Electronic Theses and Dissertation

Sedimentasi merupakan suatu peristiwa penumpukan atau pengendapan material di suatu tempat yang diangkut oleh tenaga air maupun angin. Sedimentasi sering terjadi di alur Sungai Krueng Langsa. Sedimentasi ini mengurangi kapasitas tampungan sungai, yang dapat menyebabkan banjir. Penelitian ini bertujuan untuk memahami bentuk kurva rating curve sedimen dan model angkutan sedimen yang terjadi di Sungai Krueng Langsa. Data yang digunakan dalam penelitian ini diantaranya data sampel sedimen dasar, sampel sedimen melayang, hidrometri, debit banjir rencana, geometri sungai, dan kekasaran sungai. Penelitian ini memodelkan angkutan sedimen yang terjadi pada Sungai Krueng Langsa menggunakan aplikasi HEC-RAS 6.1. Hasil penelitian diperoleh nilai τ_0 > τ_c yang mengindikasikan terjadinya angkutan dan pergerakan sedimen di Sungai Krueng Langsa. Dari grafik rating curve sedimen diperoleh persamaan regresi senilai Qs = 0,053Qw2 + 131,86Qw (hulu), Qs= -0,0134Qw2 + 140,6Qw (tengah), dan Qs = 0,0002Qw2 + 5,5176Qw (hilir). Nilai koefisien determinasi (R2) masing-masing sebesar 0,9406 (hulu), 0,9252 (tengah), dan 0,9998 (hilir) nilai korelasi tersebut termasuk dalam kategori sangat baik karena mendekati 1. Hasil dari model angkutan sedimen berupa perubahan dasar sungai akibat pergerakan sedimen. Pada titik tinjauan bagian hulu, yaitu RS 297 terjadi agradasi setinggi 0,3975 m. Pada titik tinjauan bagian tengah, yaitu RS 279 terjadi degradasi setinggi 0,5038 m. pada titik tinjauan bagian hilir, yaitu RS 230 terjadi degradasi sebesar 0,9167 m. Agradasi ekstrem terjadi pada RS 337 setinggi 2,2498 m. Degradasi esktrem terjadi pada RS 286 setinggi 2,0739 m.

Kata kunci: Sungai Krueng Langsa, angkutan sedimen, rating curve, agradasi dan degradasi, HEC-RAS.

Sedimentation is an event of accumulation or deposition of material in a place that is transported by water or wind power. Sedimentation often occurs in the Krueng Langsa River channel. This sedimentation reduces the river's storage capacity, which can cause flooding. This research aims to understand the shape of the sediment rating curve and the sediment transport model that occurs in the Krueng Langsa River. The data used in this research include data on basic sediment samples, floating sediment samples, hydrometry, planned flood discharge, river geometry, and river roughness. This research models sediment transport that occurs in the Krueng Langsa River using the HEC-RAS 6.1 application. The research results obtained a value of τ_0 > τ_c which indicates the transport and movement of sediment in the Krueng Langsa River. From the sediment rating curve graph, the regression equation obtained is Qs = 0.053Qw2 + 131.86Qw (upstream), Qs = -0.0134Qw2 + 140.6Qw (middle), and Qs = 0.0002Qw2 + 5.5176Qw (downstream). The coefficient of determination (R2) values are respectively 0.9406 (upstream), 0.9252 (middle), and 0.9998 (downstream). These correlation values are included in the very good category because they are close to 1. The results of the sediment transport model are changes river bed due to sediment movement. At the upstream viewing point, namely RS 297, there is aggradation as high as 0.3975 m. At the middle observation point, namely RS 279, degradation as high as 0.5038 m occurred. At the downstream viewing point, namely RS 230, degradation of 0.9167 m occurred. Extreme aggradation occurs on RS 337 as high as 2.2498 m. Extreme degradation occurred at RS 286 as high as 2.0739 m. Keywords: Krueng Langsa River, sediment transport, rating curve, aggradation and degradation, HEC-RAS.