Embankment Dam Spillway Adequacy Evaluation under Probable Maximum Flood the Case of Tendaho Dam, Ethiopia

Abstract

Embankment dams constructed in flood prone areas have high probability of overtopping if their spillway is not designed to pass the maximum flood. Checking adequacy of spillway helps to pre plan mitigation measures if there would be failure. This study evaluates adequacy of embankment dam spillway to pass PMF using HEC-HMS model taking Tendaho embankment dam constructed on lower Awash River in Ethiopia as case study. The spillway of the dam was constructed in flood susceptible area to pass 10,000 years' flood. The model was calibrated and validated using twenty-four rainfall stations in the catchment and nine years observed flow data at tendaho station. The result of the study indicates that there would be overtopping of the dam under PMF with 20cm and hence inadequacy of Tendaho embankment dam spillway to pass PMF.