River Inundation and Hazard Mapping – a Case Study of Susan River – Kumasi CollinsFosu 1 , Eric K. Forkuo 2 and Mensa Y. Asare 3 Department of Geomatic Engineering, Kwame Nkrumah University of Science & Technology, Private Mail Bag, Kumasi, Ghana Email: 1 fosucoll@hotmail.co, 2 eforkuo.soe@knust.edu.gh.com, 3 asare.mensah@csrdevelopments.com Abstract In recent times there have been extreme climatic conditions due to climate change. As a result of this, the intensity of rainfall has increased tremendously causing floods in many areas and countries worldwide. It is therefore prudent that such a natural hazard is addressed in a way to reduce the impact it causes on people and the environment. To achieve the aim of river modelling and hazard mapping using a Geographic Information System, spatial technology and the HEC-RAS hydraulic model were used as tools. In this research, a DEM which is basic input for any effective flood modelling was created from contour data. The geometric data needed for the modelling process were extracted from the DEM, topographic map and field measurements. A remotely sensed image was classified into various land cover types which was used for estimating the roughness coefficient of the various cover types during the modelling process. The model results were displayed and analysed in ESRI ArcGIS environment. The flooded area was geometrically overlaid on the topographic map to delineate the affected buildings. The hazard map produced clearly shows the spatial distribution of the flooded area which is located at areas with relatively low relief. The total flooded area covers an approximately 2.93km2. Also a flood depth of 4.01637 was obtained as the maximum water level. Generally, high water depth occurred along the main channel and spreads gradually to the floodplains. Keywords: Flood Modelling, DEM, Hydraulic Model, GIS, Hazard Mapping, River Inundation 1.0 INTRODUCTION Flooding is one of the serious natural hazards in the world (Seyedeh et al, 2008), and it accounts for 40% of all deaths caused by natural disasters, with most flood events occurring in developing, tropical regions (OhlandTapsell, 2000). Floods are of many types including flash flooding (Gruntfest and Handmer, 2001), flood- ing due to rising ground water (Burt et al., 2002), coastal flooding (Nicholls, 2002)