Island and Benoa Peninsula. Benoa Bay is a strategic area in south of Bali Province linked to the Indian Ocean through a narrow entrance. Recently, a large amount of siltation occurred in this area, which is caused by sedimentation from five rivers discharged into the bay. The sedimentation in the lagoon is of ecological and physical concern due to the mangrove ecosystem disturbing and operation of Benoa port for the necessity of increased dredging. This paper deals with tide-induced flows in a semi-enclosed water body in a micro-tidal environment that is subjected to tide and river discharge conditions. In this study, The Coastal Modeling System (CMS) developed by Coastal Inlets Research Program was used for simulating flow, waves, sediment transport, and morphology changes in coastal areas. This CMS has effectively calibrate the data set supplemented by field observations.
Authors: Aditya Pamungkas, Ivonne M. Radjawane, Hadikusumah
Abstract: Raja Ampat Sea has a complex geometry and passed by Indonesian Throughflow (ITF) causing a very dynamic water condition, that condition also amplified by turbulent mixing. To gain better understanding of process and extent of turbulent mixing in Raja Ampat Sea, this research calculate Brunt-Vaisala frequency, Richardson number, turbulent kinetic energy dissipation rate and vertical diffusivity coefficient. The data obtained from Expedition Widya Nusantara (EWIN) by P2O-LIPI in the territorial of Raja Ampat Sea on 14-24 November 2007, by using 12 out of 33 observation stations. From this research, it is known that in 0-40 m (mixed layer) and 250-400 m (deep layer) have Richardson number (Ri) less than 0.25 and high vertical diffusivity coefficient (Kv), It proves a strong turbulent mixing occurs at those depth. Furthermore, Raja Ampat Sea has strong turbulent mixing with average value of turbulent kinetic energy is 2.64 WKg-1and vertical diffusivity coefficient is 1.65x10-3 m2s.
Authors: Suntoyo, Made Mustika Wijaya, Silvianita, Hasan Ikhwani
Abstract: Investigation of sediment transport rate induced by tidal current and wave-current interaction are very important to explain the sediment transport mechanics, sedimentation and erosion process, and also the coastal morphological changes. The understanding of sediment transport caused by wave and current interaction in detail should be known well in order to predict it, accurately. This paper aim to investigate the characteristics of sediment transport rate due to tidal current and wave-currents interaction motion in the the channel water intake by using numerical modelling. The performance of the modelling results indicated by the Root Mean Square (RMSE) with error of 0.5 % by means validating the model water surface elevation from the fields measurement data and the modelling results. The result showed that sediment transport caused by wave-current interaction give more the amount of total sediment transport than caused by tidal current only. It can be concluded that the wave has dominant effect than tidal current to conduct sedimentation and morphological change in the canal water intake.
Authors: Novi Andhi Setyo Purwono, Nizam, Radianta Triatmadja
Abstract: The tsunami waves when reached the coast has a potentially damage and large destroye, which has a velocity of 150-500 km/h and when arriving at the coast will sweep all existing buildings around the coast. The current research on tsunami wave has been done, but in general against buildings or scour. Research on the use of vegetation as an energy absorbers tsunami waves is still lacking. Pacitan coast is one of the coasts that are used to simulate the use of vegetation as a greenbelt in reducing tsunami wave. In observation of Casuarina Equisetifolia plants as greenbelt, plant age, density, planting pattern, stem diameter and the diameter of the limb into the goal in measuring. The measurement results will be used as the initial in the research use of greenbelt plants against tsunami waves. These measurements will continue to be done in intervals of 1 year to see the development of the plant. The measurement results of this investigation will serve as a field data input greenbelt plant modeling laboratory in order to obtain theoretical approach regarding the use of plants in reducing tsunami.
Authors: Aries Dwi Siswanto, Wahyu Andy Nugraha, Ashari Wicaksono
Abstract: Coastal dynamics and stability becomes the distinctive characteristics in northern coastal at Bangkalan. Coastal morphology are dominated by beach sloping, substrate, and hydrooceanographics factors. One of the indicators was suspended sediment fluctuations. This study aims to know the shoreline changes use indicator suspended sediment and image overlay analysis. The research was conducted in April 2015 in the northern and western coastal region of Bangkalan. The main material in this study was suspended sediment samples and the substrates were taken at 28 points, and the image data of Landsat TM 1994 and 2014. Analysis of sediment suspension is using gravimetric method and substrate analysis using ASTM method. Data analyzed at the Laboratory of Marine Science, Trunojoyo University. The result shows in the northern and western coast at Bangkalan regency is dominated by sand and mud as well as a mixture both of them, the coastal waters are dynamic. The distribution of suspended sediment are relatively diverse in all locations with a range of 25-190 mg/L and can be used as an early indication of shoreline changes as a result of erosion and sedimentation. Landsat TM image analysis using 1994-2014 showed almost all areas in the northern and western coastal at Bangkalan regency are both abrasion and sedimentation.
Authors: Marita Ika Joesidawati, Suntoyo
Abstract: Changes in the shoreline setback is a major threat of coastal areas dominated by sandy beaches and coastal lowlands. The impacts of sea level rise itself will be greatly felt by coastal regions in the island nations, such as Indonesia. Tuban is one of northern coastal areas in East Java, which includes the areas where the condition of beaches damaged. Thus, it is necessary to investigate the characteristics of beaches in Tuban, and how much the sea level rise occurs in Tuban district as well as the extent of its influence on the shorelines of Tuban. The calculation of sea level rise was predicted using the Least Square Method with tidal data of Semarang city in 1985-2014 which was later adopted as the tidal of Tuban, and the sea level rise at the beaches in Tuban, which was estimated at 0,024 meter annually by implementing the equation of y = 0.002x + 0.751. In the year of 2050 and 2100, the rise of the sea level reaches 2.55 m and 3.54 m respectively. The most appropriate method used is the Hennecke method, with the error value of 0.27%. The error value of Hennecke method is smaller than the error value of Bruun Rule method, which reaches 0.38%. Using Hennecke method, the prediction of the shoreline changes in Tuban with the starting point of the year of 2008 shows that the average shoreline retreat in the year of 2050 is about 94.71 meters and in 2100 is about 234.2 m. However, by using the method of Bruun Rule, the average shoreline retreat in the year of 2050 is about 161.27 m, and in the year of 2100 is about 349.16 m. The adaptation strategies that can be conducted to minimize the impacts are (i) protective pattern, (ii) accommodative pattern, and it is better to have a Strategic Area Construction Plan.
Authors: Khomsin
Abstract: Coastal areas often experience changes in function, region supposed to be conservation area or coastal protection forests, as water catchment areas and habitats of mangrove forests have been turned into region large-scale housing, residential, industrial, ware housing and so on. Coastal area of Surabaya, especially in the East Surabaya, the reclaimed much influenced by several factors, including results from land fill for various purposes (residential areas, factories, bussiness and etc.) and caused by the sedimentation of the estuary lead the emergence of mainland. The impact of the reclamation both landfill or natural sedimentation certainly have an impact on shoreline.Based on the explanation of the law of local government No. 23, 2014 Article 6 [1], the meant of shoreline is the boundary meeting between the highest sea level and the mainland. The use of shoreline in this provision is intended for the determination of the administrative area in the management marine areas. Where is the position of the East Surabaya shoreline recently?This paper will answer the question to determine the East Surabaya shoreline using tidal data, image satellite and Real Time Kinematic-Global Network Satellite System (RTK-GNSS). The result can be used by Surabaya Government to manage buffer and marine zone especially in the eastern part of Surabaya.
Authors: Engki Andri Kisnarti
Abstract: Ocean tides are the result of gravitational and centrifugal effect. Tidal motion in certain places does not only depend on the gravity moon and sun, but also by non-astronomical factors. The purpose of this study is to analyze the characteristics of the tides in Surabaya. The Methodology of this research are data collection, calculation using admiralthy methods, harmonic analysis, and trend analysis. The results showed that the waters of Surabaya has a type of tidal mixed semi diurnal. Results of the analysis of the tides in the Port of Perak shows there has been a rise in the function y = 0.0164 (x) + 156.86 every month from January 1994 - December 2009 or 1.97 mm per year. The lowest Mean Sea Level (MSL) occurred in January 1998, which is 141 cm. MSL in Surabaya unstable to Western Monsoon ends. The highest MSL occurs in transition between Eastern Monsoon towards the Western Monsoon, April 2008 amounted to 179 cm.
Authors: Muhammad Zikra
Abstract: A preliminary assessment of the available wave energy around Indonesia is presented. The computations have been conducted by using the wave data collected during 35 years period from 1980 to 2014 from European Centre for Medium-Range Weather Forecasts (ECMWF). Location situated in the south of Java Sea has the most promising location for wave power potential, with the highest energy resource available in the month of January to December. The yearly mean wave power is maximum at the Java sea can reach 22 kW/m.

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