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Influence of climate on the flood frequency distribution within a wide region of Southern Italy
No full textin Arni Snorrason et al. (Eds): The Extremes of the Extremes: Extraordinary Floods, IAHS Publ. no. 271
Influence of climate on the flood frequency distribution within a large region of southern Italy
No full textIn the theoretical derivation of flood frequency distribution as well as in the statistical regional analysis, climate plays a decisive role, being closely related to values and to patterns of variability of physically consistent parameters. We focused on the average annual number of flood peaks, Aq, and on the ratio of Aq over the average annual rate of rainfall events, Ap, as crucial parameters of extreme value distributions based on a Poisson process of occurrences. The link between climate and these statistical parameters is first empirically analysed and then explained as to how they relate to a characteristic water loss parameter dependent on climate, namely, a dimensionless loss factor f representing the storm rainfall threshold that determines if runoff is generated or not. Data from 20 basins in southern Italy, with hyper-humid to semiarid climates, show meaningful relationships between the degree of aridity and estimates of Aq/Ap and f
Sulla dipendenza dal clima dei parametri della distribuzione di probabilità delle piene
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Climatic control on the variability of flood distribution
Full text linkThe variability of the second order moments of flood peaks with respect to geomorphoclimatic basin characteristics was investigated, In particular, the behaviour of the coefficient of variation (Cv) of the series of annual maximum floods was analysed with respect to its dependence on physically consistent quantities. The results achieved were in fairly good agreement with real world observed characteristics and interesting insights on the relationship between Cv and basin size were found. It appears that Cv is controlled mainly by the climate and by some water loss features. Many observations reported in the literature show a decrease of Cv with basin area A, usually ascribed to the limited spatial extent of extreme events, which leads to a decrease with area of the Cv of areal rainfall intensity. An increase of Cv with the area is also sometimes observed for small basins. Such different behaviours were accounted for by the concurrent effect on two parameters that affect the Cv (A) relationship, representative of the way rainfall losses and effective rainfall intensity scale with the basin area
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