Model Hidrologi Terdistribusi untuk Simulasi Hidrograf Banjir Menggunakan Data Radar
DOI:
https://doi.org/10.5614/jts.2019.26.3.9Keywords:
Model hidrologi hujan-aliran terdistribusi, hujan radar, hidrograf satuan ModClark, kalibrasi.Abstract
Abstrak
Penerapan model hidrologi hujan-aliran terdistribusi sebagai bagian penting dari sistem peringatan dini banjir di wilayah lereng Gunung Merapi, membutuhkan input data hujan dengan resolusi spasial yang memadai. Oleh karena itu penggunaan data hujan dari ARR yang memiliki resolusi spasial yang rendah akan menyebabkan hasil hitungan hujan rata-ratanya (DAS) menjadi kurang teliti. Alternatif yang dapat dilakukan adalah menggunakan data hujan radar yang memiliki resolusi spasial dan temporal yang jauh lebih baik dibandingkan ARR. Pada penelitian ini dilakukan kajian hasil hitungan hidrograf banjir di wilayah lereng Gunung Merapi. Pemodelan hujan-aliran secara terdistribusi dilakukan dengan menentukan resolusi grid dari DAS dengan titik tinjau hitungan pada pos AWLR. Hujan pada setiap grid DAS dihitung sebagai rata-rata data hujan radar semua piksel di area masing-masing grid DAS. Simulasi limpasan permukaan DAS menggunakan paket perangkat lunak WMS v.10.1 dengan metode Hidrograf Satuan ModClark. Evaluasi ketelitian hidrograf banjir hasil simulasi didasarkan pada indikator kesalahan relatif debit puncak (peak discharge), waktu puncak (time to peak) dan volume limpasan permukaan (direct runoff volume). Hasil hitungan simulasi limpasan permukaan DAS menunjukkan bahwa perlu dilakukan telaah yang rinci terhadap faktor losses dan kesesuaian parameter hidrograf satuan, untuk menghasilkan kalibrasi model yang akurat.
Abstract
The application of the distributed rainflow-runoff hydrological model as an important part of the early flood warning system in the slopes of Mount Merapi, requires rainfall data input with adequate spatial resolution. Therefore, the use of rainfall data from ARR which has a low spatial resolution will cause the results of the average rainfall (watershed) to be less precise. An alternative that can be done is to use radar rainfall data that has a far better spatial and temporal resolutions than the data from ARR. In this research, a study of the results of the flood hydrograph calculation in the slopes of Mount Merapi was conducted. The distributed rainflow-runoff modeling was done by determining the grid resolution of the watershed with a reference point of the calculation in the AWLR. Rain on each watershed grid was calculated as the average radar rainfall data of all pixels in the area of each watershed grid. Watershed surface runoff simulation used the WMS v.10.1 software package with the ModClark Unit Hydrograph method. The evaluation of the flood hydrograph simulation results' accuracy was based on indicators of the relative error of peak discharge, time to peak and direct runoff volume. The results of the watershed surface runoff simulation showed that a detailed study of the loss factors and the compatibility of the unit hydrograph parameter is necessary to produce an accurate model calibration.
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