بررسي نقش عوامل فيزيوگرافيك حوضه بر دبي هاي حداكثر لحظه اي در زيرحوضه هاي گرگانرود به منظور ارايه مدل منطقه اي سيلاب

Investigation of the role of physiographic factors on instantaneous peak discharges in Gorgan river sub-basins for the regional flood modeling

Estimation of an accurate peak discharge at unguaged catchments can be important when the weirs dimension calculates to reduce the flood risk to gain the purpose of engineering and economic projects. The regional model of peak flow estimation is a method that instantaneous peak flow is function of catchment area, but it is also expected that flood discharge depends on the climatic and physiographic factors such as drainage density, form factor, length of catchment, mean precipitation and etc. The purpose of this study is to find the best regional model for the peak flow estimation with return period in sub-basins of Gorgan-river catchment in Golestan Province. As an investigation technique in relation to gauge stations, 20 stations were selected which are analyzed in relation to climatic and physiographic factors. The results shown that 93.9 percent of variances of 5 selected variables which are more important than the other variables such as area, drainage density, form factor and bifurcation ratio. The catchment area and drainage density divided as homogenous region in clustering and multiple regression methods and also 5 independed variables identified for two positions in discharge estimation models on different return periods. In different ways; first of all the whole area and then homogenous region were selected for purpose of modeling. Finally it can be concluded that the recommended models for the whole region are more suitable than the other models. In models with the return periods of 2, 3, 5 and Ili years only the area factor was effective. But in the models with return periods of 25, 50 and 100 years in addition to the area, elevation of the catchment was also calculated in models which is shown the same results from the other researches.