**3. Case study: the Historic City Centre of Aveiro**

The city of Aveiro is located on the shore of the Atlantic Ocean, in the Central region of Portugal. The territory is administratively designated as Beira Litoral, with Aveiro being the capital of the district and the name of the municipality (**Figure 2a**). The city has a population of 80,880 and a total area of 197.58 km<sup>2</sup> .

The city's location (**Figure 2b**) has unique characteristics: while to the east it is confined by mountains, to the north, south, and west spreads the immense lagoon to which the city gives its name—Ria de Aveiro—and that distinguishes the surrounding scenery stretching out to the sea. In an area geographically and historically isolated from the mainland communication routes, the estuary of the numerous waterways that flow into it has, over the centuries, been the determining factor in the movement

**Figure 2.** *Aveiro's city centre (a) and entrance of the Barra da Ria de Aveiro (b). Sources: Getty images/Google Earth.*

of people and goods. In particular, the river Vouga, the largest of the watercourses, presents an important communication route. The existence of the Ria de Aveiro is essentially linked to the one of the city. Today, it is composed of countless islands, lagoons, and channels; however, throughout the centuries, the natural substrate has undergone profound changes, which has eventually led to the formation of the estuary.

### **3.1 History and development of Aveiro**

Nowadays, Aveiro is one of the most populated cities in Central Portugal, grown around its thriving port. Nevertheless, over the centuries, the process of consolidation and growth of Aveiro has gone through different phases, each reflecting the living conditions in the region and its relationship with the lagoon and the sea.

Initially known as *Avarium*, documentation seems to place the origin of the city at least back to the 10th century. The first centuries of Aveiro's existence are essentially marked by a period of consolidation of the primitive village, developed around the main church of St. Miguel, which assumed the status of a city only in the 13th century. Always linked to economic activities, Aveiro invested in the salt production and in the naval commerce as its most valuable assets, which constituted the main economic activities that accompanied its growth until the end of the 14th century [16].

Following the centuries, the building of the walls around the urban center and the development of the salt industry, agriculture, and fishing established for Aveiro a period of prosperity. However, the sedimentation in the "Barra" of the Ria de Aveiro (the link between the lagoon and the ocean) progressively led to a period of crisis that struck Aveiro until the 18th century, when the closure of the Barra became permanent. The construction of Barra Nova in 1808, along with the development of transport, especially the passage of the railway line Lisbon-Oporto, marked the beginning of a new era for the city [16].

This revival also coincided with the beginning of the industrialization process. During this phase, the city's expansion took place mainly in the northern part of the canal, with the formation of the Beira-mar district. From the last half of the 20th century onward, the population of Aveiro continued to grow steadily, with the creation of the university being a contributing factor.

#### **3.2 Building typologies and materials**

The predominant building typology in Aveiro is the so-called gothic-mercantile that, commonly, features living and dining rooms facing the street and kitchens placed at the rear of the house. All the rooms are connected by a long corridor perpendicular to the street. The buildings tend to have a single structural span, and they are inserted in narrow and deep lots attached to one another [17]. The height can vary from one story to a maximum of four, but the majority possesses two or three stories.

The influence of Art Nouveau is evident in the decoration of a significant number of constructions since the beginning of the 20th century. In the city of Aveiro, Art Nouveau was partially adapted to local traditions, creating a peculiar combination characterized by outstanding decorated façades and conservative interiors often built with poor local materials.

Indeed, the dominant construction technique relies on natural materials. Masonry with lime mortar was used for various buildings. Until the early 20th century, the Eirol stone was largely used for towers and aqueducts, whereas the Ança stone was commonly used for foundations, basements, and decorative elements [18].

Nevertheless, most of the buildings observed are characterized by the use of adobe blocks in the construction of the external walls. It has been estimated that around 25% of the existing buildings of Aveiro are made of earthen blocks, of which 40% are located in the city center, including most of the Art-Nouveau-style buildings. This is an extraordinary and distinctive feature of the city but also one of its main problems when it comes to conservation, with adobe being very vulnerable to water and considerably less resistant than stone. Only around the 1950s was adobe progressively replaced by reinforced concrete [19].

Along with adobe, the presence of pinewood can be observed in abundance, mainly for roofs, floors, and window frames of the buildings. It was implemented mainly with the tabique technique, one of the most traditional building techniques in Portugal. Less frequent but still present is the usage of brick, especially for public buildings [19].

#### **3.3 Flooding history**

The estuary area of the Ria de Aveiro is spread over about 11,000 hectares, more than 6000 of which is permanently covered with water. The surrounding area has low altitude and orographic relief, lacking natural protections against flooding. **Figure 3** shows the chronological distribution of the main urban-flood events occurred in the city of Aveiro.

Concerning the events before the 20th century, the documentation is scarce; therefore, fewer urban floods are recorded. However, it is known that a particularly great event occurred in 1739. Another one, in 1774, had terrible consequences as the Barra gave no outlet to the dammed waters and caused an epidemic that decimated the population.

In the 20th century, several flood episodes occurred. The most notable in terms of losses affected mainly the lower part of the city, with the historical city center being completely covered by water in 1937. Finally, severe floods struck Aveiro in 1955, 1957, 1964, and 1966, following strong storms and rise of water levels, and, more recently, in 1993, when the entire lower part of the city was inundated [20].

**Figure 3.** *Timeline of the major floods in Aveiro during the 20th century [20].*

*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*
