Volume XI |

Torrentiality – Morphohydrographical conditions in the Sebeş Basin (The Parâng Mountains Group, Southern Carpathians)

Abstract: This paper presents the morpho-hydrographical characteristics that define the torrential system inside the Sebeş basin (the Parâng Mountains). The manifestation of torrential erosion takes place on river basins of different sizes. In order to bring out the quantitative and qualitative differences in the stream discharge structure, we resorted to the determination of some geomorphometrical indices such as: the number of river segments, the frequency of elementary thalwegs, incipient or total torrentiality. The great density of the temporary valleys network, along with the emphasized slope of the ditches and flanks generate a high instability. The local differentiations of the geological sublayers and the complementarity of the use of the Cindrel, Lotru and Şureanu mountain areas generate its own answer forms on the aggressive action of the torrential rainfalls on elementary segments with temporary functionality, as well as on permanent hydrographic thoroughfares. The tributary streams received by the Sebeş River in the Carpathian sector have small hydrographic basins and they do not exceed rank 4 in the Horton-Strahler classification system. Torrentiality is stimulated by the combined effect of snowmelt and spring rains, but mostly by the aggressiveness of the torrential summer rains, which take over a modified geomorphological background through excessive depasturage, deforestation and hydropower harnessing. The streams and the floods, through the accumulation of high volumes and energies, produce slope damages, riverbed shifts, blockages and the destruction of communications infrastructure, and material loss.