## 2 Materials and Methods
### Data  
Two spatial data sets support the study: (i) Portuguese Statistics Geographical Information (Census 2021) for small territorial units (neighbourhoods). The neighbourhood is the territorial unit that identifies the smallest homogeneous area, representing a block in urban areas, and (ii) the Land Use and Land Cover (LULC), named as COS 2018 (minimum mapping unit of 1 ha), provided by the Direcao-Geral do Territorio, available on the Web Feature Services [33]. The variables are presented in Table 1, distributed according to the criteria used in the group based AHP built on the hierarchical structure. From the Census (2021) data, it was possible to characterise the population, buildings, and socio-economy. COS 2018 data were used to characterise the exposed elements. The rationale behind the choice of these variables can be found in [PERSON] et al. [29] and [PERSON] et al. [9] and were summarized here. Population variables take into account age structure, gender, and family size. Age structure was divided into three classes to allow for the classification of vulnerability by age. Children and older people are thought to be more vulnerable to flooding [34; 35; 36]. Gender is used to differentiate vulnerability between women and men. Women tend to be more risk-aware and prepared to act [35]. However, women may face more difficulties during the recovery phase, often due to their lower wages and family care responsibilities [34; 35]. The number of family members is used because larger families often have to share sources of income and have more dependents to evacuate, such as children and the elderly [34; 35; 37; 38]. Building variables include the year of construction, number of storeys, building function and use. The year of construction was divided into buildings constructed before and after 1980. In 1980, Portugal introduced safety regulations for building structures. Older neighbourhoods also have older drainage systems. These may be more flood-prone [39]. The number of storeys was divided into buildings with one or two floors and with more than three floors. [40]. People and their property can be protected when on the upper \begin{table}
\begin{tabular}{c c c c} \hline \hline
**P** & **Population** & **B** & **Buildings** \\ \hline P1 & _Age structure_ & B1 & _Building year_ \\ P11 & Percent of residents under 14 years old & B11 & Percent of constructions built before 1980 \\ P12 & Percent of residents over 65 years old & B12 & Percent of constructions built after 1980 \\ P13 & Percent of residents between 14 and 65 years old & B2 & _Floors_ \\ P2 & _Gender_ & B21 & Percent of buildings with one or two floors \\ P21 & Percent of male residents & B22 & Percent of buildings with three or more floors \\ P22 & Percent of female residents & B3 & _Function_ \\ P3 & _Family Number_ & B31 & Percent of buildings that are exclusively or mainly houses \\ P31 & Percent of households over 5 individuals & B32 & Percent of buildings that have a non-residential function \\ P32 & Percent of households under 4 individuals & B4 & Percent of buildings that are a collective accommodation \\
**S** & **Socio Economy** & E & **Exposed elements** \\ S1 & _Level of education_ & E1 & _Land use_ \\ S11 & Percent of individuals who completed junior & E11 & Percent of urban area \\ S12 & Percent of individuals who completed high school & E12 & Percent of agricultural area \\ S13 & Percent of individuals who completed university & E13 & Percent of forestry area \\ S2 & _Housing occupancy_ & E2 & _Population density (Inhab/km\({}^{2}\))_ \\ S21 & Percent of homes owned & E3 & _Building density (buildings/km\({}^{2}\))_ \\ S22 & Percent of homes rented & & \\ S3 & _Percent of unemployment rate_ & & \\ S4 & _Percent of illiteracy rate_ & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Description of the data used in the AHP-GDM. floors of buildings. Collective buildings (e.g., nursing homes, hotels, hospitals, and prisons) are more vulnerable, because they present additional difficulties in the evacuation and resettlement process.