ABSTRACT: Flood is one of the serious, common, and costly natural disasters. To provide effective risk assessment, it is necessary to be able to predict impact of flood events in the riverside areas. An important analyse tool is a geographical information system mainly with connection to numerical modeliing, where a results of an analysis is a flooding extent, water depth, velocity and possibility to model and predict impact to the environment. An example of mentioned tool is the ArcView 3.2 software with extensions HEC-GeoRAS and HEC-RAS 3.1 software for the flood simulation. HEC-GeoRAS is a suite of GIS pre- and post-processing tools for HEC-RAS, a one-dimensional river hydraulics model developed by the Hydrologic Engineering Center (US Army Corps of Engineers) and widely used in Civil Engineering practice. GeoRAS allows hydraulic engineers to use ArcView to develop HEC-RAS models integrated with digital terrain models and other GIS data sets. Automated GIS processing procedures in HEC-GeoRAS provides a valuable and instant method for repetitive hydraulic model development during floodplain analysis. Further, the GIS is ideally suited for visualizing of proposed alternatives and the associated flood impacts. HEC-GeoRAS Version 3.2 could be used to extract crosssectional station-elevation data from a digital elevation model (DTM) represented by a triangulated irregular network (TIN). Downstream reach lengths and bank station locations could be determined for each cross section using HEC-GeoRAS and Manning's "n" values could be extracted from land use data. The automated procedures for extracting geometric data proved consistent and efficient for the development of floodplain models to evaluate wetland scenarios.