# Delineation of the Flooded Areas in Urban Environments Based on a Simplified Approach
## 4 Results  
The simulations were performed at the level of each sub-basin, and the results are presented both at the local level (meaning sub-basins) and globally at the level of the four main urban basins (BH1,..., BH4). In the following, only the results obtained for BH3, which has the largest area (2.76 km\({}^{2}\)), are provided. In this urban basin, there is an important number of areas flooded by torrential rainfall, namely the Objects 2, 3, 4, 5, and 6 (Babadag, Victoriei, Unirii, Pacii streets and Parcul Carol). The urban basin BH3 contains a large number of sub-basins, marked by hatches in Figure 16.  
It should be mentioned that in addition to the hatched surfaces from the previous figure, due to the street plot, water originating from some neighbouring basins is accumulated in the area of the five objects. The surfaces that generate an additional flow are shown in Figure 17.  
The water fluxes from the left side of the image are directed towards Object 3 (Victoriei street). The flows from the right side are directed towards Pacii Street (Object 6), and from here accumulate in the Delta hotel roundabout and in the Carol Park areas. The calibration was made considering the 12-13 September 2013 rainfall event. The flood hydrograph in Hypothesis 1 (the sewage system is 100% non-functional) at the most downstream section (Figure 18) represents the contribution of all upstream sub-basins, including flood composition and propagation. The maximum discharge simulated for the 2013 event in Hypothesis 1 is 26.8 m\({}^{3}\)/s, while the accumulated volume in depression areas is 132,400 m\({}^{3}\). Figure 16: Sub-basins located in the area of Objects 2, 3, 4, 5, and 6. Figure 17: Additional surfaces that discharge in the area of objects 2, 3, 4, 5, and 6. Figure 18: Simulated flood hydrograph in Hypothesis 1 for the 12–13 September 2013 event: (**a**) discharges and (**b**) flood volume. In Hypothesis 2 (designed capacity of the corresponding sewage branch is 6.47 m\({}^{3}\)/s), the maximum discharge simulated for the 2013 event was 20.3 m\({}^{3}\)/s, while the accumulated volume in depression areas was 33,660 m\({}^{3}\). The modelled extension of the flooded areas for the 12-13 September 2013 event (for the two hypotheses, with regard to the functionality of the sewage system) is presented in Figure 19. The actual extension of the flooded area at the 2013 event is closer to the situation modelled in Hypothesis 1, which shows that the sewage system did not work at its designed capacity. Similar results were obtained for the 14 June 2016 rainfall event. In Hypothesis 1, the simulated maximum discharge was 11 m\({}^{3}\)/s and the volume was 42,835 m\({}^{3}\), while in Hypothesis 2 the corresponding values were 4.57 m\({}^{3}\)/s and 9350 m\({}^{3}\), respectively. The extensions of the flooded areas are presented in Figure 20.  
In Hypothesis 2, the flooded area is much smaller than in Hypothesis 1, with a relatively large water accumulation in the area of Unirii Street. Compared to the flooded areas during the 2016 event, the results corresponding to Hypothesis 2 did not match the  
Figure 19: The flooded areas derived for the 2013 event: (**a**) Hypothesis 1 and (**b**) Hypothesis 2. Figure 20: The flooded areas derived for the 2016 event: (**a**) Hypothesis 1 and (**b**) Hypothesis 2.  
actual flooded area, suggesting again that the sewage system was not fully operational. The grate inlets were probably blocked by floating debris, and the collectors partially clogged. Following the calibration and validation stage, simulations for design storm corresponding to the frequencies 1:2; 1:5; 1:10; and 1:100 were performed in both hypotheses of functionality of the sewage system: (a) Hypothesis 1, 100% non-operational and (b) Hypothesis 2, fully functional. The duration of precipitation was 40 min, and the precipitation structure corresponded to the event of September 2013. The AMC-III condition was used in the simulations.