Risk of Dynamics of the River Stream in Tectonic Areas. Case studies: Curvature Carpathian – Romania and Maghrebian Chain – Algeria
Abstract: The tectonic characteristics of the Alpine orogeny highlight some similarities in the genesis of landforms over large areas. This paper analyses the role of tectonic processes in two subsiding areas with uplift movements. The overall tectonic activity implies the formation and evolution of the hydrographic network and its correlation with the major relief structure, thus forming streams parallel to the high-altitude lines, as well as consistent, transversal, and subsequent streams.These tectonic processes are accompanied by antecedents and/or epigenesis common in the Eastern Carpathians, Romania. Hence the Bistrița River is longitudinal compared to the Bistrița and the Stânișoara Mountains, but also transversal in other sectors. In Algeria, the Northeast, especially the Zighoud Youcef zone (NE of Constantine), is characterized by a particular morphography and morphometry of the river basins which reveals reorganizations of the river network through their transversal or longitudinal characteristics compared to the structure and tectonics of the region. In areas with imminent catchments, the regressive erosion amplifies the slope dynamics and slope processes vulnerability.The uplift and subsidence movements impose reorganizations of the hydrographic network of the catchments with the alternation of the erosion and sedimentation processes it creates a certain fluvial style pattern. In the subsidence of the Întorsura Buzăului depression, the longitudinal profile of the Buzău River has a very low slope and its meanders create islets. This is subject to frequent floods which imposed the riverbed regularization. However, in Zighoud Youcef, the Oued Smendou River also indicates some similarities with the Buzău River structure due to subsiding areas of the Mila-Constantine basin.