# Evaluation of Different Simulation Methods for Analyzing Flood Scenarios in the Danube Delta
## 4 Results
The floodplain attributes were provided by the topography of the high-resolution DTM. Thus, through the HEC-RAS 1D/2D hydraulic model, the 2D flow area was generated in the study area and upstream, by designing polygons along the length of the river, including the analyzed settlements and by defining the boundaries. By defining these boundaries, the program was able to calculate the spread of the flood wave. The design of the polygons was made taking into account the scenario in which the dyke of the settlements is breached with an opening of 20 m maintained for one day. Figures 8 and 9 show the breaches induced in the dyke of the targeted settlements. Reliable historical information is not available about the positions where dam breaching occurs. From this perspective, the locations assumed for dam breaching were established considering the most vulnerable dam zones. Figure 7: Profile S3 created with the ADCP-profile trajectory, measured parameters (total flow, boat speed, average speed, measured distance, depth) and water velocity graph (velocities distributed on cells, with a colour gradient of velocity intensity, on the water column). The profile was extracted from the River Surveyor Live software (Version 4.1, SONTEK Company, San Diego, CA, USA, 2018) used in the processing of data collected by ADCP. study, the energy slope was approximated by using the average slope of the water surface near the cross-sections. The next stage defined the start and end period of the simulation. Several flow hydrographs were applied in the software, corresponding to the flood stages, to obtain several flood scenarios (32 scenarios in total). The flood stages are presented in Table 4.  
For each settlement, four flooding stages were applied with intervals between 60 cm and 62 cm (Partizani settlement), 17, 40, and 80 cm (Ilganii de sus), 16 and 60 cm (Vulturu), 38 and 40 cm (Maliuc), 20 and 21 cm (Gorgova), 15 and 40 cm (Mila 23), 20 cm (Crisan), and 9 and 20 cm (Sulina). Flooding stages were presented in the Sulina Black Sea reference system and the Black Sea 75 system. Flooding stages were calculated from the lowest flooding level to the highest flooding level for each analyzed settlement. Thus, different flood scenarios of the settlements for different water levels in the river next to them could be visualized. In the software, the hydraulic calculations were performed on 06 July 2010 at 10:00, for 24 h (the timeframe in which the flooding breach is maintained in the dyke for the dynamic method). Thus, 32 scenarios were run by execution of the unsteady flow simulator, the pre-processor geometry, and the output post-processor, finally obtaining the results by the first method (dynamic). The process of hydraulic modeling involves the introduction and use of a large number of data, both geographical and hydraulic [36]. After completing the data entry process and validating the model (including resolving the data entry errors), the program was run and the results of the hydraulic modeling were obtained. The results of hydraulic modeling can be visualized in several ways: maps, graphs, or tables. In the present study the results were displayed in the form of the flooding maps. For the static method Global Mapper v17.0.2 specialized software was used. Less data were processed with this method than with the previous one. Geographic data, regional boundaries, and orthophotomaps were processed, but mostly the high-resolution digital terrain model. For the correct processing of the information, and to select the study area, the digital terrain model was introduced into the software, and translated into the suitable reference system (STEREO 70, EPSG: 31,700 with the Black Sea 75 system for elevation points). The next step was the individual clipping of the area of interest from the digital terrain model (a sufficiently extensive perimeter was chosen to perform the simulation; this perimeter covered the administrative territorial unit and the adjacent territory for each settlement).