## 3 Data and Methodology
### Economic Damage Estimation Model  
HAZUS-MH (multihazard) is widely used GIS-based software created by FEMA (Federal Emergency Management Agency) to evaluate the impact of disasters in urban and rural areas [13]. Government planners, GIS experts, and emergency management personnel use HAZUS-MH to determine losses and use the most favorable mitigation methods to minimize losses [40; 41; 42]. Accurate loss estimation gives timely emergency preparedness and disaster mitigation measures when a disaster occurs and provides a theoretical basis for subsequent recovery plans and government decisions. This study used the equations in HAZUS to estimate the damage caused by the flood to the WWTP. The damage caused by flooding is represented by the flood depth vs. damage curves. The total economic loss was later calculated by following Equation (8) [13]:  
\[\text{($\$\text{Loss}$)}=\text{($\%$ Damage)}\times\text{(Inventory $\$\text{Value}$)} \tag{8}\]  
The damage functions are presented in Table 2.  
Once the expected degree of damage was known in percentage (%), it was multiplied by the replacement value to determine the amount of damage. The replacement value in HAZUS depends on the size of the WWTP. The size of the WWTP was defined by the design capability. The definition of plant size and replacement values are shown in Table 2. The probable economic damage termed as HAZUS valuation for each size of WWTP is also shown in Table 1. Based on the design capacity of 14 WWTPs in NYC, combined with this information provided by HAZUS, Table 3 was derived. Table 3 describes the economic damage for each of the WWTPs according to the damage estimation model from HAZUS. The depth-damage functions were later utilized to quantify the economic damage sustained by the WWTPs in USD.  
After obtaining the inundation map of storm surge, high-intensity rainfall, and sea level rise, the submerged length of buildings in the WWTP was obtained through the measurement tool in GIS. The percentage of the submerged length in the perimeter of the entire WWTP and the amount of damage determined by the maximum submerged depth are essential bases for the definition of a WWTP in this study. Additionally, for this study's purpose, FEMA provided the data sets of Hurricane Sandy, which were retrieved from FEMA. For Hurricane Sandy, these data sets were in raster format, created by combining field-verified high-water marks and storm surge sensor data from the USGS. HWM (high water mark) and surge sensor data were used to interpolate the water surface elevation, and subtract it from the DEM [6].  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**WWTPs**} & \multirow{2}{*}{**Capacity**} & \multicolumn{8}{c}{**Damage (\%) by Depth of Flooding (in Feet)**} & \multicolumn{8}{c}{**HAZUS Valuation**} \\ \cline{3-13}  & & **0** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** & **(in Thousands of USD)** \\ \hline Small WWTP & \textless{}50 & 0 & 5 & 8 & 10 & 17 & 24 & 30 & 30 & 30 & 30 & 40 & 60,000 \\ Medium WWTP & 20–200 & 0 & 5 & 8 & 10 & 17 & 24 & 30 & 30 & 30 & 30 & 40 & 200,000 \\ Large WWTP & \textgreater{}200 & 0 & 5 & 8 & 10 & 17 & 24 & 30 & 30 & 30 & 30 & 40 & 720,000 \\ \hline \hline \end{tabular}
\end{table}
Table 2: WWTPs classification, damage function, and economic valuation.