ANALISIS PARAMETER ALFA HIDROGRAF SATUAN SINTETIK NAKAYASU PADA DAS DI PULAU FLORES - Krisnayanti, Denik S.; Frans, John H.; Halema, Emanuel U. M. (Jurnal Teknik Sipil, 2019)
Pulau Flores termasuk wilayah sungai strategis nasional sehingga perlu dikaji data karakteristik DAS sebagai dasar perhitungan debit banjir metode Hidrograf Satuan Sintetik (HSS) Nakayasu. Metode ini sederhana karena parameter inputnya sedikit. Namun penerapan HSS Nakayasu dijumpai kesulitan dalam penentuan parameter ? (alfa) yang bersifat perkiraan. Penelitian ini bertujuan mengetahui pengaruh bentuk DAS di pulau Flores terhadap nilai alfa menggunakan Sistem Informasi Geografis (SIG), mengetahui persamaan parameter alfa sesuai karakteristik DAS di pulau Flores, dan mengetahui besar koefisien determinasi dan standar error persamaan alfa yang diperoleh. Hasil penelitian menunjukkan pengaruh bentuk DAS berdasarkan SIG yaitu DAS memanjang dan kompleks menghasilkan kisaran nilai alfa 1,5 - 2. Adapun bentuk DAS radial dan paralel berkisar antara 2 - 3. Nilai alfa rata-rata DAS kompleks sebesar 1,783, DAS memanjang sebesar 1,928, DAS paralel sebesar 2,076, dan DAS radial sebesar 2,131. Persamaan parameter ? (alfa) hasil regresi non linear diperoleh ? = 0,47.A0,036. L0,597 / Tg. Koefisien determinasi sebesar 0,989. Standar error hasil estimasi sebesar 2%.Flores Island is included in the national strategic river area, so data on watershed characteristics need to be assessed as the basis for calculating the Synthetic Unit Hydrograph (SUH) Nakayasu method. This method is simple because the input parameters are few. However, the application of SUH Nakayasu was found to be difficult in determining the parameter ? (alpha) which is approximate. The study aims to determine the effect of Flores island watershed shape against alpha value using Geographic Information System (GIS), modeling the parameter equation alpha according to watershed characteristics on the island of Flores, and knowing the magnitude of the coefficient of determination and standard error of alpha equations obtained. The results showed the effect of the watershed shape based on GIS namely longitudinal and complex watershed produced a range of alpha values of 1.5 - 2. The the shape of radial and parallel watersheds ranged between 2 - 3. The average alpha value of complex watershed was 1,783, longitudinal watershed was 1,928, parallel watershed is 2,076, and radial watershed is 2,131. The equation ? (alpha) results of non linear regression are obtained ? = 0.47.A0.036. L0,597 / Tg. The determination coefficient is 0.989. Standard estimated error is 2%.