Modeling of Event and Continuous Flow Hydrographs with WMS and HEC-HMS Using Ground and Satellite Rainfall Data Case Study in the Code and Gajahwong River Basin, Yogyakarta, Indonesia

Teng, Teu, Prof. Ir. Joko Sujono, M. Eng., Ph.D.; Ir. Rachmad Jayadi, M. Eng., Ph.D.

2020 | Tesis | MAGISTER TEKNIK PENGELOLAAN BENCANA ALAM

Simulasi hidrograf banjir dan aliran kontinyu umumnya diperkirakan untuk kesiapan banjir yang lebih baik, pengurangan daya rusak banjir dan pengelolaan air. Secara historis, Sungai Code dan Gajahwong sering mengalami banjir yang merusak beberapa rumah di sepanjang sungai. Menanggapi masalah ini, tujuan utama dari penelitian ini adalah (1) untuk mensimulasikan hidrograf banjir dan aliran kontinyu dari dua daerah tangkapan air tersebut menggunakan data pengukuran curah hujan di lapangan dan data satelit PERSIANN-CCS; (2) untuk membandingkan hidrograf banjir dan aliran kontinyu yang didapatkan berdasar dua jenis data curah hujan, yaitu pengukuran lapangan dan satelit curah hujan PERSIANN-CCS. Dalam penelitian ini, perangkat lunak Watershed Modeling System (WMS) 10.1 diintegrasikan dengan model hidrologi HEC-HMS, diterapkan untuk mensimulasikan hidrograf banjir dan aliran kontinyu di DAS Code dan DAS Gajahwong. Loss method Gridded SCS Curve Number dan metode transformasi ModClark diterapkan untuk mensimulasikan hidrograf banjir. Sementara itu, metode transformasi hidrograf satuan Clark dan loss method Soil Moisture Accounting diterapkan untuk mensimulasikan aliran kontinyu di DAS. Data curah hujan satelit harian dan harian dan PERSIANN diterapkan untuk mensimulasikan hidrograf banjir dan aliran kontinu secara teratur. Hasilnya, itu menunjukkan bahwa kinerja hasil simulasi hidrograf banjir kedua penggunaan curah hujan tidak cocok yang menunjukkan debit puncak lebih rendah dibandingkan dengan data debit yang diamati, tetapi melakukan sangat baik setelah kalibrasi yang menampilkan kesalahan relatif kecil 0,33% dari curah hujan tanah untuk baik Code dan Gajahwong basin, dan 0,11% dan 0,60% dari penggunaan curah hujan satelit PERSIANN-CCS untuk masing-masing basin Code dan Gajahwong. Untuk aliran kontinu, hasil kinerja kalibrasi hasil aliran kontinu menggunakan curah hujan harian di tanah berada di peringkat puas yang memiliki NSE = 0,572, RSR = 0,7, PBIAS = -8% di Code basin dan peringkat tidak puas memiliki NSE = -1,476, RSR = 1.6, PBIAS = -71.05% untuk penggunaan curah hujan harian di cekungan Gajahwong. Secara komparatif, hasil kalibrasi hidrograf banjir menunjukkan bahwa curah hujan satelit PERSIANN-CCS menghabiskan waktu lebih singkat 1 jam untuk mencapai puncak buangan dibandingkan dengan curah hujan tanah karena karakteristik curah hujan yang berbeda. Sementara itu, hasil aliran kontinu dari tanah harian dan penggunaan curah hujan satelit PERSIANN-CCS dilakukan tidak dapat diterima untuk cekungan Gajahwong, kecuali Cekungan kode yang menunjukkan hasil yang dapat diterima dengan menggunakan curah hujan harian berdasarkan indikator statistik (NSE, RSR dan PBIAS).

Flood hydrograph and continuous flow simulations are commonly estimated for better flood preparedness, flood damage reduction and water supply. Historically, the Code and Gajahwong rivers have often experienced flooding which has damaged several houses along the river. Responding to this problem, the main objectives of this study are (1) to simulate flood hydrograph and continuous flow of these two basins using ground and PERSIANN-CCS satellite rainfall; (2) to compare flood hydrograph and continuous flow result between two types of rainfall usages, i.e. ground and PERSIANN-CCS satellite rainfall. In this study, Watershed Modelling System (WMS) 10.1 software integrated with hydrological model of HEC-HMS was applied to simulate flood hydrograph and continuous flow in Code and Gajahwong river basin. Gridded SCS Curve Number of loss method and ModClark of transform method were applied to simulate flood hydrograph. Meanwhile, Clark unit hydrograph of transform method and soil moisture accounting of loss method were applied to simulate continuous flow in the watersheds. Hourly and daily of ground and PERSIANN satellite rainfall data were applied to simulate flood hydrograph and continuous flow orderly. As result, the result showed that the performance of flood hydrograph simulation both rainfall usages were not well-fit which showed the lower peak discharge comparing to observed discharge data, but performed very good after calibration which displayed small relative error 0.33% of ground rainfall for both Code and Gajahwong basin, and 0.11% and 0.60% of PERSIANN-CCS satellite rainfall usage for Code and Gajahwong basin respectively. Moreover, the calibration performance of continuous flow result using daily ground rainfall was in satisfied ranking which having NSE= 0.572, RSR= 0.7, PBIAS= -8% at Code basin and unsatisfied ranking having NSE= -1.476, RSR= 1.6, PBIAS= -71.05% for daily ground rainfall use at Gajahwong basin. Comparatively, the flood hydrograph calibration result showed that PERSIANN-CCS satellite rainfall spent shorter time 1 hour to reach the peak discharge comparing to ground rainfall due to different rainfall characteristic usage. Meanwhile, continuous flow result of daily ground and PERSIANN-CCS satellite rainfall usage performed unacceptable for Gajahwong basin, except Code basin which showed acceptable result by using daily ground rainfall based on statistical indicators (NSE, RSR and PBIAS).

Kata Kunci : flood hydrograph, continuous flow, ModClark, PERSIANN-CCS satellite rainfall