Assessment of Anticipatory Approach Using the Integration of GIS, and Remote Sensing Techniques for Flood Management in Alexandria City, Egypt

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Alexandria city is the second largest city in Egypt; located on Mediterranean Sea. It experienced yearly extreme rainfall events. In 2015, it was hit by an extreme rainfall, causing a heavy impact flooding on the most urban areas of the city. This causes a huge negative impact on the social and economic activities. The responsible authorities did not prepare enough for this extreme event. This study aims to assist decision makers to prepare priority plans by developing flood susceptibility mapping for Alexandria city, using Geographic information system (GIS), remote sensing applications (RS), and integration with multi-criteria decision-making method. The analytic hierarchy process (AHP) techniques, and the list of significant urban flood factors are developed following a review of the related literature and a technical discussion with experts from the water sector. The required data for each factor were derived by remote sensing techniques. A quantitative analysis using the analytical hierarchy process (AHP) method was used to derive the final weights for each factor. A spatial data analysis was performed to identify different factors of the susceptibility map using the GIS system. Finally, the study has shown that the rainfall amount factor has the highest probability of flooding with a priority weight of 38%; this is because of its importance in the flood trigging, trailed by distance to stream with weight 26.3%, and the slope with weight 13.4%. Land cover-land use and elevation were the least important factors with priority weightings of 11.5%, 10.8% respectively. The developed susceptibility map classified the Alexandria city into zones regarding its likelihood risk of urban flooding to three grades, as high, moderate, and low. The purpose of this classification is to help decision-makers in preparedness for flood mitigation.