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Methodology for evaluating flood damage reduction alternatives using a GIS-based MCDA interactive model

Abstract

Floodplain management involves the use of spatial physical information and information on decision makers' preferences. Both of these sources of information can have various degrees of imprecision. This research proposed a combined geographic information system (GIS) with Multi-Criteria Decision Analysis (MCDA). The use of GIS can give technical specialists and ultimately decision makers the possibility to find more spatially distributed information. These can be used to augment, an MCDA approach, which is an efficient tool for considering multiple-criteria in deciding on the best alternatives in a synthesized and integrated manner. The outcome of a floodplain management study is typically a recommendation for a single alternative flood management strategy. If this is developed by simply averaging over the entire floodplain, information is lost about the impact of the various alternatives on specific points in the floodplain. The ability to view this spatially distributed information could provide decision makers with a better understanding of the impacts of selected a specific alternative. Finally, a "cost of uniformity" metric is proposed that allows the decision makers to better determine the impact of selecting a single alternative for the floodplain by considering the spatially diverse information developed in the MCDA. The target region for a demonstration application of the methodology was the Suyoung River Basin in Korea. The 1991 Gladys flood event and five different return periods were used as a case study to demonstrate the proposed methodology of evaluation of various flood damage reduction alternatives. Through a case study, the characteristics of four different MCDA methods and the impact of inserting additional criteria into the MCDA are examined and compared. Based upon the comparison between the methods, it has been illustrated that the Improved Spatial Fuzzy Weighted Average Method using an S-shaped Membership Function applied to adjusted digital elevation maps provides enhanced information for evaluating flood damage reduction alternatives.

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Subject

decision support
flood damage
flood inundation
fuzzy
GIS
MCDA
MATLAB
civil engineering

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