Spatial floodplain modeling using GIS technique: a case study of the lower Rufiji floodplain Tanzania

The Lower Rufiji Floodplain is normally flooded during the two rainy seasons experienced in Tanzania. The work described in this dissertation is concerned with the spatial modeling of floods in the Lower Rufiji Floodplain using Geographical Information Systems (GIS)-based tools. Using the ArcView GIS software and the HEC-GeoRAS extension support, river and floodplain geometric data were extracted from the Triangular Irregular Network (TIN) model of the river and the floodplain. The geometric data was imported to HEC-RAS as a GIS import file. The hydraulic data, boundary conditions and flow data were completed in HEC-RAS and water surface profiles were simulated for various flow scenarios. Computed water surface profiles were exported to ArcView GIS and using the HEC­ GeoRAS extension, two-dimensional flood extent maps and three-dimensional flood depth maps were produced for the entire floodplain stretching from Stiegler's Gorge to the delta area. The maps were generated for thirteen flow values ranging from I 000 Cumecs to 7000 Cumecs at intervals of 500 Cumecs.