Overview. Introduction to floodplain mappingWhy use GIS?ProblemsTools and DataProcessResultsFutureQuestions. Floodplain Mapping Process. Gather DataHydrologic AnalysisHydraulic AnalysisMap Floodplain Using Outputs and Base Maps. Why Use GIS?. Delineation of watershed boundaries and parameter estimation is simplifiedInput of topographic data far less labor intensiveImport and Export of data between ArcView and HEC-HMS and HEC-RAS is convenientAmount of labor associated with hand delineation makes adjustments cost-prohibitive .