Abstract: The present study approaches a series of geomorphological aspects specific to hydrographic basins of small sizes which, in certain circumstances, favor the occurrence of floods having major effects upon the human settlements. We focused our attention on three neighboring hydrographical basins, located in a mountainous area in the north of the Romanian Carpathians, where on the 24th of July 2008, following some heavy rains, there occurred major floods. Although the three rivulets the Valea Seacă, the Izvorul Alb and the Valea Caselor are tributaries on the right side of the Moldova river, the behaved differently during the above mentioned flood. The particularity is that within the Izvorul Alb hydrographic basin the maximum flow during the flood was two time lower than in the case of the other two basins between which it is located. Given the fact that the quantity of precipitations received by all three basins did not differ and the physical-geographical features are similar, there was performed the morphometric analysis of all three hydrographical basins in order to outline the morphometric variables with a role in the concentration of the runoff: the surface, the slope, the roundness, the shape coefficient, etc. The conclusion drawn from this case study is that the asymmetry of the basin is an essential parameter in making the difference in respect to the behavior of small hydrographical basins during the formation of exceptional floods.