Risk-Based Decision Making Model for the Selection of Flood Mitigation Alternatives
In recent years, there has been a noticeable increase in the frequency of natural disasters such as wildfires, hurricanes and flooding, resulting in big economic, environmental, and social impacts. In the case of flood events, impacts such as community anxiety, loss of life, water pollution, and contamination of agricultural land have been found to be equally, if not more important, than the economic impacts of such events. Nevertheless, the literature shows that flood risk assessment studies incorporating economic, environmental, and societal impacts are limited. In addition, flood mitigation measures are typically compared focusing on economic criteria and not considering stakeholders or the implementation characteristics of the flood mitigation alternatives. This study proposes a holistic framework for watershed flood management that considers economic, social, environmental, and implementation criteria for selecting among flood mitigation alternatives. First, a spatial flood risk assessment framework capable of integrating economic, social, and environmental impacts is introduced in order to assess the possible losses and risks within the communities of a watershed. The risk assessment uses HAZUS software from the Federal Emergency Management Agency (FEMA) and is executed for five different return periods. Second, in order to select from multiple mitigation alternatives, a Decision-Making Models (DMM) is proposed. The first model uses the results from the risk assessment and the mitigation alternatives are evaluated using a Monte Carlo Simulation and probabilistic optimization. The second DMM model incorporates stakeholders characteristics and opinions using stakeholder theory, network analysis, and the Analytical Hierarchical Process (AHP). Two surveys were developed and deployed to public officials of agencies involved in the planning and implementation of flood mitigation alternatives and to the community, respectively. Along with this information, technical aspects of the flood mitigations alternatives are used as implementation criteria. Three alternatives were evaluated in the decision analysis: (1) no action, (2) flood warning system, and (3) levee. The framework is demonstrated with the case study of the Upper Río Grande of Loíza Watershed in the Commonwealth of Puerto Rico. The results showed that both stakeholder's input and implementation criteria can have a significant impact when selecting among flood mitigation strategies. For the case study, when considering economic, social, and environmental criteria, the 'Levee' was the alternative that minimized the flood risks. The developed framework was shown to be easily implementable and adaptable to Decision-Maker (DM) requirements. In summary, the model can provide DMs with the information they need in order to forecast the flood risks of a community and study the effects of the mitigation alternatives to be implemented. These results could be used for budget forecast, resource allocation and for establishing flood management priorities for a watershed.'
flood mitigation, decision making, risk assessment, flood impacts
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