Determination of the flood volume by the aspects of peak flow and flood hydrograph at the level of the city of Biskra, Wadi Biskra watershed, Algeria.

Abstract The peak flow of a flood can be determined by several empirical methods. Among these methods, the Gradex method is used in this work to estimate the project flood and the volumes corresponding to the flows. This approach has made it possible to recognize the flow of different frequencies by aspects of the peak flow and the flood hydrograph. The study was based on the maximum annual daily rainfall for a long series of observations (47 years), and on the intensity-duration-frequency (IDF) curves of the four rainfall stations Biskra, T'kout, Djemoura, and El kantara; located in the watershed of Oued Biskra. The application of the Gradex method has allowed to approach the maximum flow of floods at the level of the outlet which is located at the entrance of the city of Biskra; for the rare frequency of occurrence (return periods ranging from 10 to 1000 years).