MODEL NUMERIK DISPERSI SEDIMEN AKIBAT PASANG SURUT DI PANTAI

Abstract

This research discusses the suspended sediment distribution on the coastal water of the East Flood way Semarang. These distribution of the suspended sediment are discussed in relation to their transportation by the hidrodinamical modelling within this research area. The numerical distribution of the suspended sediment on these coastal regions was built up by consolidation method on the horizontal 2 dimension transport QUICKEST equation and the two step semi — implicit hidrodinamically modelling. Scenario to run this model was done by simulation of the initial uniform value of the tidal currents. The initial value of the suspended concentrarion was determined from the field observation at the river mouth (S1) wich was considered as a source . The stations of the field observation were located at mount of 17 location with started from the river mouth (S1) toward the offshore ( from S2 until S17). The distribution pattern of the suspended sediment concentration resulted both from field observation and simulation modelling,to diverse to the offshore direction.The maximum concentration was founded at the river mouth (resource) of the East Flood way system,the value were 1,2652 gr/1 and 0,6547 gr/1 which were obtained from laboratory observation and model simulation respectively, The minimum concentration were 0,3646 gr/l, and 0,4987 gr/1 which were obtained from laboratory observation and model respectively. It is expected that the researh can be concluded that the numerical model dispertion sediment of the coastal water of the East Flood way Semarang. The related intitution may use this model to overcome the problem of sedimentation around the east floody way mouth. Penelitian yang telah dilakukan adalah membahas mengenai studi penyebaran sedimen tersuspensi di perairan Pantai Banjir Kanal Timur Semarang dengan menggunakan model numerik dispersi sedimen tersuspensi di perairan pantai.Model numerik dispersi sedimen tersuspensi diperairan pantai ini dibangun dari persamaan transpor 2-dimensi horizontal QUICKEST yang digabungkan dengan model hidrodinamika semi implisit dua langkah. Skenario untuk menjalankan model dilaksanakan secara simulasi dari arus pasang surut dengan nilai seragam. Nilai awal konsentrasi sedimen tersuspensi (initial value) tersuspensi ditentukan dari hasil pengamatan lapangan yaitu pada muara sungai (Stasiun S1).yang dianggap sebagai titik sumber sedimen tersuspensi. Pengamatan dilapangan dilakukan pada 17 stasiun yang dimulai dari muara sungai (S1) menuju lepas pantai (S2 sampai dengan S17 ) . Pola sebaran sedimen tersuspensi yang diperoleh dari pengamatan lapangan dan berdasarkan hasil model menunjukan bahwa konsentrasi sedimen tersuspensi konsentrasinya semakin mengecil menuju kearah lepas pantai,konsentrasi maksimum berada disekitar sumber (muara sungai) . Konsentrasi maksimum dijumpai disekitar mulut sungai (sumber) dari sistem aliran sungai Banjir Kanal Timur Semarang, konsentrasi sebesar ,2652 gr/I yang diperoleh dari hasil pengatan laboratorium dan simulasi model 0,6457 gr/I, sedangkan konsentrasi minimum berada pada stasiun di lepas pantai dengan nilai dari hasil pengamatan 0,3646 gr/I dan yang dihasilkan dari simulasi model numerik dispersi sedimen tersuspensi di perairan pantai. Dad hasil penelitian diharapkan model ini bisa bermanfaat bagi pihak yang berkepentingan untuk penanganan sedimen diperairan Banjir kanal timur Semarang.dengan rekomendasi meminimalkan transport sedimen dari sistim sungai yang ada.