ANALISA PENGARUH PENEMPATAN KRIB TERHADAP DISTRIBUSI SEDIMEN DI PERTEMUAN SUNGAI GARANG DAN KREO
Abstract
Abstrak: Sedimentasi dan erosi yang disebabkan oleh perbedaan debit merupakan masalah yang sering terjadi di pertemuan Sungai Garang dan Kreo. Penempatan bangunan krib eksisting belum berfungsi optimal sebagai pengatur arah arus sungai. Tujuan penelitian ini untuk mengetahui kecepatan maksimum, tegangan geser dasar sungai dan distribusi sedimen terhadap pengaruh penempatan krib. Simulasi menggunakan modul RMA2 untuk mengetahui hidrodinamika aliran dengan debit banjir rancangan kala ulang 50 tahun dan simulasi modul SED2D untuk mengetahui distribusi sedimen. Kedua simulasi tersebut digunakan pada 3 (tiga) skenario. Agar mendapatkan tingkat keakuratan model terhadap kondisi lapangan maka dilakukan uji MRE (Mean Relative Error) sebesar 0,91% sebagai indikasi parameter proses kalibrasi model numerik 2 dimensi. Penempatan krib yang lebih efektif adalah skenario yang ketiga dengan distribusi kecepatan maksimum 1,75 m/dtk, tegangan geser ( Æ® ) maksimum 8,65 N/m2 dan sedimentasi terjadi didaerah sekitar krib, erosi pada arah tanggul kanan penampang sungai yang sering terjadi sedimentasi.
Kata kunci : Pertemuan sungai, krib, sedimentasi, erosi.
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Abstract: Sedimentation and erosion caused by differences discharge is a problem that often occurs at the confluence of the Garang and Kreo rivers. The placement of existing groynes has not optimally functioned to regulate the river flow direction. The goal of this analysis is to find out the maximum velocity, bed shear, and sediment distribution towards the effect of groyne placement. The Simulation using the RMA2 module to find out the flow hydrodynamics with the discharge from constructed 50-year floods and the simulation using SED2D module to find out the sediment distribution. It simulations is used for three scenarios. To maintain accuracy of the model towards field conditions, a Mean Relative Error (MRE) test of 0.91% was conducted as the parameter indication of the 2-dimensional numerical model calibration process. The most effective groyne placement is third scenario with a maximum velocity distribution of 1.75 m/s, maximum riverbed bed shear (Æ®) of 8.65 N/m2 and sedimentation only occurring in the areas around the groynes, while erosion occurred on the dikes of the right-hand side of the river where sedimentation often occurs.
Keywords : River confluence, groynes, sedimentation, erosion
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