The present study analyzes the spatial temporal variation of maximum flow in Slănic Teleajen and Prahova river basins (upper basin). Maximum flow rates were analyzed in relation to the threshold values corresponding to the Defence Levels respectively the maximum flow which determines exceeding Warning and Flooding Levels. The series of major floods events, selected on the basis of the threshold values mentioned above, were then statistically analyzed to determine trends (Mann-Kendall test) and the variations in the level of frequency, analysis which was applied seasonally and annually. The analysis made revealed that trends in terms of maximum flow rates in the Prahova upper basin were generally negative (decreasing), statistically significant for the February, May, July, August and the annual average, while in Slanic river basin, the trend was mostly positive, statistically significant for October.