Electronic Theses and Dissertation

Banjir merupakan bencana alam yang sering terjadi di Indonesia. Umumnya kejadian banjir dapat diprediksi jika terjadi curah hujan yang tinggi di suatu kawasan dan berlangsung selama beberapa hari. Akan tetapi, banjir juga dapat terjadi secara tiba-tiba jika kawasan tersebut berada dalam ekosistem yang rusak. Saat ini kejadian banjir di Indonesia tergolong ekstrim. Salah satu daerah yang rawan terhadap banjir adalah Daerah aliran Sungai (DAS) Krueng Tamiang. DAS ini merupakan DAS terbesar di Provinsi Aceh dengan luas 4.826,56 Km2 dengan panjang sungai utama 217 km yang memiliki kapasitas infiltrasi tanah yang rendah pada musim penghujan, sehingga menyebabkan tingginya aliran permukaan yang dapat menimbulkan banjir. Dari permasalahan tersebut, maka penelitian ini bertujuan untuk mengetahui potensi luapan banjir dengan menggunakan pemodelan hidrodinamis 2D untuk berbagai skenario periode ulang debit banjir pada DAS Krueng Tamiang dan meninjau validasi model genangan banjir terhadap data lokasi banjir dari survey lapangan di DAS Krueng Tamiang berdasarkan banjir historis menggunakan Software Geo-HECRAS, serta mengetahui kondisi banjir (kedalaman dan luasan genangan banjir) pada kala ulang 2, 5, 10, 25, 50, dan 100 tahun. Dari hasil pemodelan didapatkan luas genangan banjir untuk setiap kala ulang sebagai berikut L2th = 43,373km2, L5th = 69,389 km2, L10th = 92,451 km2, L25th = 138,092 km2, L50th = 145,939 km2, dan L100th = 179,836 km2. Kedalaman genangan banjir berkisar 0 sampai dengan lebih dari 2 m. Hasil validasi genangan banjir dengan titik sebaran banjir menghasilkan informasi 10 titik berada pada area genangan banjir serta 2 titik tidak berada pada area genangan banjir.

Kata kunci: banjir, model genangan banjir, Geo-HECRAS

Flooding is a natural disaster that often occurs in Indonesia. Generally, flood events can be predicted if there is high rainfall in an area and it lasts for several days. However, floods can also occur suddenly if the area is in a damaged ecosystem. Currently, flood events in Indonesia are classified as extreme. One of the areas prone to flooding is the Krueng Tamiang watershed. This watershed is the largest watershed in Aceh Province with an area of 4,826.56 Km2 with a main river length of 217 km which has a low soil infiltration capacity in the rainy season, causing high surface flow that can cause flooding. From these problems, this study aims to determine the potential for flood overflow using 2D hydrodynamic modeling for various scenarios of flood discharge return periods in the Krueng Tamiang watershed and review the validation of the flood inundation model against flood location data from field surveys in the Krueng Tamiang watershed based on historical floods using Geo-HECRAS software, and determine flood conditions (depth and extent of flood inundation) at return periods of 2, 5, 10, 25, 50, and 100 years. The modeling results obtained the flood inundation area for each return period as follows L2th = 43.373 km2, L5th = 69.389 km2, L10th = 92.451 km2, L25th = 138.092 km2, L50th = 145.939 km2, and L100th = 179.836 km2. The depth of flood inundation ranges from 0 to more than 2 m. The validation results of flood inundation with flood distribution points resulted in information that 10 points were in the flood inundation area and 2 points were not in the flood inundation area. Keywords: flood, flood inundation model, Geo-HECRAS.