Author(s): Mofid Gorji; Seyed Khallagh Mirnia; Mashad Gholi Maramaei
Linked Author(s):
Keywords: Natural unit hydrograph; “Gray” and “FSR” synthetic unit hydrographs; Kasilian catchment
Abstract: Synthetic Unit Hydrograph (SUH) is a deterministic method to estimate maximum flood discharge for ungauged points on the stream where the runoff data are not available. The exactness of this method depends upon the type of SUH and the catchment characteristics. Since the accuracy of Gray and Flood Studies Report (FSR) SUHs has not been evaluated so far in Iran, the Kasilian representative catchment in the north of Iran was considered to accomplish this work. In this study, twelve events of rainfall-runoff in non-melting seasons were chosen and their rainfall hyetographs and flood hydrographs were gathered from two automatic recording stations. Then, the Natural Unit Hydrographs (NUHs) were determined by least square method. A comparison study between the index NUH with obtained Gray and FSR SUHs was undertaken. The results showed that; i) in Gray method, the difference of synthetic values with observed values, based on 1-hour excess rainfall, is+15.02, -15.5 and+21.79 percent in time to peak, time base and peak discharge, respectively. and ii) in FSR method the difference is–12.01, +21.21 and–47.14 percent in time to peak, peak discharge and time base, respectively. Evaluation of the results showed an acceptable accuracy of both methods in Kasilian catchment, depending upon the aim of the research, especially after calibration process.
Year: 2002