Methods and merits of regional flood frequency analysis

Regional flood frequency analysis (RFFA) is discussed in the context of regional smoothing of hydrological data, the concept of regional homogeneity is explained and the effect of inter-site dependence of flood data is discussed. A description of the principal features of twelve RFFA schemes is given, not all to the same degree of algebraic detail. Common elements of these methods are identified and the case in favour of RFFA is presented. The choice of RFFA scheme and the accompanying choice of distribution is discussed. The properties of RFFA methods and intercomparison of them as flood quantile estimators are referred to but the details reported by others are not reproduced here.