Flooding is one of the serious, common, and costly natural disasters that many countries are facing. One of the non-structural measures for risk reduction is the delineation of flood-prone areas. Flood risk mapping involves modeling the complex interaction of river flow hydraulics with topographical and land use features of the floodplains. From conventional flood hazard mapping technique based on field investigation to a knowledge-based system, the study integrated the hydraulic model with the Geographic Information System (GIS) and presented a systematic approach of this application with a case study of Lakhandei River in Nepal. The study focused on the preparation of Triangulated Irregular Network (TIN) from available cross section data, contours and spot elevations, calculation of water surface profiles by steady and unsteady flow analysis, delineation of the flood areas, risk mapping, and creation of flood animation. The approach adopted for the study consisted of dividing the risk into vulnerability associated with land use pattern and hazard associated with hydrological and hydraulic parameters. The results of these analyses were combined to see relationships such as discharge-flood area and flood depth-land use. A series of maps were prepared depicting different relationships, such as discharge-flood area and flood depth-land use. This provided a framework that would help administrators and planners to identify areas of risk and prioritize their mitigation and response efforts. This would also raise the public?s awareness of flood risks and enable them to prepare mitigation activities. The research also prepared a general flood action plan. Using satellite images, the study further assessed changes in river course.