The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development (Part II)

This paper is the second part of a comprehensive two-part series on the ITB Unit Hydrograph (ITB-UH) Method, titled The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development. Building on the foundational concepts introduced in Part I, this paper delves into advanced applications of the ITB-UH Method, emphasizing its adaptability, calibration capabilities, and real-world utility. The ITB-UH Method introduces novel derivations for the Peak Rate Factor (Kp) and Peak Discharge (Qp), along with a time-step normalization approach that enables flexible adjustments to unit rainfall durations and a systematic calibration process. These innovations significantly enhance the method’s versatility and accuracy in modeling flood discharge across diverse hydrological conditions. The practical applicability of the ITB-UH Method is demonstrated through real-world flood discharge calculations in the Pinamula River, located in Buol District, Central Sulawesi Province. Three illustrative examples highlight the method’s versatility: (1) analyzing flood hydrographs at a 1-hour time step to showcase its practical applicability for flood management; (2) recalculating flood hydrographs with a finer 0.5-hour time step to demonstrate its adaptability to varying temporal resolutions; and (3) refining model parameters to improve alignment with observed flood hydrographs, underscoring the method’s capacity for calibration and optimization. To evaluate the method’s performance, robust metrics such as the Nash–Sutcliffe Efficiency (NSE), Percentage Bias (PBIAS), and Index of Agreement (IA) are employed. These metrics confirm the ITB-UH Method’s accuracy and reliability, with results consistently aligning closely with observed data. Collectively, the findings underscore the ITB-UH Method’s suitability across diverse hydrological settings and its potential to enhance both the verification of existing SUH methods and the development of user-defined hydrographs. By enabling more accurate and effective flood management, the ITB-UH method represents a significant advancement in hydrological modeling, with broad implications for water resource management and infrastructure planning worldwide. Doi: 10.28991/CEJ-2025-011-05-015 Full Text: PDF