Analysis of storms of Karkheh dam basin and extraction of design hyetographs using the Huff method

Providing design hyetograph is an important issue in accurate determination of urban drainage networks. One of the important relevant problems of floods, is its safe transmition without any damage to facilities, farms, habitat buildings and so on. This needs accurate determination of flood quantity and then dimensions of water pass ways, bridges, flash walls, culverts, and so on. The aim of this research is plotting the Huff curves and design storm hyetographs in the six selected stations in upstream of Karkheh dam watershed. In order to design of Huff curves, the recorded date of Kamiaran, Abdanan, Darreh-shahr, Kerned, and Kermanshah were used. For this purpose, the 1191 recorded storms classified in different seasons and in five classes of rainfall durations. The Huff curves were illustrated using the mentioned information for each of the classes as well as the seasons. Furthermore, all the events in a given class and season merged in a universal distinct class and then their Huff curves were plotted too. In order to possibility of comparison of temporal distribution of rainfalls in stations, three new indices denoted by S, I, and Q were defined, each of them shows the ratio of cumulative rain depths received in 25, 50 and 75 percentages of storm durations extracted from the 10 percent Huff curves to the corresponding values obtained from the 50 percent Huff curve.  Results showed that nearly in all the stations the quantity of S-index was greater than I-index, and both of them were greater than Q-index. Results of this study have practical application in surface water management in the watershed area.