Floodplain Analysis Using Computational Tools

When conducting hydraulic studies or floodplain analysis or when producing DFIRMs for the FEMA map modernization program, two of the more time-consuming processes are setting up the hydraulic model and delineating the floodplain zones. The integration of widely available computational tools with hydrologic and hydraulic modeling and floodplain mapping improves accuracy, effectiveness, and quality. The various tools discussed in this paper include HEC-GeoHMS, HEC-GeoRAS, WISE, CHECK-RAS and RASPLOT. In this paper, the county-wide draft DFIRM of Scott County, Minnesota, is used to demonstrate the applications, capabilities, and challenges faced when using these tools. By using Geographic Information Systems (GIS) raster and feature data sets, HEC-GeoHMS and HEC-GeoRAS automate the pre-processing of input data and post-processing of HEC-RAS results. CHECK-RAS is used to verify the validity of hydraulic parameters, structure and cross section data, as well as floodway and flood profile results. RASPLOT facilitates the creation of flood profiles. These tools are successfully linked with HEC-RAS to expedite the production of floodplain mapping and obtain accurate hydraulic results.