Implications of Combined Infrastructure Concentration and Interdependency for Extreme Event Recovery

Abstract

Infrastructure resilience in the context of extreme events is potentially affected positively or negatively by the combined effects of infrastructure concentrations and interdependence, occurring together. Concentration and interdependence are usually analyzed separately, and additionally, without reference to infrastructure resilience, an important need given the centrality of infrastructure to society. Concentration refers to density of facilities and/or operational controls and users at single points, extending the author’s previous research using broader geographic areas. Concentrations of economic activities, social settlements, and supporting infrastructures reflect traditional economies of scale. Alternatively, literature defines infrastructure interdependence as spatial, functional, or control connectivity. Resilience used here is recovery after destructive events, though the concept is broader. The methodology involves first, defining concepts and identifying actual, representative joint infrastructure concentration/interdependence combinations from cases. Second, key prototypes and typologies for concentrated, interdependent infrastructure combinations are developed and related to resilience (duration of postevent restoration and pre-event recovery), extending research considering them separately. Third, for quantitative analysis, databases are used to define and evaluate characteristics of different concentration/interdependence combinations e.g., recovery role (positive/negative), vulnerability to threats, tightness of combinations, and flexibility. Fourth, the role of adaptations, e.g., renewable resources and green infrastructure, in reducing or redirecting concentration/interdependence to promote positive impacts are discussed in terms of effectiveness at socioeconomic and technological interfaces. Finally, implications of concentration and interdependence combinations for infrastructure management and policy are presented. The methodology is applied and evaluated for transit ridership at NYC subway stations under normal conditions and disruptions such as an electric power outage. Results indicate that concentration and its effect on interdependence varies depending on assumptions about ridership redistribution during or following an outage.

Keywords: Urban infrastructure, infrastructure interdependencies, concentration ratios, electric power, transit