ANALISA PREDIKSI SEDIMENTASI PADA DAS METRO KOTA MALANG DENGAN METODE HEC-RAS

Abstract

ABSTRAK

DAS Metro adalah merupakan daerah yang rawan terjadi tanah longsor dan banjir, peristiwa itu terjadi karena mengingat di sepanjang DAS berdiri perumahan padat penduduk mengakibatkan lebar sungai mengalami penyempitan dan pendangkalan yang apabila terjadi penambahan debit air yang tinggi secara tiba-tiba tentu membuat air tersebut meluap ke perkampungan penduduk. Tujuan dari penelitihan ini untuk mengetahui besar debit aliran sungai, mengetahui nilai rata- rata sedimentasi, karekteristik sedimen, dan terakhir untuk mengetahui rata- rata nilai angkutan sedimen. HEC-RAS merupakan aplikasi (software) untuk memodelkan aliran di sungai, satu dimensi aliran permanen maupun tak permanen (steady and unsteady onedimensional flow model). Dari perhitungan didapatkan nilai angkutan sedimen di titik A diperoleh hasil 3,997 m3/det/m, di titik B diperoleh hasil 7,111 m3/det/m, di titik C diperoleh hasil 4,721, dan di titik D diperoleh hasil 5,952. Dari kedua nilai angkutan sedimen tersebut rata-rata nilai angkutan sedimen di Sungai Metro sebesar 5,455 m3/det/m. Pengaruh sedimen yang berpindah mengakibatkan sungai menjadi lebih dalam. Angkutan sedimen juga meningkat seiring panjangnya sungai dapat dilihat perbandingan pada STA 0+000 hingga STA 4+300. Dari hasil running simulasi sedimen menggunakan program HEC-RAS dapat dilihat bahwa pada sungai Metro pergerakan angkutan sedimen mengarah pada proses Erosi.

Kata Kunci : Sedimentasi, HEC-RAS, Debit Aliran, Sungai Metro Malang.

                                                   ABSTRACT                                             

The Metro watershed is an area that is prone to landslides and floods, this incident occurred because along the watershed there were dense housing estates, resulting in narrow and shallow river widths which if there was a sudden addition of high water discharge, of course, the water overflowed. to populated villages. The purpose of this study was to determine the amount of river flow discharge, to determine the average value of sedimentation, sediment characteristics, and finally to determine the average value of sediment transport. HEC-RAS is an application (software) for modeling flow in rivers, one-dimensional permanent flow or non-permanent (steady and non-steady one-dimensional flow models). From the calculation, it is obtained that the sediment transport value at point A is 3,997 m3/s/m, at point B the results are 7,111 m3/s/m, at point C the results are 4,721, and at point D the results are 4,721. 5,952 results were obtained. From the two values of sediment transport, the average value of sediment transport in the Metro River is 5,455 m3/s/m. The influence of moving sediment causes the river to become deeper. Sediment transport also increases with the length of the river that can be seen compared to STA 0+000 to STA 4+300. From the simulation results of running sediment using the HEC-RAS program, it can be seen that in the Metro river the movement of sediment transport leads to the erosion process.

Key Words : Sedimentation, HEC-RAS, Flow Discharge, Metro Malang River