A new approach to assess cascading effects of urban floods

Abstract

The occurrence of floods has always represented a challenge to cities, with long-term impacts that are usually neglected, such as the degradation of the urban environment and the impoverishment of the population due to recurrent events. Besides the losses usually computed in flood damage assessment, there are also secondary effects, but not less important, resulting from failures of critical infrastructures, such as power supply, which generate diseconomies to the system. Thus, power outage can aggravate the effects of floods, reducing income generation, and consequently the population’s recovery capacity. Going beyond the “domino effect” metaphor, in which the disruption of a system can cause a chain of similar events disrupting other systems, this paper aims to expand the concept of cascading effects by considering not only the spatial approach that affects other urban services, but also incorporating temporal analysis. The main purpose, in this case, is to identify regions in which flooding is a catalyst for social impoverishment. Through hydrological and hydraulic modeling, the cascading effects can be interpreted as a series of interconnected events that are triggered by flood events and aggravated by their recurrence, what make it difficult or even impossible to recover from losses. The main innovation of the approach is the proposition of a global index to assess the watershed recovery deficit considering a sequence of flood events. Moreover, the results highlight that although the direct impacts of floods are more significant, the impact of power shortage worsens the societal situation.