Hydrological and hydraulic model for flood forecasting in Rwanda

This paper aims to forecast the Nyabugogo River flood risk and to propose mitigation measures that can reduce flood impacts using hydrological and hydraulic models. The annual Nyabugogo River floods that have led to human and economic losses are mainly due to the high topography, rainfall, soil texture and urbanization. It was found that the medium to high flood vulnerability is located in cropland, open grassland, open shrubland, settlement, sparse forest and wetlands. The results for 10-, 30- 50- and 100-year return periods show a slight increase in the flood inundation area and in water depth. The simulation shows that the 100-year return period gives a water depth of 3.24 m. Therefore, flood mitigation measures are needed, which can include the construction reservoirs upstream, relocation of infrastructures within the flood plain area, buffer zoning around the river, rainwater harvesting and raising public awareness. This paper provides basic support for decision-makers and can help in land use planning and flood management within the basin.