Analysis of Recorded Rainfall Information for the Purpose of Huff Curves Extraction in the Dez Dam

Identifying the rainfall characteristics and understanding the rainfall-related processes is one of the key factors in the scientific management of water resources. Selection of the design storm is the first step in the estimation of the design flood. Determining temporal rainfall patterns is very important as one of the design rainfall properties in flood estimation and the design of drainage systems. This study was concerned with the pattern of rainfall depth during its occurrence at the Dez dam station. In order to plot Huff curves in the Dez dam station, the recorded data of the rain gauge was used. For this purpose, all 280 storms from 1972 to 2016 in different seasons were classified into the five distinct classes including i) 0-2 hours, ii) 2-6 hours, iii) 6-12 hours, iv) 12-24 hours, and v) more than 24 hours. Furthermore, for each class and in each of the seasons, the Huff curves were plotted using all storms information single class. Moreover, for the considered station, all recorded events were considered in a single class and the general Huff curve was plotted using the probability of 50%. In general, the highest number of storms in the Dez dam (about 32.9%) was grouped in the second quartile. However, it was about 55, 48.5 and 50.4 percent in the case of short storms (0-2 hours) for spring, autumn and winter, respectively. In contrast, low percentages were obtained for the rainfalls having long durations. The Logistic equation was extracted for all Huff curves. These curves would be useful in efficient water resources management. The value of the correlation coefficient between the amounts obtained from the Logistic model and the corresponding values extracted from the curves was more than 0.99, which was significant in 1 percent.