## 1 Introduction
Three types of hydraulic and hydrodynamic models can be used for hydraulic modeling: one-dimensional (1D) [39; 40], two-dimensional (2D) [41; 42], combined (1D/2D) [43; 44] and three-dimensional (3D) [45]. For the analysis carried out in the 1% flood band of the Turcu River (Olt basin, Romania), the 1D model could be successfully used, which is easy to generate [46], process and use, but, compared to the other models, it has the disadvantage of some limitations, such as the inability to simulate lateral flood wave diffusion and vertical turbulence. The 1D hydraulic and hydrodynamic model was chosen not only because it is commonly used, but also because of its efficiency in terms of processing input data on hardware with relatively modest functional characteristics. One-dimensional modeling also remains suitable for flood simulation because it is easy to generate and use. One of the main advantages unanimously recognized is its efficiency in terms of computation time. Another main advantage is that the 1D model is suitable for use in morphologically well-defined riverbeds with relatively close, bilaterally distributed terrace heads and/or slopes where river flow and overflow do not spread significantly. Such conditions are also valid for the Turcu mountain valley, whose floodplain is clearly delimited laterally and has a width from 50 m to 450 m, approximately. At the national level (Romania), the National Administration \"Romanian Waters\" (A.N.A.R.) was implemented in the 2014 Directive 2007/60/EC. For the creation of hazard maps, a group of specialists, formed at the level of A.N.A.R. and the National Institute of Hydrology and Water Management (I.N.H.G.A. ), used the results obtained within the National Programme Plan for the Prevention, Protection and Mitigation of Flood Effects (P.P.P.D.E.I) [47; 48], based on hydraulic modeling methods and using the HEC-RAS application by constructing and exploiting the one-dimensional (1D) hydrodynamic model; the results of simplified methods for generating flood curves were applied in areas that were not covered by the P.P.P.D.E.I. This concerned watercourses not modeled in the P.P.P.D.E.I, but with relatively large catchment areas or characterized by extensive flood zones (Tarnava Mica, Teuz, etc.). It was noted that the effects of climate change were not taken into account in the modeling and analysis that were carried out [49]. Also, at a national level, for the risk maps, the degree of risk was taken into account according to water depth, establishing three classes (low risk \(<\) 0.5 m, medium risk 0.5-1.5 m and high risk \(>\) 1.5 m). However, according to the developed risk matrix [49; 50], four flood risk guards were established: 0--insignificant residual risk (agricultural and other land at the edge of settlements), 1--low risk, 2--medium risk and 3--high risk. The approach in the current research is based on the delineation of two water depth ranges (\(<\)0.5 m and \(>\)0.5 m) within the 1% flood belt and the intersection of their areas with the mapped intra-urban space for the five localities crossed by the Turcu River in the belt area, in order to delimit the risk classes: high, medium, low and residual risk. The insignificant surface of the floodplain area \(>\)1.5 m suggested the modification made to the national approach. The resulting national hazard and risk maps [51] were developed for three flooding scenarios, low, medium and high probability, for peak flows with a probability of the exceedance of 0.1%, 1% and 10% having a corresponding statistical return period once every 1000, 100 and 10 years. For the same maps, the hydraulic modeling to define the 1% floodplain of the Turcu River was based on the value of the maximum flow with 1% exceedance probability, Q1% = 230 m\({}^{3}\)/s, recorded at the hydrometric station (SH) of Tohanu Nou (Brasov county) [52]. Measured at the same station, the value of the historical maximum flow Q of 120 m\({}^{3}\)/s, recorded on 2 July 1975, is also known.