Flood Risk Assessment in an Underground Railway System Under the Impact of Climate Change—A Case Study of the Barcelona Metro
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sustainability Article Flood Risk Assessment in an Underground Railway System under the Impact of Climate Change—A Case Study of the Barcelona Metro Edwar Forero-Ortiz 1,2,* , Eduardo Martínez-Gomariz 1,2 , Manuel Cañas Porcuna 3, Luca Locatelli 4 and Beniamino Russo 4,5 1 Cetaqua, Water Technology Centre, Carretera d’Esplugues, 75, 08940 Cornellà de Llobregat, Barcelona, Spain; [email protected] 2 Flumen Research Institute, Universitat Politècnica de Catalunya, Calle del Gran Capità, 6, 08034 Barcelona, Spain 3 TMB (Transports Metropolitans de Barcelona), Carrer 60, núm. 21-23, sector A, Pol. Ind. de la Zona Franca, 08040 Barcelona, Spain; [email protected] 4 AQUATEC (SUEZ Advanced Solutions), Paseo de la Zona Franca, 46-48, 08038 Barcelona, Spain; [email protected] (L.L.); [email protected] (B.R.) 5 Grupo de Ingeniería Hidráulica y Ambiental (GIHA), Escuela Politécnica de La Almunia (EUPLA), Universidad de Zaragoza, Calle Mayor, 5, 50100 La Almunia de Doña Godina, Zaragoza, Spain * Correspondence: [email protected] or [email protected]; Tel.: +33-783-53-72-22 Received: 19 May 2020; Accepted: 28 June 2020; Published: 30 June 2020 Abstract: Flooding events can produce significant disturbances in underground transport systems within urban areas and lead to economic and technical consequences, which can be worsened by variations in the occurrence of climate extremes. Within the framework of the European project RESCCUE (RESilience to cope with Climate Change in Urban arEas—a multi-sectorial approach focusing on water), climate projections for the city of Barcelona manifest meaningful increases in maximum rainfall intensities for the 2100 horizon. A better comprehension of these impacts and their conditions is consequently needed. A hydrodynamic modelling process was carried out on Barcelona Metro Line 3, as it was identified as vulnerable to pluvial flooding events. The Metro line and all its components are simulated in the urban drainage models as a system of computational link and nodes reproducing the main physical characteristics like slopes and cross-sections when embedded in the current 1D/2D hydrodynamic model of Barcelona used in the project RESCCUE. This study presents a risk analysis focused on ensuring transport service continuity in flood events. The results reveal that two of the 26 stations on Metro Line 3 are exposed to a high risk of flooding in current rainfall conditions, and 11 of the 26 stations on Metro Line 3 are exposed to a high risk of flooding in future rainfall conditions for a 20-year return period event, which affects Metro service in terms of increased risk. This research gives insights for stakeholders and policymakers to enhance urban flood risk management, as a reasonable approach to tackle this issue for Metro systems worldwide. This study provides a baseline for assessing potential flood outcomes in Metro systems and can be used to evaluate adaptation measures’ effectiveness. Keywords: flood risk assessment; climate change; 1D/2D hydrodynamic model; Metro system; subway; urban mobility 1. Introduction Current trends in the analysis of climate-driven events on urban societies, infrastructures, and services have guided study towards the direct and indirect impacts of these events, resulting in Sustainability 2020, 12, 5291; doi:10.3390/su12135291 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 5291 2 of 26 disruptionsSustainability 2019 within, 11, xthe FOR interdependent PEER REVIEW infrastructure systems. 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According to 2018 figuresMetro [6], 178 systems’ cities in importance 56 countries worldwide have a Metro for transportation cities’ operability system, is withevident. an average According ridership to 2018 of 168figures million [6], per178 day,cities and in 56 increasing countries annual have a useMetr ofo 19.5%.transportation Figure1 system,presents with the currentlyan average in-service ridership numberof 168 million of Metro per systems day, and in increasing Europe. Between annual China,use of India,19.5%. and Figure Iran, 1 Asiapresents is building the currently 16 new in-service systems, shapingnumber theof Metro decarbonizing systems in urban Europe. transport Between eff ortChina, as a India, response andto Iran, climate Asia changeis building [6]. 16 new systems, shaping the decarbonizing urban transport effort as a response to climate change [6]. Figure 1. Metro systems in operation in Europe by 2019 [6]. Figure 1. Metro systems in operation in Europe by 2019 [6]. Following the accelerated growth of cities and their Metro systems, and the increasing growth and complexityFollowing ofthe Metro accelerated networks, growth the abilityof cities to and study their and Metro improve systems, the vulnerability and the increasing of systems growth are moreand complexity complex, according of Metro networks, to the heterogeneity the ability to of study the di andfferent improve components the vulnerability of a large of scale systems system, are suchmore as complex, a transport according network to [the7]. heterogeneity The probability of ofthe disruptions different components should consider of a large many scale factors, system, not such as a transport network [7]. The probability of disruptions should consider many factors, not only the number of affected Metro stations, but also the distance between them [8], along with several other factors. Sustainability 2020, 12, 5291 3 of 26 only the number of affected Metro stations, but also the distance between them [8], along with several otherSustainability factors. 2019, 11, x FOR PEER REVIEW 3 of 26 Considering hazards that Metro systems face worldwide, there is a notable lack of research on water-relatedConsidering hazards hazards [5], including that Metro those systems related face to floodingworldwide, events there and is a their notable impact lack on of Metro research systems’ on resiliencewater-related [9]. Inhazards a context [5], including of climate those change, related flooding to flooding events events can produce and their increasing impact on significant Metro socioeconomicsystems’ resilience risks in[9]. urban In a areas. context Worse of climate still, urbanization change, flooding heightens events the likelihood can produce of water increasing disasters suchsignificant as floods socioeconomic because development risks in urban decreases areas. Worse the amounts still, urbanization of