Comparison of different methods of peak flood discharge estimation in Khorasan Razavi province

Flood estimation with certain frequency is one of the fundamental factors for designing hydraulic structures، floodplain planning، river coastal stabling، and watershed management. The Kushkabad watershed is one of the main sub-basins of Kashafroud basin located in the north-east of Iran، with an area of 87. 45 km2، and 11 kilometers far from Mashhad، which has always been facing severe damages due to flash floods in special climates and topography. In this research، HEC-HMS، flood frequency analysis، Creager، Dicken and Fanning rainfall-runoff hydrological empirical methods were compared. The statistical index of relative percent error was used for comparison of different methods. The results showed that HEC-HMS model has little difference with observed data، and empirical methods have a reliable approach with HEC-HMS model. On the other hand، regional flood frequency analysis has more significant difference with reality.