SUMMARY
This paper presents a Flood Frequency Analysis (FFA), which takes into account the notion of characteristic duration. Instantaneous flood discharge data from Foum El Gherza station is used to develop flood-duration-frequency (QDF) curve, using the so-called converging model. Seven distributions widely used in FFA were considered in this study: The generalized extreme-value (GEV), Normal (NORM), Gumbel (Gumbel), two parameter log-normal (LN), Pearson type III (P3), Log Pearson type III (LP3) and Frechet (EV2). Different models selection criteria were applied, e.g. Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC) and Anderson-Darling Criterion (ADC). The results showed that the Pearson type III (P3) distribution is the more appropriate to fit the considered data. QdF curves were fitted. Synthetic Mono-Frequency Hydrograph (SMFH) was then derived after the estimation of the characteristic duration of the watershed using the mean of non-dimensional hydrographs and the socose method. The main advantage of these hydrographs is that all the characteristics of the SMFH are related to the same return period. These design flood hydrographs can be used as input for hydraulic modelling and simulation in a region characterized by flash floods.