KAJIAN KERAWANAN LONGSOR TEBING BERDASARKAN KARAKTERISTIK GEOMORFOLOGI ALUR SUNGAI BENDO, KABUPATEN BANYUWANGI, PROVINSI JAWA TIMUR
REINETA PUSPITASARI, Prof. Dr. Junun Sartohadi, M.Sc
2016 | Skripsi | S1 GEOGRAFI DAN ILMU LINGKUNGANLongsor tebing merupakan salah satu proses geomorfologi yang dapat terjadi di tebing sungai. Lokasi penelitian berada di Sungai Bendo. Sungai Bendo merupakan sungai yang berhulu di Gunungapi Merapi, Rante, dan Ijen Muda, Kabupaten Banyuwangi, Provinsi Jawa Timur. Tujuan dari penelitian ini yaitu : (1) mengidentifikasi karakteristik fisik bagian hulu, tengah, dan hilir di Sungai Bendo (2) mengidentifikasi karakteristik longsor tebing di Sungai Bendo dan (3) menentukan kerawanan longsor tebing di Sungai Bendo. Penentuan zonasi Sungai Bendo berdasarkan karakteristik morfologi alur sungai, material penyusun, dan proses geomorfologi. Pengamatan dan survei lapangan diterapkan dalam penelitian untuk mengetahui karakteristik longsor tebing. Analisis terhadap kerawanan longsor tebing secara deskriptif dengan pengharkatan 4 parameter, yaitu kemiringan lereng tebing, tinggi tebing, penggunaan lahan, dan material penyusun tebing. Berdasarkan hasil penelitian, Sungai Bendo terbagi ke dalam tiga zonasi, yaitu hulu, tengah, dan hilir. Bagian hulu mengalami proses erosi secara vertikal, sehingga terbentuk lembah-lembah sungai yang dalam (baranco). Bagian tengah mempunyai kenampakan yang khas berupa lembah sungai berbentuk V melebar. Bagian hilir memiliki kenampakan relief secara makro berupa datar-landai dengan proses erosi secara lateral, sehingga lembah sungai U melebar. Longsor tebing di Sungai Bendo dipengaruhi kondisi morfologi dan material penyusun tebing. Tipe longsor tebing berupa robohan, jatuhan, longsoran translasional, dan rotasional dengan dominasi longsoran translasional berjumlah 41 kejadian. Kerawanan longsor tebing diklasifikasikan ke dalam kelas rendah, agak rendah, sedang, dan tinggi. Kerawanan tinggi banyak dijumpai pada segmen sungai bagian atas (segmen 1, 2, dan 4) karena pengaruh kondisi kemiringan lereng tebing >45%, tinggi tebing >10 meter, penggunaan lahan berupa sawah atau permukiman dengan material penyusun tebing berupa consolidated material (breksi) dan unconsolidated material (andesit dan breksi)
Riverbank failure is one of the geomorphic processes that could occur in river bank. The study was located at Bendo River that was disgorged from Ijen Muda Volcano, Merapi Volcano and Rante Volcano. The aim of this research were (1) to identify the physical characteristic of upstream, middle, and downstream section of Bendo River (2) to identify the riverbank failure characteristic of Bendo River and (3) to determine the riverbank failure susceptibility of Bendo River. The zonation of Bendo River was made based on its morphological characteristic, material, and geomorphology process. The research was conducted using an observation and field survey to understand riverbank characteristic. Riverbank failure's analysis has been done by descriptive method. Riverbank failure susceptibility determination is was accomplished by parametric scoring, which were bank angle, bank height, bank material, and landuse. Based on this research, Bendo River divided into three sections, upstream, middle, and downstream. In upstream section erosion process occured vertically, thus forming deep river valleys (Baranco). Bendo River's middle section has V- shaped valley widens. The downstream has flat-sloping macro relief with lateral erosion processes which forming U-shaped valleys. Riverbank failure in Bendo River was affected by morpohological characteristic and bank material. Riverbank failure's types that have been identified were topples, rockfalls, translational slides, and rotational slide. The highest rate was translational slide by 41 events. Riverbank failure susceptibility along its river bank was classified to 4 classes, low, rather low, medium, and high. The highest riverbank failure susceptibility on the upper of river segment (1st, 3rd, and 4th segments) was caused by its bank angle >45 %, bank height >10 meter, the landuse of paddy field and settlement, and its consolidated material (breccia) and unconsolidated material (andesite and breccia).
Kata Kunci : Longsor tebing, Zonasi sungai, Kerawanan longsor tebing/Riverbank failure, river zonation, riverbank failure susceptibility
