The response of Karoun basin in Lumped and Semi-distributed simulation were compared. Also, the flood intensity of the sub-basins and the effects of physical parameters on flood hydrograph have been investigated. Results demonstrated that there was no significant difference between the characteristics of flood hydrograph in lumped and semi-distributed simulation. Also, results showed that the flood intensity of each sub-basins doesn’t just depend on the area of each sub-basin and further parameters such as the distance of each sub-basins based to the basin outlet and some other physical or climatic parameters would affect the flood intensity of each sub-basins. Based on the results of prioritizing the intensity of each sub-basins in the study area, Barez and Dazakabad sub-basins are in the first and seventh priorities based on the share of sub-basins on flood discharge. However Barez and Soulekan sub-basin ranked in first and seventh proiorities based on the share of sub-basins per unit area. Sensitivity analysis has been done based on five important parameters including; main river slope, Gravelius coefficient, curve number, area of sub-basins and the average slope of basin. Results indicated that the curve number has been the most effective factor on the flood rates of each sub-basin. Therefore, a suitable management for the land use changes as the most effective factor on curve number would greatly control the basin flood intensity.