Dam breach modeling and inundation mapping, a case study on Gidabo dam

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Preparing dam safety plans and hazard management strategies are unquestionably vital, since lots of human lives have been lost and tremendous amount of economic crisis have been recorded from dam failure events throughout the world in history. Setting out risk management, emergency action plans or evacuation planning system to protect both lives and materials during sudden dam failure phenomena and resulting flood waves is highly essential. This thesis addresses pre-event analysis of a dam breach scenario which is currently under construction in the Sidama zone of SNNPRS, the Gidabo dam. The paper focuses on overtopping and piping as the possible reasons of breach and identifies the inundation properties for a bunch of breach parameters suggested by five different scholars.This has resulted in ten computer runs where halves are for piping and the rest halves for overtopping. The objective is to arrive at possible dam breach parameters when calculated by different methods and to route the resulting flood through this calculated dam openings and to the downstream extents. This routed flow has resulted in almost same inundation extents by all of the methods. In addition the paper compares the breach results when analyzed by physical based model “breach model” and non-physical based models. HEC-RAS Ver 5.0 is used to model the dam failure. HEC-GEORAS Ver 10.0 is used with ARC-Map 10.0 to extract basic geometric data for use in HEC-RAS. A DEM is used as a terrain map to be used in ARC-Map. The process of gathering and preparing data, estimating breach parameters, creating an unsteady flow in HEC-RAS, dam breach parameters entry, performing a dam failure analysis for two scenarios and mapping of the flood inundation are discussed in this paper. The four non physically based empirical methods have resulted in peak flow values within a range of 24966.21 m3/s and 16039.97 m3/s during overtopping and 17348.94 m3/s and 9843.82 m3/s during piping. This results can be said more close when compared with the physically based model results. In conclusion, In any dam breach study, it would be good to check the breach by different scenarios, to see the range of hazardness when treated with different methods and to point out the optimal catastrophe so that emergency action planning preparation will be economical and safe. The area below the dam is relatively flat and people living on this area, specially near the river banks, shall be resettled at significantly far place. Key words: HEC-RAS, DEM, HEC-GeoRAS, Dam Failure, Breach, Dam Break Analysis, Scenario, GidaboDam.



HEC-RAS, DEM, HEC-GeoRAS, Dam Failure, Breach, Dam Break Analysis, Scenario, GidaboDam