Comparative Evaluation of Global Flood Hazard Maps and Recommendations for Corporate Practice

Abstract

　In developing countries in Asia and Africa, where flood risk information is insufficiently obtainable, companies often use available flood hazard maps developed from the Global Flood Model (GFM). As described, this study compares existing flood hazard maps based on GFM used in business practice. Then the factors causeing differences in inundation areas and depths are analyzed, particularly addressing the model structure and input data. Results indicate that inundation patterns in low-lying areas are affected by the accuracy of elevation data and that the methods of reflecting flood protection information differs greatly among GFMs. The results also suggest that the consideration of backwater effects in river sections near large lakes and the consideration of channel bifurcation in delta areas are necessary to obtain realistic inundation distributions. Based on these findings, we propose a flow of selecting a flood hazard map to be used in corporate practice. Although no single map can be recommended for all purposes, the benefits and shortcomings of each map can be listed for objective prioritizeation of maps that should be used. The outcome of this study can be extended to the use of other risk maps including paid products, and might provide fundamental scientific information for use in the implementation of appropriate and accountable flood risk assessments.