Risco hidrológico associado às incertezas na determinação do tempo de concentração: caso de estudo barragens na ilha de Santiago – Cabo Verde

Abstract

On the design of Saquinho Dam and Figueira Gorda Dam, located in Santiago Island in Cape Verde, the adopted times of concentration were calculated through the average of values done between each method adopted and the characteristics of the watersheds in which they wer e applied at, aiming to check if they were, indeed, suitables. Adopt the average between methods as the time of concentration is not a standard procedure and the dams already present signs of wear, then, it was decided to remake the design calculations usi ng the time of ter was kept as in the design for comparision purposes. The flood hydrographs were generated through HEC - HMS software, from the hyetographs generated by the designers, the same way as the design calculations. Results showed that most of methods do not have enough applicability information or are not appropriate for the watersheds concerned. The overestimaded value of time of concentration lead to smaller peak flows and smaller fl ood water levels. Consequently, the free board value was not respected, the dams are subjetc to overtopping, not presenting safety for a millennial flood, to which they were, initially, designed.