Abstract:
The hydrologic behavior of the Addis Ababa urban watershed was characterized as
subtle charter, with the objective of evaluating the hydrologic impacts of the
increasing of the impervious area within its watershed and other factors. In order to
decide on minimizing the impact of floods and to know the impact of urbanization on
flood volumes and peak discharges, an effective flood volume estimation model is
required. Towards this end, HEC HMS rainfall run off model has a great potential to
quantify the actual increase river flow in urban development over the past 4 decades
and including the future land use impact. This study of Addis Ababa will; gather IDF
curve precipitation data for the watershed, generate a database using appropriate
software, estimate flood volume, show urbanization effect on flood and use the
model to simulate potential future effects on the Addis Ababa watershed using HEC
HMS. Arc GIS, a software mapping tool using land use, soils, and property
boundaries, facilitates definition of watershed hydrologic parameters and allows
these parameters to be incorporated into HEC-HMS. Finally all the existing information related to the historical floods that have happened in the city during the
studied period, as well as the historical evolution of land uses, was compiled and by
running the model the result was compared at each junctions of the Addis Ababa city
for each land use period. Therefore comparing the results of the model, the author is
able to successfully establish the concern for increasing river flows due to
urbanization. The results of this study will encourage emergency managers and local planning
authorities to consider land use planning as an effective measure for flood risk
