Flood, as one of the most important natural disasters, has always been considered by human being, and in recent years the need to pay more attention to it is felt by the development of population, industrial and agricultural centers and increase of damage caused by flood. In this study, through a statistical survey and using the conventional statistical distribution in hydrology, it has been tried to estimate the magnitude and time of occurrence of flood in the watershed of Mohammad Abad in Gorgan with more accuracy. For this purpose, using the Smada software, the maximum daily flow rate in different return periods for each month was determined using appropriate statistical distribution. Estimates have shown that the appropriate statistical distribution is the Log Pearson Type 3. Floods with a return period of less than 25 years are more likely to occur in May and floods with long return periods, namely 25 to 200 years, in November. Furthermore, by determining the capacity of the Mohammad Abad River passage, it became clear that the village located at the downstream of the basin with floods with a return period of more than 25 years suffers from flood concentration and damage. Therefore, flood management plans need to receive greater consideration in these months in order to minimize the life and financial losses due to potential flood occurrences.