Zulvan,, Muhammad Ridwan (2023) Studi Morfodinamika Muara Sungai Serayu oleh Pengaruh Arus akibat Gelombang, Arus Pasang Surut, dan Arus Sungai,. Sarjana thesis, Universitas Brawijaya.
Abstract
Muara Sungai Serayu di Kabupaten Cilacap mengalami perubahan morfologi berupa pembentukan sand bars di mulut sungai. Selama musim kering, sand bars meluas dan mengurangi kemampuan mulut sungai dalam melimpaskan aliran sungai ke arah laut sehingga riskan menyebabkan banjir yang merugikan daerah sawah irigasi, permukiman, dan PLTU di sekitar muara sungai. Sementara itu, selama musim hujan, sand bars perlahan tererosi dan luasannya berkurang kembali. Berdasarkan kondisi tersebut, penelitian ini bertujuan untuk menganalisis pola arus dan perubahan morfologi di Muara Sungai Serayu sehingga dapat dirumuskan solusi struktural yang sesuai untuk penanganan permasalahan. Pada penelitian ini, dilakukan pemodelan numerik menggunakan perangkat lunak untuk memodelkan domain eksisting dengan kondisi musim kering dan domain eksisting dengan kondisi musim hujan. Domain yang dibuat mencakup wilayah sungai dengan panjang 10 km dari mulut sungai dan wilayah laut hingga 10 km dari mulut sungai. Data kedalaman yang digunakan didapat dari hasil survei pada tahun 2021 serta elevasi BATNAS, dan DEMNAS yang akan diolah menjadi data batimetri domain eksisting. Data debit diperoleh dari data debit pengukuran sesaat di Bendung Gerak Serayu selama 10 tahun untuk kemudian dioah menjadi data debit andalan. Untuk musim kering digunakan data debit konstan 36,14 m3/det dan untuk musim hujan digunakan seri debit hidrograf dari HSS Snyder-Alexeyev. Data gelombang diolah dari data angin selama 10 tahun yang kemudian dilakukan pengolahan wave hindcasting metode SPM 1984. Data gelombang yang digunakan untuk kondisi musim kering adalah gelombang dengan tinggi signifikan 2,39 m dan periode 7,97 detik dari arah tenggara, sedangkan untuk kondisi musim hujan digunakan tinggi signifikan 0,84 m dan periode 4,68 detik dari arah barat daya. Data ketinggian muka air akibat pasang surut diperoleh dari stasiun pengukuran CCAP di Teluk Cilacap. Simulasi dilakukan selama dua hari untuk masing-masing kondisi eksisting dengan warmup selama dua hari. Hasil simulasi domain eksisting kondisi musim kering menunjukkan pola arus di wilayah sungai mengarah ke arah hulu hingga 8,6 km ketika terjadi pasang dan mengarah ke hilir ketika surut. Pada kondisi musim kering terjadi penambahan elevasi dasar di ujung sand bars hingga 0,20 m akibat kecepatan arus longshore yang menurun di ujung sand bars karena terpengaruh aliran sungai. Sementara itu, hasil simulasi domain eksisting kondisi musim hujan menunjukkan arah arus di wilayah sungai yang selalu mengarah ke hilir baik ketika pasang, maupun surut. Kecepatan arus yang menabrak sand bars berkisar antara 0,50 – 1,20 m/det yang menyebabkan erosi pada ujung sand bars sehingga elevasi dasar berkurang hingga 1,30 m. Perluasan sand bars di musim kering perlu dicegah untuk tetap menjaga kapasitas mulut sungai dalam melimpaskan debit sehingga ditentukan solusi struktural berupa jetty di sebelah timur mulut sungai dengan elevasi puncak mercu +4,10 m di atas MSL, kemiringan 1:2, bahan tetrapod, dan panjangnya ditarik dari garis pantai hingga kedalaman 5 m. Hasil simulasi domain dengan jetty selama dua hari dengan kondisi musim kering menunjukkan sedimentasi yang berkisar 0,00 – 0,05 m di ujung sand bars sehingga cukup signifikan dalam mencegah perluasan sand bars.
English Abstract
Serayu River located in the Cilacap Regency has experienced morphological changes in the form of the formation of sand bars at the river mouth. During the dry season, the sand bars expand and reduce the ability of the river mouth to discharge the river flow towards the sea so that it is at risk of causing floods that harm irrigated rice fields, settlements, and power plants around the river mouth. Meanwhile, during the rainy season, the sand bars are slowly eroded and the area is reduced again. Based on these conditions, this study aims to analyze current patterns and morphological changes in the Serayu River Estuary so that appropriate structural solutions can be formulated for handling the problem. In this study, numerical modeling was conducted using software to model the existing domain under dry season conditions and the existing domain under wet season conditions. The domain includes the river area with a length of 10 km from the river mouth and the sea area up to 10 km from the river mouth. The depth data used is obtained from survey results in 2021 as well as the elevations of BATNAS and DEMNAS which will be processed into existing domain bathymetry data. Discharge data is obtained from instantaneous measurement discharge data at the Serayu Motion Weir for 10 years and then processed into dependable discharge data. For the dry season, constant discharge data of 36.14 m3/sec is used and for the rainy season, the hydrograph discharge series from the Snyder-Alexeyev Syntethic Unit Hydrograph is used. Wave data is processed from wind data for 10 years which is then processed wave hindcasting SPM 1984 method. Wave data used for dry season conditions are waves with a significant height of 2.39 m and a period of 7.97 seconds from the southeast, while for wet season conditions a significant height of 0.84 m and a period of 4.68 seconds from the southwest are used. Water level data due to tides was obtained from the CCAP measurement station in Cilacap Bay. Simulations were conducted for two days for each existing condition with warmup for two days. The simulation results of the existing domain under dry season conditions show that the current pattern in the river area is directed upstream up to 8.6 km during high tide and downstream during low tide. In dry season conditions, there is an increase in the bottom elevation at the end of the sand bars up to 0.20 m due to the longshore current velocity slowing down at the end of the sand bars due to the influence of river flow. Meanwhile, the simulation results of the existing domain under wet season conditions showed that the current direction in the river area was always directed downstream during both high and low tides. The velocity of the current hitting the sand bars ranged from 0.50 - 1.20 m/sec which caused erosion at the toe of the sand bars resulting in a reduced base elevation of up to 1.30m. The expansion of the sand bars in the dry season needs to be prevented to maintain the capacity of the river mouth to discharge, so a structural solution was determined in the form of a jetty to the east of the river mouth with a lighthouse peak elevation of +4.10 m above MSL, a slope of 1:2, tetrapod material, and a length drawn from the shoreline to a depth of 5 m. Domain simulation results with the jetty for two days under dry season conditions showed sedimentation ranging from 0.00 - 0.05 m at the toe of the sand bars, which was significant in preventing the expansion of the sand bars.
| Item Type: | Thesis (Sarjana) |
|---|---|
| Identification Number: | 0523070075 |
| Uncontrolled Keywords: | morfodinamika, pola arus, muara sungai, jetty |
| Divisions: | Fakultas Teknik > Teknik Sipil |
| Depositing User: | agung |
| Date Deposited: | 12 Jan 2024 03:47 |
| Last Modified: | 12 Jan 2024 03:47 |
| URI: | http://repository.ub.ac.id/id/eprint/209037 |
![[thumbnail of M. RIDWAN ZULVAN.pdf]](http://repository.ub.ac.id/style/images/fileicons/text.png) |
Text
M. RIDWAN ZULVAN.pdf Restricted to Repository staff only until 31 December 2025. Download (16MB) |
Actions (login required)
 |
View Item |