The increase in intensity of torrential rains of Romania over the last decades, as a consequence of the general tendency of global warming, has triggered many flash-floods especially in small and very small river basins which in turn have generated a lot of damages, from loss of human lives to important material prejudices. The paper focuses on determining the vulnerability degree of small river basins from Someş river basin regarding flash-floods in general and is composed primarily of two parts: in the first part we have presented one of the most destructive flash floods that took place in Someş river basin, on the 20-21 June 2006, in the second part we have calculated an index that estimates the vulnerability degree that small river basins from Someş river basin have when discussing the matter of flash floods.