Earthen vernacular architecture in flood-prone areas: characteristics and typologies in the Ebro basin

Earthen architecture is one of Spain's longest-standing construction traditions, used from antiquity to the mid-twentieth century. Given its hygroscopic nature, earthen architecture is generally seen as barely resistant to water and as more associated with geographical areas with hot and dry climates. However, it is found in different places with different climate and geographical characteristics. In these surroundings, its survival over time has been ensured by a process of adaptation and modification producing architectural and constructive forms which reflect the identity of the geographical areas in question. One of the main risks to earthen architecture are floods, which have always represented a threat to this architectural heritage. The increased frequency and intensity of floods due to climate change have in turn gradually given rise to an increasing risk of disappearance for this architectural heritage. This paper aims to study the typologies and features of earthen vernacular architecture in flood-prone areas through the analysis of case studies in the Ebro basin. The study of earthen buildings in the area under study provides information on the most recurrent architectural features and vulnerabilities, as well as the inherent resistance which has enabled this earthen architectural heritage to survive. Moreover, a study of the pathologies and structural damage visible on buildings highlights those which are a direct consequence of the action of water and can potentially affect structural behaviour during a flood. Aiming to establish conservation strategies for earthen architectural heritage the data collected are analysed using a qualitative vulnerability assessment methodology, establishing the degree of influence of individual characteristics on the response of earthen structures to floods.