## 4 Results and Discussions
Thus, between simulations 2 and 3, there is a sharp decrease in erosion power of about 50%. The decrease in the erosive power with approximately the same value is also observed between simulations 3 and 4, at the same time noticing an increase in the erosive power within simulation 4 in the immediate upstream vicinity of the dam. This fact introduces instability in the proposed hydro-ameliorative assembly (Figure 16). Regarding the changes that occurred at the level of the analysed indicator (stream power) in the sector upstream of the dam, they have similar trends of variation. Significant changes are identified only in the immediate vicinity of the dam proposed into the simulation. The general trend is to decrease erosion due to the accumulation of water volumes behind the dam and at the same time the decrease in forces acting on the ravine. The models for simulating the behaviour to external destabilizing factors of territorial systems are necessary in order to make the best decision based on the analysis of the results obtained from the simulation [48; 49]. In the present study, based on the results analysis of the three simulations, it was decided that the implementation of hydro-amelioration work in simulation 3 is the best implementable technical solution for introducing a relative stability in the analysed system. The choice is based on the main advantage over the first simulation, respectively, that the erosion of the banks of the perimeter of the proposed work is 0 and the volume of water at maximum flow does not exceed the maximum elevation of the dam. The fact that the maximum volume exceeds the maximum elevation of the dam introduces instability in terms of the structure proposed in simulation 2 by lateral erosion and exposure of the embankments of the dam, as well as by exposure to regressive erosion at its base. Due to the introduction of the overflow as an additional element and at the same time raising the elevation of the dam in simulation 3, the volume of water recorded at maximum flow will be discharged through the overflow, thus reducing lateral erosion and shear stress, both at the base of the dam and at the lateral extremities. In the case of simulation 4, an additional element is introduced, namely the evacuation pipe, which, theoretically, should add value to the proposed hydro-amelioration work by reducing the volume of water recorded at maximum flow and reducing the shear stress value. The shear stress is diminished because in the immediate vicinity of the dam, in the upstream sector an erosion channel is formed, which is directed towards the exhaust pipe favouring bottom erosion and directing the transport vectors of suspended alluvium to the proposed evacuation. This will lead in time to the clogging of the pipe with eroded material, requiring frequent and complex maintenance works, due to the long length of the pipe, which leads to additional costs that should be avoided in these categories of works. Another weakness regarding the implementation of the hydro-amelioration work proposed in simulation 4 is the fact that additional technical excavation works are needed to bury the pipeline works that require intervention in the ravine system, leading to changes in its morphometry and morphology. These additional earthworks could lead to the destabilization of the whole system and the emergence of related erosion processes in the downstream sectors. The decision to implement the hydro-amelioration work included in simulation 3 is supported by the comparative analysis of all implemented simulations, being the most viable in terms of implementation-operation costs, as well as in terms of ameliorating impact on the studied ravine [50; 51; 52]. The complex arrangement of the analysed ravines involves the establishment of two more hydro-improvement dams: one downstream of the receiving basin of the torrent to control in terms of erosional power Sector II of the ravine, and one in hotspot 3 to significantly reduce its development from a spatial point of view.