Modeling Flood Hazard Zones at the Sub-District Level with the Rational Model Integrated with GIS and Remote Sensing Approaches

Daniel Asare-Kyei,Gerald Forkuor,Valentijn Venus

doi:10.3390/w7073531

Abstract

Robust risk assessment requires accurate flood intensity area mapping to allow for the identification of populations and elements at risk. However, available flood maps in West Africa lack spatial variability while global datasets have resolutions too coarse to be relevant for local scale risk assessment. Consequently, local disaster managers are forced to use traditional methods such as watermarks on buildings and media reports to identify flood hazard areas. In this study, remote sensing and Geographic Information System (GIS) techniques were combined with hydrological and statistical models to delineate the spatial limits of flood hazard zones in selected communities in Ghana, Burkina Faso and Benin. The approach involves estimating peak runoff concentrations at different elevations and then applying statistical methods to develop a Flood Hazard Index (FHI). Results show that about half of the study areas fall into high intensity flood zones. Empirical validation using statistical confusion matrix and the principles of Participatory GIS show that flood hazard areas could be mapped at an accuracy ranging from 77% to 81%. This was supported with local expert knowledge which accurately classified 79% of communities deemed to be highly susceptible to flood hazard. The results will assist disaster managers to reduce the risk to flood disasters at the community level where risk outcomes are first materialized.

Highlights

IntroductionIn the last three decades, the sub-region has witnessed a dramatic increase in flood events, with severe impacts on livelihoods, food security and ecological systems [2,3,4]
West Africa is prone to frequent floods and droughts due to high variability in rainfall patterns [1].In the last three decades, the sub-region has witnessed a dramatic increase in flood events, with severe impacts on livelihoods, food security and ecological systems [2,3,4]
This study has drawn on the strengths of a simple hydrological model and statistical methods integrated in Geographic Information System (GIS) to develop a Flood Hazard Index to an acceptable accuracy level

Summary

Introduction

In the last three decades, the sub-region has witnessed a dramatic increase in flood events, with severe impacts on livelihoods, food security and ecological systems [2,3,4]. Normal rainfall amounts at the peak of the rainy season in the Sudanian and Sahelian regions (i.e., July to September) frequently lead to severe floods, and cause many of the major rivers (e.g., Niger, Volta river systems, Senegal) to overflow their banks. In 2007, for example, a series of anomalous abundant rainfall events caused severe floods in West Africa (WA) and other parts of Sub-Saharan Africa (SSA) which affected more than. In 2012, flooding along the river Niger, which is the principal river in West Africa, resulted in the death of 81 and 137 people in

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Results

Conclusion