GRIN Verlag Flood Forecasting, Conterol and Modeling for Flood Risk Management Systems: Flood Control in Fogera Area under Regulatory Operations of Planned Gumara and Ribb Reservoirs, Upper Blue Nile, Ethiopia

Scientific Study from the year 2011 in the subject Geography / Earth Science - Regional Geography, grade: 7.70, , course: Water Science and Engineering-Hydroinformatics, language: English, abstract: A brief overview of flood control in Fogera plain, upper Blue Nile, Ethiopia is presented as the context of understanding the causes of flood problems and their solutions. The runoff from upstream Gumara and Ribb watersheds, runoff from direct rainfall, and overflows from Lake Tana along the shoreline are the main causes of flooding in the area. The most likely reasons are related to the frequent changes of catchment characteristics, agricultural development of the area, population growth and other interrelated factors. Owing to the adverse nature of flooding events, this study was focused on developing a flood control strategy under regulatory operations of the proposed reservoirs, Gumara and Ribb reservoirs, and understanding the flood behavior to reduce flood risks. The methodologies adopted were a hydrological model in HEC-HMS to generate runoff in the watersheds, simulations of the proposed reservoirs by imposing a separately developed reservoir operation rule curves. Reservoir operating rule curves were developed using Discrete Dynamic Programing (DDP). Reservoir operating rule curves play a significant role to control floods downstream. Lastly, hydrodynamic flood modeling with SOBEK 1D/2D was used in order to understand the flow dynamics and flood characteristics (such as flood extent, inundation depth and flow velocity) that enables to implement possible flood protection measures. According to this study, the combined model results were shown that the flood extent is reduced by approximately 26% due to the presence of the planned dams compared to the results without these proposed dams or the existing condition. If economically and technically feasible, some relevant mitigation measures, engineering and non-engineering measures, were proposed to reduce the