Are we preventing flood damage eco-efficiently? An integrated method applied to post-disaster emergency actions
Graphical abstract
Introduction
Climate change and the increase in urban population pose a problem to flood risk management. By 2050 cities are expected to host 70% of the world's population (UN, 2012), resulting in more urban infrastructure and altering soil infiltration and natural watercourses. Floods are responsible for 34% of the global natural disasters (Guha-Sapir et al., 2009), and their management is especially complex in urban areas. The Spanish Mediterranean coast is an example. In this region, ephemeral streams are common hydrologic features that are typically dry except during torrential rainfall events that result in flooding. Some of the factors that increase the occurrence of these events are land use change, vegetation and soil removal and the construction of drainage networks. Therefore, prevention and mitigation strategies are essential for managing floods and reducing urban and natural damage (Barbosa et al., 2012). In the case of Spanish ephemeral streams, some engineering solutions include channeling or undergrounding the stream or regular maintenance activities. Still, flood damage amounts to 3E + 09 USD/year worldwide (around 2.6E + 09 euros - €) (Guha-Sapir et al., 2009). In Spain, the average insurance compensations for flood damage (e.g., lost properties, vehicles, etc.) reached 150 million euros/year from 1990 to 2014 (Insurance Compensation Consortium, 2015).
In the framework of sustainability, the consequences of flooding result in environmental and economic impacts at two different scales. On the one hand, damaged goods such as buildings or personal properties must be replaced or re-constructed, which requires materials, energy and money. On the other hand, prevention and mitigation strategies are often associated with investing physical and monetary resources for designing and constructing infrastructure. At this point, it is interesting to determine the environmental and economic balance of prevention and mitigation strategies with respect to the damage that they might prevent.
Existing articles proposed methods for integrating flood risk, prevention and damage. Most of the analyses simulated the hydrologic performance of different scenarios based on climate change predictions, control policies or alternative management systems and provided socio-economic results (Brouwer and van Ek, 2004, Haynes et al., 2008, Jonkman et al., 2008, Kubal et al., 2009, Zhou et al., 2012). These might include physical (e.g., building damage) and/or intangible costs (e.g., traffic delays or impacts on health). Cost-benefit analysis was usually the method applied to determine the economic feasibility of management alternatives (Jonkman et al., 2008, Zhou et al., 2012). The integration of environmental or ecological damage is more complex, but some studies attempted to include this dimension by estimating the potential damage to groundwater or biodiversity, for example (Brouwer and van Ek, 2004, Kubal et al., 2009). However, we still need to clearly define the environmental and economic impacts of flood prevention strategies in terms of investment and damage generation. In this context, post-disaster emergency actions are a field to explore, as the urgent need for urban restoration might lead to the application of economically and environmentally inefficient strategies.
To determine the environmental and economic investment in infrastructure, life cycle assessment (LCA) and life cycle costing (LCC) are commonly applied. Several studies on best management practices dealt with innovative systems, such as green roofs and retention systems (see for instance Flynn and Traver, 2013, Kosareo and Ries, 2007, Petit-Boix et al., 2015), but rehabilitation or post-disaster restoration strategies were not assessed, and neither were flood damage costs. However, this analysis is essential to provide an estimation of the eco-efficiency of the strategies, which is a measure of the environmental performance of a system in relation to its value (ISO 14045:2012) that helps to determine its feasibility through a bi-dimensional approach. When dealing with post-disaster emergency actions, this assessment should help reduce the economic investment while generating fewer environmental impacts. To our knowledge, the eco-efficiency approach was not applied to flood studies in the past.
This paper seeks to integrate post-disaster emergency actions and flood damage generation in hydrologic, environmental and economic terms with the aim of eco-efficiently planning prevention strategies in the future. We try to answer the following question: Are post-disaster emergency actions feasible when compared to the economic and environmental damage generated by floods? Our goal was to provide a method for estimating the environmental and economic balance and payback period of flood prevention from an eco-efficiency standpoint. This approach might facilitate and foster eco-innovation in the field of disaster management. We tested this method in the coast of Catalonia (Spain), where the combination of torrential rainfall and urbanized ephemeral streams poses a significant risk. This analysis was based on historical data and specific torrential events, as previous hydrologic analyses identified the need to focus on particular damaging events and their associated consequences instead of providing general inaccurate statistics (Olcina and Rico, 2000).
Section snippets
Methods
Fig. 1 illustrates the method applied for estimating the environmental and economic balance and payback period of implementing post-disaster emergency actions. The application of the method is detailed in the following sections.
Results and discussion
In this section we present the hydrologic evaluation of the watershed (Section 3.1), the impacts associated with the investment in infrastructure (Section 3.2) and damage compensation (Section 3.3) and the economic and environmental feasibility of the actions (Section 3.4).
Conclusions
The results obtained in this paper highlight the effects of integrating the consequences of decisions into the life cycle of urban interventions, such as flood prevention strategies. Accounting for costs and benefits is especially common in companies, where revenue can easily be calculated and balanced with the investment. However, it is also interesting to couple these parameters at an urban scale, as they might be responsible for a share of the total impacts of cities. Thus, this type of
Acknowledgment
We wish to thank the Catalan Water Agency and the Insurance Compensation Consortium for supporting and providing data, especially Alfonso Nájera. We thank Dr. Jorge Olcina and Dr. David Saurí for their valuable advice in the field of flood management. We would also like to thank the Spanish Ministry of Education for the grant awarded to A. Petit-Boix (FPU13/01273) to conduct this research, and the Catalan Government for the SGR funds (2014 SGR 1412), as well as the grant awarded to A. Arahuetes
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