Abstract
A stochastic model for generating hourly hyetographs has been recently developed, in the Cemagref of Aix-en-Provence, to be coupled with a rainfall runoff conversion modelisation. Thus, by simulation on very long periods, we obtain a lot of hourly hyetographs and flood scenarios that are statistically studied and used in flood predetermination problems. The extension of the model applying area has shown a heterogeneousness in the results. Therefore, modifications have been applied to the model to improve its performances. The different modifications added to the initial model, give very important improvements on the fifty raingauges studied on the French Mediterranean seaboard. Thus, we obtain a reliable tool, validated on a large area, giving many hyetographs and hourly flood scenarios on all the frequency scale, and used instead of a unique design storm and design flood. The approach allows a new cumulative probability curve extrapolation, which seems sometimes to be sub-exponential. Moreover, the analysis of many events per year, each presenting several realizations of the different variables of the model, seems to make the method more quickly reliable than a statistical approach simply based on fitting of the annual maximum values.