PENGGUNAAN MODEL GEOMORPHOLOGICAL INSTANTANEOUS UNIT HYDROGRAPH UNTUK MENENTUKAN HIDROGRAF LIMPASAN LANGSUNG Studi Kasus Daerah Aliran Sungai Opak Kota Yogyakarta USE OF INSTANTEOUS HYDROGRAPH UNIT GEOMORPHOLOGICAL MODELS TO DETERMINE DIRECT RUN-OVER HYDROGRAPH Case Study of the Opak Watershed in the City of Yogyakarta

Hendrasari, Ratna Septi and Zulfahmi, Zakky (2023) PENGGUNAAN MODEL GEOMORPHOLOGICAL INSTANTANEOUS UNIT HYDROGRAPH UNTUK MENENTUKAN HIDROGRAF LIMPASAN LANGSUNG Studi Kasus Daerah Aliran Sungai Opak Kota Yogyakarta USE OF INSTANTEOUS HYDROGRAPH UNIT GEOMORPHOLOGICAL MODELS TO DETERMINE DIRECT RUN-OVER HYDROGRAPH Case Study of the Opak Watershed in the City of Yogyakarta. ["eprint_fieldopt_thesis_type_tugasakhir" not defined] thesis, University Technology Yogyakarta.

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Abstract

Untuk melakukan pemodelan hidrograf limpasan langsung menggunakan metode hirograf satuan pada suatu daerah aliran sungai (DAS) dibutukan data hujan dan aliran. Apabila di suatu daerah aliran sungai (DAS) tidak tersedia data hujan dan data aliran yang memadai, maka penetapan hidrograf satuan secara analitis tidak dapat dilakukan. Permasalahan tersebut mendorong kajian penggunaan model Geomorphological Instantaneous Unit Hydrograph (GIUH) untuk hitungan hidrograf limpasan langsung dengan menggunakan pendekatan Sistem Informasi Geografis (SIG) yang dapat menentukan parameter fisik DAS. Penelitan hidrograf satuan model GIUH dilakukan dengan menentukan parameter fisik DAS. Parameter fisik DAS diperoleh dari data ASTER Global DEM V2 yang diolah dengan menggunakan perangkat lunak Watershed Modeling System dan Arcmap. Metode model Nash dan kurva-s digunakan untuk mengolah GIUH sehingga menjadi Hidrograf Satuan Sesaat dan Hidrograf Satuan (UH) per jam, yang kemudian akan dibandingkan dengan hidrograf satuan terukur metode Collins. Analisis sensitifitas morfologi DAS dilakukan pada parameter waktu konsentrasi (tc), rasio panjang (Rʟ), rasio cabang (Rʙ), rasio luas (Rᴀ) dan faktor k model Nash. Hasil pemodelan GIUH yang dilakukan pada DAS AWLR Pogung menjukkan bahwa nilai qₚ lebih kecil dibandingkan hidrograf satuan terukur, sedangkan tₚ dan tb yang lebih lambat dan panjang. Hal ini diakibatkan oleh jaringan sungai yang dimodelkan tidak sesuai dengan jaringan sungai sesungguhnya pada DAS AWLR Pogung, dan sedikitnya kasus yang bisa digunakan akibat keterbatasan data. Hasil analisis sensitifitas morfologi DAS berupa rasio percabangan (Rʙ), rasio luas (Rᴀ), dan rasio panjang (Rʟ), faktor k model Nash serta tc yang digunakan berpengaruh terhadap bentuk GIUH yang dihasilkan, dimana penggunaan tc yang dihitung menggunakan metode Kirpich modified memiliki akurasi yang lebih baik dibandingkan dengan metode ventura dan metode Kirpich. Kata kunci: Hidrograf Model GIUH, Limpasan Langsung, Sungai Opak  In order to model the direct runoff hydrograph using the unit hydrograph method in a watershed (DAS), rainfall and flow data are needed. If in a watershed (DAS) there are no adequate rainfall data and flow data, then the determination of the unit hydrograph analytically cannot be carried out. These problems have prompted studies on the use of the Geomorphological Instantaneous Unit Hydrograph (GIUH) model to calculate direct runoff hydrographs using a Geographic Information System (GIS) approach that can determine the physical parameters of a watershed. Research on the GIUH model unit hydrograph was carried out by determining the physical parameters of the watershed. The physical parameters of the DAS were obtained from ASTER Global DEM V2 data which were processed using the Watershed Modeling System and Arcmap software. The Nash model method and s-curve are used to process the GIUH so that it becomes a Momentary Unit Hydrograph and Unit Hydrograph (UH) per hour, which will then be compared with the measured unit hydrograph using the Collins method. Sensitivity analysis of watershed morphology was carried out on the parameter concentration time (tc), length ratio (Rʟ), branch ratio (Rʙ), area ratio (Rᴀ) and the k factor of the Nash model. The results of the GIUH modeling carried out on the Pogung AWLR watershed show that the value of qₚ is smaller than the measured unit hydrograph, while tₚ and tb are slower and longer. This is caused by the river network being modeled does not match the actual river network in the Pogung AWLR watershed, and there are only a few cases that can be used due to data limitations. The results of the sensitivity analysis of watershed morphology in the form of branching ratio (Rʙ), area ratio (Rᴀ), and length ratio (Rʟ), the k factor of the Nash model and the tc used have an effect on the resulting GIUH shape, where the use of tc calculated using the modified Kirpich method has better accuracy than venture method and Kirpich method. Keywords: GIUH Model Hydrograph, Direct Runoff, Opak River

Item Type: Thesis (["eprint_fieldopt_thesis_type_tugasakhir" not defined])
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Fakultas Sains dan Teknologi > S1 Teknik Sipil
Depositing User: Kaprodi S1 Teknik Sipil UTY
Date Deposited: 19 Apr 2024 01:40
Last Modified: 19 Apr 2024 01:40
URI: http://eprints.uty.ac.id/id/eprint/15289

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