Decision Support System for hydrological risk assessment

The estimation of flood flows is of major importance for the design and management of hydraulic structures. Two main classes of laws are used in hydrology frequency analysis: the class D of sub-exponential distributions and the class C of regularly varying distributions with a heavier tail. No criteria were available for the choice between these two classes of the most appropriate fit, especially at extreme values. A Decision Support System (DSS) based on the characterization of the right tail of probability distributions, used in frequency analysis, has been developed. The DSS allows us to discriminate between class C and D. Note that the class selection has a great importance for the extrapolation. The use of the DSS on the Potomac River flood (USA), shows that the maxima series is best represented by a distribution of the class C.