Flood hazard mapping of Vingunguti area in Dar es Salaam Tanzania

During heavy continuous rainfall natural watercourses like rivers and streams fails to contain all water hence excess water spill out and this leads to flooding. The study area was Vingunguti, found at Msimbazi valley in Dar es Salaam, which experiences flash floods occasionally. This leads to loss life, increased eruptional diseases, destruction of peoples’ properties, and interference of social and economic activities. In order to deal with the problem of flooding, this research aimed at producing flood hazard map which showed the extent and depth of flooding. To achieve this goal of flood hazard mapping, integration of GIS, ArcGIS extensions (HEC-GeoRAS), HEC-GeoHMS and Arc Hydro Tools), HEC-RAS hydraulic and HBV hydrological model were employed. Due to scarcity/absence of consistency discharge data at Msimbazi River, runoff was generated by using HBV rainfall runoff model from 44 years record length rainfall data. Flood frequency analysis was done in EasyFit Software, and 362.64m3/s flood peak was obtained for 100 years return period. In flood map generation, cross sectional and discharge data were imported to HEC-RAS model. In HEC-RAS model water surface elevations were created for the selected peak flood quantiles for 2, 5, 10, 25, 50 and years return periods. HEC-RAS results are the main input into HEC-GeoRAS and ArcMap in order to produce a flood hazard map. The produced flood hazard map showed inundation depth from 0.01m to 2.87m. This flood hazard map produced will save as a planning and decision tool for more effective flood management in Vingunguti area.