Accra Flood Modelling through Application of Geographic Information Systems (GIS), Remote Sensing Techniques and Analytical Hierarchy Process

Abstract

Urban Flooding is one of world’s problems in recent times because of its frequent occurrence which results in loss of lives and properties. The first step in flood management is the development of hazard maps. Flood hazard mapping forms the foundation of the decision-making process by providing information which is essential to the understanding of nature and characteristics of flooding to risk community or city. Flood modelling is a complex problem and therefore a lot of factors should be considered before the final map showing flood prone areas are produced. The degree at which each of these factors contributes to flooding must be weighted by using multi decision process before incorporating them in an integrating environment such as GIS to produce the final prediction map. In this study, this approach was employed by using GIS and Analytical Hierarchy Process (AHP). The layers that were used in the flooding included; Slope, Drainage basin, Rainfall, Soil, Land Use and Digital Terrain Model (DEM). The result obtained was more accurate as compared to the previous works done on Accra flooding. This is because more than one contributing factors were considered and at the same time, weights were assigned to these contributing factors before overlaying them to produce the final map. The previously occurred flood places were all found in the high possibilities flooding zones. The flood prone map indicates that almost the whole area of Accra and Greater Accra Region has a possibility of flooding. However, the riskiest areas are Accra Metropolitan, Ledzokuku Krowor, Ga West and Ga South.