Maryam zolfaghari - PhD student in watershed management, Science & Research Branch Islamic Azad University.Tehran
Mohammad mahdavi - PhD in Hydrology, Faculty of Natural Resources, University of Tehran
Mohammad Reza Ghanbarpour - PhD in water recourses management Faculty of Natural Resources, University of Mazandaran
Mahmood Habibnezhad - PhD in Hydrology, Faculty of Natural Resources, University of Mazandaran

Nowadays, flood is one of the most impliticated events that endangers human life and wealth more than any other natural disaster (1).Science flood has always caused many problems in most parts of the world.invetigation of different time parameters in flood hydrographs of the same regions makes hydrologists able to simulate it in order to plan for flood destructive effects decrease. these time parameters are such as peak, lag and concentration time. there are some formula for lag time estimation as a variable depending on flood rate in each catchment(10).it is possible to study maximum flood discharge, flood bollume and the rate of catchment storage by investigating observed hydrograph of catchment. It also has an important role in planning the dimension of water works. In fact making use of hydrographs and determining concentration ,lag and peak times is one of the main and key required parameters in hydrologic analysis(13).It is essential to estimate time parameters such as peak time and also peak discharge to prevent flood and its risks(12).using hydrograph and the corresponding hyetograph observed events analysis is one of the important methods in determining time parameters of hydrograph(2) which are mostly used in spillway dimension and flood routing .The estimation of fazelabro channels dimension and determining the dimensions of flood control works. If there is any error in concentration time estimation, It causes problems in flood design and also 75 percent (75%) error in maximum discharge (7,8).

Flood Hydrograph, timse parameter, Empirical methods, neka,karaj,kasilian