*Flood Risk Assessment in Urban Areas: The Historic City Centre of Aveiro as a Case Study DOI: http://dx.doi.org/10.5772/intechopen.109867*

appropriate the development of a comparison between similar case studies. The example selected is the Historic City Center of Guimarães, a UNESCO Heritage Site located in the northern region of Portugal (**Figure 14a**). The case study presented is of particular relevance as it was chosen by Ferreira and Santos in 2020 as a pilot case [21], encompassing 9 blocks with 116 buildings, to implement the same methodology adopted in the present work. The area taken into consideration for the flood risk assessment is located in the "buffer zone" of the declared World Heritage Site area, as shown in **Figure 14b**.

According to Miranda and Ferreira [1], the city of Guimarães has been subjected to strong anthropogenic pressure due to increasing urban and industrial occupation, which originated the current environmental degradation of the Couros river basin as well as the substantial rise in severity of its flooding events. Hereafter, the Historic City Center of Aveiro and Historic City Center of Guimarães case studies will be addressed respectively as "Case A" and "Case B".

For what concerns the exposure and sensitivity components, the comparison between the two case studies is shown in **Figures 15** and **16**. The main difference lies in the exposure component. Case A shows a sharp distinction in the distribution of the classes in comparison to Case B, where the values are more homogeneously arranged. This depends on the wall orientation indicator and reflects the canals' location within the area. The sensitivity, on the other hand, presents a relatively uniform distribution for both cases, never exceeding the range of 40–70, approximately.

Furthermore, the overall flood vulnerability maps are shown for both case studies in **Figure 17**. The range of values for the vulnerability index in Case A never exceeds the 60–70 band, slightly higher than that in Case B, where the maximum registered values range from 50 to 60. However, the main difference lies in the percentage of buildings with recorded vulnerability higher than 30. The quantity is considerably

**Figure 14.** *The Historic City Centre of Guimarães (a) and identification of the study area (b) [7].*

**Figure 15.**

*Comparison between exposure components of Case A (a) and Case B (b) [21].*

**Figure 16.** *Comparison between sensitivity components of Case A (a) and Case B (b) [21].*

**Figure 17.** *Comparison between flood vulnerability of Case A (a) and Case B (b) [21].*

greater in Case B, reaching 40% of the 116 evaluated buildings, compared to Case A where the most vulnerable ones only represent 22% of the study area.

As seen, this discrepancy depends on the exposure component: in both cases, the most exposed buildings are also the most vulnerable ones. Even though in Aveiro there appears to be a great number of buildings presenting a higher exposure to the

*Flood Risk Assessment in Urban Areas: The Historic City Centre of Aveiro as a Case Study DOI: http://dx.doi.org/10.5772/intechopen.109867*

water flow, also considering that the canals almost completely surround the analyzed building stock, in Guimarães the Couros river basin passes through the investigated area. As a consequence, because several of the most sensitive buildings are also located in the central part of the study area, which has a great proximity to the water flow, the final values of vulnerability greatly increase. On the contrary, in Aveiro, the most sensitive buildings are not directly facing the canals.

Hence, it is possible to conclude that when applying the flood vulnerability index to a desired case study, the exposure is indeed a fundamental factor in determining the final flood vulnerability results, but so is the matching cross analysis with the sensitivity component.
