## 5 Discussion  
The main feature of this study was that the WWTPs could be considered as a building rather than a point. To further compare the difference between the inundation maps obtained by considering WWTPs as buildings and points, this study also used the same data source, taking the WWTP as a point on the map to obtain the inundation maps of 14 WWTPs in NYC. Taking the storm surge as an example, Table 8 shows the flood depth obtained from the inundation map of a SLOSH category 2 hurricane when the WWTP is regarded as a point and a building. Research conducted by McAllister also reported a similar surge level at King's Point on Long Island and at Battery Park in Lower Manhattan [47]. In the flood analysis of the WWTP, the storm surge inundation map obtained by treating the WWTP as a point does not fully show the inundation status of the \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**WWTP**} & **Total Flood** & **Rainfall** & **Sea Level Rise** & **Strom Surge** \\  & **Depth/ft** & **100 yr/ft** & **1 ft/ft** & **CI/ft** \\ \hline Port Richmond & 13.96 & 6.89 & 0 & 7.07 \\ Oakwood Beach & 1.54 & 0 & 0 & 1.54 \\ Tallman Island & 0.46 & 0 & 0 & 0.46 \\ Rockaway & 2.33 & 0 & 0 & 2.33 \\ Jamaica & 0 & 0 & 0 & 0 \\ Bowery Bay & 0.24 & 0 & 0 & 0.24 \\ Hunts Point & 0.35 & 0 & 0 & 0.35 \\ Red Hook & 4.62 & 0 & 0 & 4.62 \\ Owls Head & 1.42 & 0 & 0 & 1.42 \\ Newtown Creek & 4.06 & 0.33 & 0 & 3.73 \\ Coney Island & 0 & 0 & 0 & 0 \\
26 th Ward & 1.83 & 0 & 0 & 1.83 \\ North River & 2.92 & 0 & 0 & 2.92 \\ Wards Island & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Estimation of the potential magnitude of flood depth due to the compounded effect of high-intensity rainfall, sea level rise, and storm surge. WWTP. In addition to the inability to show which areas of the WWTP are submerged, it is also unable to have deviations in the flood depth. Similar flood depth was also found by [PERSON] et al., which showed a flood depth of 1.98 m (6.49 ft) for Hunts Point WWTP [44]. Research conducted by McAllister also reported that the flood elevations for the affected WWTP during hurricane Sandy exceeded the flood depth outlined by FEMA flood maps, and the 100 year flood elevation [47]. As shown in Table 8, the flood depth obtained when the WWTP is regarded as a point has only one value, mostly between the maximum and minimum flood depths obtained when the WWTP is regarded as a building. A study conducted by [PERSON] et al. also pointed out major damage for the WWTP infrastructures with the WWTP with Coney Island being damaged the most [43]. However, there are exceptions, such as the Newtown Creek WWTP. When the WWTP is regarded as a point, it was shown that it had not encountered floods, but in fact, the maximum flood depth of the Newtown Creek WWTP was 9.65 ft, the minimum flood depth is 2.90 ft, and the percentage of submerged length is 92.13%. The Bowery Bay WWTP, North River WWTP, and Wards Island WWTP also have the same problem. In addition, the division of NYC into 889 sub-basins also has apparent advantages in calculating runoff. NYC covers a very large area. When it encounters unevenly distributed rainfall, if the entire NYC is used to calculate the runoff, the accuracy of the resulting flood maps and data is reduced. In this study, a 20 min rainfall event with an average rainfall intensity of 10.9 cm/h was used as an example to compare the inundation maps and data obtained by dividing NYC into sub-basins and not dividing it into sub-basins. Taking the Newtown Creek WWTP as an example, Table 9 shows the difference in flood elevation and flood depth obtained by dividing and not dividing sub-basins when calculating runoff.