To study the utilisation of GIS technology for flood modelling and the floodplain mapping process, a tool based on the loose coupling of a river model (NOAH 1D) and GIS (ArcView GIS), NOAH-GIS, has been developed. NOAH-GIS can be used to prepare hydraulic model requirements (i.e. geometric data) and to generate floodplain inundation maps from the river model results within ArcView GIS. A framework, linking NOAH 1D to a brand new GIS software, ArcGIS, has also been developed to perform the same tasks (NOAH-ArcGIS map template). These tools have been used to demonstrate the floodplain mapping process for a test catchment, the Ouseburn catchment, Newcastle, UK for a design flood (the 1 in 100-year event). Date requirements (i.e. topographic and hydrologic data) have been developed for the hydraulic modelling in NOAH 1D. The development of the floodplain mapping tools, the data preparation and the application allowed the investigation of (1) pitfalls involved in the floodplain mapping technique, (2) limitations of modelling methods and (3) errors that may occur during the modelling and mapping process. This also provided an increased understanding of the data requirements and the floodplain mapping technique. It is clear from the study that topographic and hydrologic data and hydraulic model are essential issues and play a vital role in the floodplain mapping process. A correct interpretation of the floodplain inundation map and the elimination of error due to modelling are crucial in order to provide the most accurate information. Observation data are shown to be valuable for a more realistic estimation. Finally, several presentation techniques for the display and visualisation of the results were developed, which are of value for observing the areas of interest from different perspectives.