A common difficulty in modeling hydrological systems is the lack of available field data to assess the model parameters. In some cases, it is physically very difficult and expensive to obtain sufficient and accurate field data. In the absence of field data, the model parameters can be obtained either using topographic maps from aerial photography or satellite imagery such as digital terrain models. An alternative approach to assessing model parameters is the use of optimization techniques. In this study, optimization methods have been employed to estimate the model parameters used in a flood routing equation for the Blue Nile river system in Ethiophia.