Perumusan Empiris Waktu Konsentrasi (Tc) Berdasarkan Karakteristik Morfometri Daerah Aliran Sungai

Ansori, Mohamad Bagus (2025) Perumusan Empiris Waktu Konsentrasi (Tc) Berdasarkan Karakteristik Morfometri Daerah Aliran Sungai. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Analisis hidrologi sangat berperan penting dalam pengelolaan dan pengembangan sumber daya air yang melibatkan proses transformasi hujan-debit, penelusuran banjir, desain banjir rancangan, dan lain-lain. Salah satu parameter yang dibutuhkan dalam transformasi hujan-debit dan perhitungan debit rencana adalah waktu konsentrasi (Tc). Di Indonesia penggunaan beberapa perumusan waktu konsentrasi (Tc) diatur dalam SNI 2415:2016 tentang tata cara perhitungan debit banjir rencana. Informasi mengenai debit rencana ini sangat penting terkait dengan dimensi bangunan yang akan dibangun yang berimplikasi pada tingkat keandalan bangunan, biaya pembangunan dan tingkat kerugian yang ditimbulkan dari perencanaan infrastruktur karena sebanyak 75% dari total kesalahan dalam perkiraan debit puncak dapat dihasilkan dari kesalahan dalam estimasi Tc dan menunjukkan pentingnya Tc dalam analisis hidrologi. Model perumusan waktu konsentrasi (Tc) yang akan dikembangkan adalah dengan mempertimbangkan karakteristik morfometri DAS. Formulasi dari waktu konsentrasi akan dilakukan dengan pemodelan numerik menggunakan HEC-RAS 2D versi 6.4 yang dapat memodelkan presipitasi. Alat Simulator curah hujan untuk eksperimen laboratorium digunakan sebagai validator/kalibrasi kinerja hidrologis dalam model fisik penentuan waktu konsentrasi pada penelitian ini. Penelitian ini merumuskan persamaan waktu konsentrasi (Tc) berdasarkan parameter morfometri, khususnya dengan penambahan pengaruh kerapatan jaringan drainase (D). Melalui trial and error dan pemodelan HEC-RAS 2D menggunakan metode Diffusion Wave Equation (DWE) rumus persamaan waktu konsentrasi diperoleh dengan modifikasi persaaan Kerby-Hathaway dengan Tc = 1.95. n.L)^0.467/(D^0.1.s^0.235). Validasi menggunakan 35 data model numerik menunjukkan nilai RMSE sebesar 12.65, NSE 0.84, dan PBIAS 5.91, yang mengindikasikan kinerja model yang sangat baik dalam memprediksi waktu konsentrasi (Tc). Verifikasi terhadap empat DAS terukur (Bangga, Baholomeo, Ciliwung Hulu, dan Wiroko) menunjukkan galat terkecil rata-rata 13.48%, lebih baik dibandingkan dengan persamaan Kerby Hathaway, Kirpich, dan HSS Nakayasu, yang masing-masing memiliki galat 18.70%, 27%, dan 20.37%. Hasil ini menunjukkan bahwa persamaan yang disusun memiliki kinerja yang baik dalam memprediksi waktu konsentrasi pada DAS yang diuji.
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Hydrology analysis plays an essential role in water resources management, development, and design involving the transformation process in the rainfall-runoff model, flood routing, flood design, etc. One of the needed important parameters in the rainfall-runoff transformation and the calculation of the peak discharge is the time of concentration (Tc) parameter. In Indonesia, several formulations of Tc are regulated in SNI 2415:2016 regarding the procedure of flood discharge calculation and design. The information of flood design analysis becomes very important related to the dimensions of the water structure which have an implication for building reliability, construction costs, and the risk arising from infrastructure planning because as much as 75% of the total errors in peak discharge estimations can result from the errors of Tc and exhibit the importance of Tc in hydrological analysis. The time of concentration (Tc) formulation model in this study will be developed by considering the morphometry characteristics of the watershed especially related to the drainage density of the watershed. The development time of concentration formula will be conducted by numerical modeling using HEC-RAS 2D 6.4 version which is able to model the precipitation and infiltration data. A rainfall simulator for laboratory experiments then is used to test the hydrological performance in the physical model to calibrate the time of concentration in this study. This research produces a concentration time (Tc) equation based on morphometric parameters, specifically with the addition of the influence of drainage network density (D). Through trial and error and HEC-RAS 2D modeling using the Diffusion Wave Equation (DWE) method, the resulting time of concentration equation was obtained by modifying the Kerby-Hathaway equation with Tc = 1.95. (n.L)^0.467/(D^0.1.s^0.235). Validation using 35 numerical models data shows an RMSE value of 12.65, NSE of 0.84, and PBIAS of 5.91, indicating excellent model performance in predicting concentration time (Tc). The verification formula in four measured watersheds (Bangga, Baholomeo, Upper Ciliwung, and Wiroko) shows an average minimum error of 13.48%, which is better than the Kerby-Hathaway, Kirpich, and Nakayasu SUH equations, with errors of 18.70%, 27%, and 20.37%, respectively. These results demonstrate that the developed equation performs well in predicting concentration time in the tested watersheds.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Time of concentration (Tc), HEC-RAS 2D Hydrodynamics, rainfall simulator, morphometry, drainage density,Waktu konsentrasi (Tc), alat simulator hujan, morfometri, kerapatan jaringan drainase.
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels T Technology > TC Hydraulic engineering. Ocean engineering > TC530 Flood control T Technology > TD Environmental technology. Sanitary engineering > TD171.75 Climate change mitigation
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22001-(S3) PhD Thesis
Depositing User:	Mohamad Bagus Ansori
Date Deposited:	24 Jan 2025 03:54
Last Modified:	24 Jan 2025 03:54
URI:	http://repository.its.ac.id/id/eprint/116781

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