This paper presents a novel study of the Nature-based Solutions (NbSs) approach to analyze and propose mitigation measures for extreme floods. The study area is the Llobregat River in Catalonia, which crosses urban areas. We have selected one section in the final stretch of 4.5 km in the Barcelona Metropolitan Area. The section has suffered several damages in the last floods (e.g., 2016, 2018 and 2019), and we propose measures to reduce flood risk. Therefore, we proposed the following three specific objectives: (a) the identification of critical areas in the river stretches; (b) the identification of NbS opportunities and utilities; and (c) the mitigation measures in concrete areas from NbSs. The effectiveness of a NbS is based on the 2D simulation of the Gloria flood event (20–21 January 2020) with HEC-RAS software (version 6.0) for the better management of stormwater, and it is influenced by design and placement aspects; however, the better use of NbSs can improve flood mitigation and enhance urban resilience.

Urban complexity can be measured by the numerical and spatial diversity of activities in a territory. Just as biodiversity can be measured in a natural ecosystem, diversity indices can be applied to urban settings. Urban diversity presents higher values in areas where there is a greater number of (economic, institutional, and social) activities with a high degree of differentiation between them. This study seeks to investigate the potential of applying an urban diversity index in a specific case study: namely, the city of Barcelona (Spain), known for the orthogonal grid plan of its Eixample district. Results show that the municipal territory of Barcelona as a whole is characterized by highly differentiated spaces according to their urban diversity values. Specifically, it is the Eixample district that presents the highest values of urban diversity, reflecting the densification of its morphology and its urban commercial policies.

Cet article se concentre sur le cas de la zone métropolitaine de Barcelone, un exemple de régénération urbaine des cours d’eau (Llobregat et Besòs) dans le sud-ouest européen. Depuis l’approbation du premier plan d’expansion de Barcelone (Plan Cerdà, 1859) jusqu’à aujourd’hui, l’administration métropolitaine a essayé de gérer les zones fluviales en leur fournissant différents rôles (agricoles, industriels et récréatifs). Dans tous les cas, les deux cours d’eau partagent des interventions visant leur valorisation. Cet article vise à offrir une analyse historique de cette évolution de la place des cours d’eau dans la planification métropolitaine ainsi qu’à présenter les défis actuels et futurs du système fluvial de Barcelone.

The proper management of urban public services (UPS) ensures that a territory functions efficiently, since it guarantees optimal waste disposal, water supply, and the maintenance of communication infrastructure, among other things. In areas of high urban density located close to metropolitan cities, UPS are usually provided properly and efficiently. However, in less populated territories, lying in the periphery, significant problems and deficiencies are often encountered, being most evident in rural areas located on the administrative limits of a state or region. This paper seeks to analyze the management of UPS in the internal border area between two Spanish regions, Aragon and Catalonia. A total of 72 stakeholders (mayors and town clerks) from 49 river municipalities were involved in this study that employs a quantitative methodology (questionnaire). The perception that there are deficiencies to correct and a clear will to reach agreements and establish cooperation mechanisms is detected in many of the municipalities in the border area. A clear need to cooperate is also apparent in a series of priority UPS, including the promotion of river tourism, town access roads, urban collective passenger transport, and environmental protection.